Hints & Tips

What Goes Wrong

© Brooke Clarke, N6GCE


Troubleshooting
Credit Card Fraud
What Goes Wrong
    HP 204B Oscillator
    R-1004/GRC-109 Receiver
    Quantic Q-5200/SM GPS Timing Receiver
    URC-68 Air Crew Survival Radio
    OE-254 Antenna
    PRC-77 Radio
    HP 241A Audio Oscillator
    TA-838 Mil Analog Phone  
    PP-8444A/U Battery Charger
    SG-1144/U Signal Generator
    SB-22 Switchboard 
    FTS4060 Cesium Frequency Standard
    Hard Drive Failure
    TS-1836C In Circuit Tansistor Tester
    Dead CRT Computer Monitor
    Philips 60PP9202 Projection TV Sudden Red Convergence Problem
Capacitor Failure
    PRC-104A Panel + Bent Connector 
    Electric Wall Single Oven Cold
    GE Electric Wall Oven Error --F1--
    Heathkit GC-1000 WWV/WWVB clock
Static & Electrocution
Printed Circuit Boards
    Replacing soldered in ICs
       Using Solder Wick
    Surface Mount Technology - seperate web page
    Not Soldering Connections
        Magellan GPS Commander
Reverse Engineering
Loctite
Rubber Parts
Car Radio Knob Broken
Cleaning
Rust
Lawn Mower
Storage 
Design Defects
Lap Top Li-Ion Battery
Precision Time & Frequency 
Kitchen Compactor Jam
Refrigerator Door Shelf Failure
Laptop Headset Connectors go Bad
Comfort Zone Stand Up Portable Room Heater Squeals and Stops
Battery Replacement
Water Misting
Hoover Upright Vacuum
Door Does Not Latch
Self Closing Hinge Spring Broken
Aeron Office Chair
Plumbing Stuff
    Kohler GP77759 Shower Mixing Valve
    Kohler Sink Valve Backwards
    Kohler Shower Temperature Hard To Control
    Leak in Sunpentown SB-2025L Fitting
    Outside Irrigation valves
    Hydro Swirl 96K6 Pump
    Refrigerator Water Filter
    SB-2025 Washing Toilet Seat
Electrical Wiring
    Circuit Breakers
    Power Line Cords
Electronic Construction Techniques - separate web page
Packaging for Shipment - separate web page

Troubleshooting

When there is a problem it's important to proceed in this order:

Credit Card Fraud

An email this morning from Capital One March 17, 2011 time stamped 8:43:
RE: Account ending in 0976

BROOKE,

One of the following changes was made to your Capital One® VISA SIGNATURE account:

1.
The mailing address was updated, or
2.
You've added an authorized user to your account

If you didn't make this change, please call us at 1-800-955-7070—we're available 24/7.

Thanks for using Online Banking.
All of my on line addresses (there are three different ones) were correct.
Calling Capital One I found out that someone had added a "SECRET" address in LA to my account, so I asked that it be removed.

A couple of hours later received a phone call from an Apple Coumputer store asking about my purchase of an Apple laptop computer for a little over $2000.  Needless to say I had not made that purchase.
Guess where they were going to ship it, yup, the address in LA, i.e. the SECRET address that Capital One had added.

What Goes Wrong

When Electronic Equipment is unused for years oxidation forms at the contacts.  This adds resistance to the joint and can cause the equipment to be DOA.  When I assembled the 2102 static RAM chips for my SWTP 6800 computer kit there was an instruction to NOT use sockets because the reliability of the socket was lower than the chip or solder joint.  By using sockets you would be creating a problem.  The more reliable sockets are Gold plated to avoid oxidation.

Below are some real examples.

HP 204B Oscillator

When received from eBay the oscillator did not function.  A check of the power supply showed that it was working fine.
After spraying the OFF-Range switch with Tuner Control Cleaner & Lubricant (Radio Shack - 64-4315) the unit started working.
The problem was oxidation on the switch contacts.

R-1004/GRC-109 Receiver

The receiver was DOA upon receipt from eBay.  A check of the power supply showed the correct voltages.
The resistance of each tube filament was checked when it was out and the tube was installed and removed from it's socket a few times.
All the filaments were about the same resistance.  The most common failure mode of tubes is that the filaments burn out and then will test as open circuits.  After assembly the receiver worked well.  The problem was oxidation between the tube pins and the socket.  I applied Lube Gel (an insulating Silicon grease) to the tube pins.  The idea is that at some points the metal pin will punch through the grease and make an electrical contact like wire wrap.  But the grease surrounding the small contact point will keep oxygen from degrading the electrical connection.   Note patent 5037566 Lubricating composition and method for making same is all about keeping Oxygen out of the grease.

Quantic Q-5200/SM GPS Timing Receiver

When received the LCD display backlight came on and the display showed 2 rows of all black 5x7 dots and two rows were not lit at all.
After removing the two main printed circuit boards and reassembling the receiver normal operation was restored.
The problem was oxidation between the one or more cable connectors and the mating contact.

URC-68 Air Crew Survival Radio

When received the radio was DOA.  After removing and reinstalling all the modules in their sockets a few times each the radio worked.
The problem was oxidation between the module pins and the sockets.

OE-254 Antenna

This antenna was installed quickly to do some tests on PRC-68 Family Radios.  When taking it down it was almost impossible to separate the mast sections.  The copper had oxidized inside the screw thread joint and much heat and force was needed to get them apart.  After polishing the male and female copper threads Radio Shack Lube Gel 64-2326   US 5037566 - Lubricating composition and method for making same. "...provides high corrosion resistance due to the absence of dissolved air and moisture.."] was applied to the joint before mating the antenna sections and Coax-Seal (Radio Shack: 278-1645) was used to seal the open part of the joint.

Lube Gel was also applied inside all outdoor RF coax connections to keep water out of the joints and prevent corrosion.
It may be that using Lube Gel in all of the above cases would prevent a future occurrence of the same problem?
Lube Gel appears to be a modern snake oil that can prevent many ailments.

PRC-77 Radio

After receiving this used but operational radio I cleaned it up using Windex, a toothbrush and a Rag-in-a-box both outside and inside.
As part of this process I found a number of screws that were either very loose or about to fall out.
The lesson is to give a close visual examination and that can best be done by cleaning.

HP 241A Audio Oscillator

The front panel had been bashed in.  This broke a plastic part that holds the radio buttons used to select frequency.  After removing and disassembling the front panel the plastic part could be removed and epoxied back together using J B Weld.  The neon power indicator was held on with one of those flat metal spring with teeth.  The plastic part of the indicator was broken by whatever hit the panel so the only thing to do was break the plastic behind the panel.  Hot melt glue attached the front of the plastic to the panel and holds the neon tube where it was.  From the front it looks original.  All of the button caps were removed and cleaned.  They had what may have been tobacco smoke obscuring the numbers.

TA-838 Mil Analog Phone

When received the phone did not work.  Opened up the case and disconnected the internal connector. Visual and olfactory inspection showed nothing amiss.  Reconnected the internal connector and reassembled.  Now phone works.  the connector must have had one or more poor joints.  Note this is a Gold plated connector.
It worked for about a year and it's dead again.

PP-8444A/U Battery Charger arrived DOA from eBay

Was sold as looking good and "as is" so no complaint.  After some troubleshooting it appears that on both charger boards C5 a Tantalum cap and U3 an MC34163 Inverting switching regulator have failed. thus causing a short (<2 Ohms) directly across the 24 VDC input to the charger board.  A shorted Tantalum cap was the problem with the SG-1144 Signal Generator.

SG-1144/U Signal Generator

The power supply had a number of shorted Tantalum caps.

SB-22 Switchboard

Before cleaning the resistance on one of side of the "D" battery holder was about 27 Ohms, way too high to pass the current needed for the talk battery or the buzzer. After cleaning it was below 0.01 Ohms.

After sitting in storage for years with the batteries removed the battery holder threads developed oxide.  When fresh "D" cells were installed the switchboard would not work.  The fix was to througherly clean both the male and the female threads of the battery holder and then apply Contax Oxide Inhibiting Compound (contains castor oil and carbon black)to all the threaded battery holder joints. I got this bottle at the OSH store in Sunnyvale, CA.

There was a time where the U.S. National Electrical Code allowed Aluminum wire in residences instead of Copper wire.  When joining Al and Cu wires a poor joint might result depending on how the joint was made.  To help solve this problem you can apply Contax.  So you'll find it in the electrical supplies section of a good hardware store.

FTS4060 Cesium Frequency Standard

This unit arrived DOA.   At the time I thought that it was shipping damage (and that is probably the case) since the other two boxed units that came on the same pallet worked fine but this one out of the box was dead.  Since it was no more than parts, I took every module and board that could be removed out and figured out all the connector and PCB pin outs.  In order to sell it as a parts unit it was reassembled and just for fun powered up.
It now locked and started working.  So cycling the connections may have  brought it back to life.

Hard Drive Failure

For awhile I was using removable hard drive "drawers" as part of a back up plan.  The idea was that you could clone the C: drive onto another hard drive.  Shut down the computer and move the cloned drive to the C: slot and retire the old C: drive as the backup.  Then power up the computer and run on the new backup.  The beauty of this approach is that you know immediately if the back up is good.  The other hard drive backup methods have a fatal flaw in that you only find out of the backup is good after your main drive fails and then it's too late.

The problem is that the drawer caddy adds another electrical two connections.  The original cable from the mother board now connects to the back of the cabinet that holds the drawer. and there's a plug and socket the allows the drawer to mate with the cabinet.  Then there's a short cable inside the drawer between it's plug and the hard drive.

A parallel ATA cable (IDE cable) has 40 (or in some cases 80) separate electrical connections the number of connections goes from 40 to 120.  If any of these has a problem the data on the disk can become bad.

So there's a huge reliability advantage to the new Serial ATA (SATA) interface because it greatly reduced the number of electrical connections.

A few months ago my 500GB IDE drive was nearly full so I replaced it with a 1 TB SATA drive.  Now I'm no longer using the hard drive drawers.  In the future I'll be going with only SATA drives.

TS-1836C In Circuit Tansistor Tester

This is an in and out of circuit transistor tester.  Although the DC battery check works, the beta test appears dead.  It uses a 1 kHz signal to measure beta.  The 1 kHz signal is coupled in many places by electrolytic caps.  There are 5 caps that are all 25 uF @ 10 Volts.  The AC impedance at 1 kHz would be about 6 Ohms, but the ESR meter is showing as high as 46 Ohms, almost an 800% error!  All the electrolytics in this meter need to be replaced.  After replacing the high resistance caps it still does not work.

By starting with the schematic diagram and erasing all the switch contacts and are not being used and then anything in series with them the resulting schematic has missing connections.  Very strange.  Although it may be that lines were erased that should not have been, repeated audits have not found them.

If you have one of these that's working please let me know.

Dead CRT Computer Monitor

Symptoms: burning electronic part smell.  Failure to turn on.
Failed Component in CRT
          Computer MonitorA visual inspection found this burned out component.  The schematic symbol under it looks like the letter "Z".  It's located at the AC mains input to the power supply.  Right behind it is a bridge rectifier and a 330 uF cap.  The coils to the right are probably part of the line filter network.  The two blue wires go to the front panel, not sure why since the  front panel (left of photo) On-Off switch has a plastic connection to the line switch (to the right of photo).

What is the dead part?
It might be series connected (inrush current limiting) or shunt connected (overvoltage protection  MOV).
When trying to trace the PCB wiring using the DMM in continuity mode a chunk of the PCB (around the burned area) fell out.  So I've scrapped this monitor.

I'm thinking it may have been the problem or the cap behind or a nearby cap may be bad.  The ESR checker will be used, but the first order of business is to find out what this is.

Note the rectangular black plastic part just behind the split component.  The solder connection looks like a donut, i.e. it's not wetting the lead, a poor quality joint.

Philips 60PP9202 17 Projection TV Sudden Red Convergence Problem


Philips 60PP9202 Projection TV Main
                Board with Convergence ICs
This is the  main board.  The large fined heat sink holds the two convergence STK392-120 ICs.  Each of them and three channels so it takes two for a balanced drive.

There must be a hundred cables that need to be removed to get that board out of the set.

Beside each board connector there is a reference number that can be written directly on the ribbon cables, but all the others will need some kind of label.
Philips 60PP9202 Convergence
                STK392-120 In the photo at left it appears (needs to be confirmed after removing the STK392-120) that no heat sink compound was used when the rear chip was installed at the factory.  The front chip clearly shows a bead of white heatsink compound.  There is heat sink compound behind the rear chip, just not as much.

It would be nice to have detailed instructions for the replacement of the two convergence driver ICs and the realignment.  If you have it or know where I can get it please let me know.
Philips 60PP9202 Projection TV main
                PCB with two STK392-120 ICs
To remove:

I already had the large rear cover and the cover around the three projection lens assembly removed and the panel to it's rear,  maybe or maybe not required for this.

remove rear connector panel.  In addition to the screws on the outside there are a couple on the inside and the nut on the "F" connector.

Remove the centeral bridge to get better access for cable removal.

Remove all the cables (seems like a hundred), labeling them all so they can be replaced.

Remove (maybe 3 or 4_ screws holding down PCB.

Lift the tabs on the right and slide the PCB out the back.

The spring clips have been removed from the two STK392-120.


STK392-120 Inside view
Using solder wick AND adding liquid flux the pins were easily desoldered and the ICs just dropped out.

Breaking the plastic case shows the inside of the STK392-120.  Appears to be all discrete parts, no ICs.  Note the base is the aluminum plate heat sink.

The leads got mangled in the process of removing the plastic case.
Fried Resistors near STK392-120Note the lower resistor is marked 6 (the rest has been cooked off) the others nearby are marked 6R8 or 6.8 Ohms.  There are 12 of these always in pairs.  The pairs are wired in parallel and so measure about 3.4 Ohms true or 3.6 on the DMM because of the test lead resistance.

These measure in the Meg Ohms, i.e. totally fried.

Now 27 Jan 2009 to wait for the resistors to be delivered. 

The two fuses tested good.

The  resistors are grouped near the three connectors for RED, BLUE and GREEN, not the STK392.
After replacing both STK392-190 chips the TV was just as bad as before.

It was much faster to pull the main board since all the cables were labeled.

With no documents it the drill was to check all the resistors.  These were found on the other side of the board from the STK392 near the connecor marked RED.
Installing the two 6R8 resistors fixed the convergence problem.  But while doing the convergence using the manual procedure with  a grid of 5 x 7 "+" marks and watching some DVDs a blue halo was noticed surrounding bright subjects.  This is very likley due to contaminated coolant on the blue CRT.
Philips 60PP920 Blue HV anode cable
                source
It looks like the complete blue assembly can be removed by removing the 4 screws from the sheetmetal bracket and disconnecting all the cables and unplugging the PCB.

All that has been done, except removing the anode HV lead at the main PCB rather than at the CRT.

How to unplug it?
Philips 60PP9202 Blue CRT Assembly

Philips 60PP9202

Blue CRT Assembly



The anode HV wire unplugs from the three way HV splitter and the yellow ring stays as part of the splitter.

Anyway that's what I hope.

Just above the lens, facing to the right is a cover held in place by 4 screws.  This is the bladder compartment.  At it's center is an inspection hole.

The blus stripe on the connector next to the HV wire was put on by the factory.
Philips
                60PP9202 Blue CRT Cooling Fluid Filler Plug
Philips 60PP9202 Blue CRT
Cooling Fluid Filler Plug

The filler plug is opposite to the bladder.

What does "+0.38" Mean?
Let me Know.

The Yellow sticker says:
Delta DigitalTM 260
Covered by U.S. Patents
3M Precision Optics Inc
p/n 313503750721

The fluid is just under the plug so a way to suck it out would be good to avoid spilling it.

"Projection Tube Coolant" is the title of the eBay item that's on order.

Philips Blue CRT Coolant is Cloudy
Philips Blue CRT Coolant is Cloudy

The photo does not show the backscatter as well as you can see it with you eye.   As the Mini Maglight is focused you can see the bright and dim beams change shape.

The thick fluid also has a yellow tint.

Remove plug, place small finger over hole, ,turn upside down over tray, remove finger and while tipping slightly in all directions empty fluid.
Denatured Alcohol is no longer a drug store item.  But is carried by paint stores like Kelly More.  It's the solvent recommended in the factory manual for cleaning the fluid chamber.  Rather than disassemble the chamber I'm going to rinse it many times using the Denatured Alcohol.  Three times yesterday.  Leaving the plug off so it can evaporate.  An ear irrigation rubber bulb makes a nice tool to put the Alcohol into the small filler hole.
9 Feb 2009 - the bottle arrived and is labeled "Fluid Coolant"  not "Projection Tube Coolant".  I wonder if it's used in some other application?
The ear irrigation rubber bulb is a good tool to put the fluid into the small hole.  If you look into the lens you can get a very good idea of how much fluid is there from maybe 10% to 90% of capacity.   When the chamber is almost full you can see the distortion on the surface as new fluid is added.  The plug has a projection that displaces some fluid when it is installed, probably as a way to prevent over filling.

It only takes a few minutes to reinstall the CRT assembly into the set since all that's required is to put in the 4 screws that hold it in place and plug in the cables and the small PCB.

Now when a DVD starts the blue "DVD" no longer is surrounded by a blue cloud and at the top of the screen there are horizontal bands of blue that are visible (which before was just a blue fuzz ball).  The optical and electrical focus on blue needed tweaking and now the blue convergence can be done.  The only problem left is to tweak the blue intensity.  The picture looks great and skin tones are great.

10 Feb - A helper can push the navigation ring on the remote to keep the manual multi point convergence big + moving (to prevent the timer from turning it off) and covering one of the two active CRTs then you can adjust the electrical and mechanical focus on all three tubes.  By watching a good movie the blue intensity was adjusted then after watching more movie it was tweaked.   Now the image is as good it gets, much better than prior to the red convergence failure.

Pressing and holding Mute on the remote and pressing any button on the front of the TV causes it to go into User Service Mode and no error codes were shown.
Major Components
Philips
                60PP9202 17 Major Components
After reading about the failure of the convergence amplifier ICs in projection TV sets this seems the most likley cause of the sudden red color failure. 

The Philips web page will not sell me a service manual, only "authorized" dealers can buy it.

Now looking for a source of the STK392-120 chips.  I found two eBay sellers of this chip.
One offers a 2 pack for $12.99 but does NOT mention the brand name.
The others offer them for $12 to $15 each including USPS mail delivery, I got a couple of these.

Home Theater Shack - Link to my post #222 asking about the Service Manual and where to get the chips. Post moved to Philips 60PP9202.

The fundamental problem may be the choice of thermal grease.  The early formulations have a thermal resistance vs. time degradation that the newer types no longer have.  For example Wakefield 126 (accessories.pdf 1.3 MB) Thermal Joint Compound is twice as good as the old 120 compound after 6 onths of cure time.  Found this when working on a 7 Watt LED.

Ohm Meter Readings on the STK392-120

Pin
Function
7405 rear
7404 front
1
Sub Gnd
0
0
2
Gnd
0
0
3
Muting
1.6M
10k
4
-PreVcc
1.4M
1.4M
5
+PreVcc
2.6M
2.6M
6
Ch1 +In
3.2k
3.2k
7
Ch1 -In
3.3k
3.3k
8
-Vcc1
1.5M
40k
9
Ch1 Out
104
104
10
+123Vcc
0.5
0.5
11
Ch2 Out
104
104
12
-Vcc2
380k
1.4M
13
Ch2 -In
3.3k
3.3k
14
Ch2 +In
3.3k
3.3k
15
Ch3 +In
3.3k 3.3k
16
Ch3 -In
3.3M
3.3k
17
-Vcc3
2.4M
2.7M
18
Ch3 Out
3.2M
104
All the outputs are 104 Ohms except for 7405 (rear IC that had minimal heat sink compound) which is 3.2 M Ohm.  It's blown open and Ch3 is probably Red.  Note that pin 18 is close to the center of the heat sink and so will have some heat from the front chip.  If heat is the problem then you would expect Channel 3 of the rear chip and/or Channel 1 of the  front chip to go since they will be the hottest ones.
The other values are marked red because they are different for the front and rear ICs.

Dec 2009 - When upgrading my Home Theater and watching YouTube the blue was way off convergence and the red was a little off.  It turns out that the new A/V receiver was feeding the projection set 1080i video and when the repair was made the alignment was not done for that resolution. While feeding the set with a YouTube video the multipoint red and blue alignments were done requiring a number of iterations.  After watching a few YouTube videos another alignment was done.

When a Blu-ray disk is played and the output fed to the A/V receiver using component video the projection monitor is fed 1080i video.  The image is FANTASTIC!

Service Manual

Available as .pdf from Manual Zone - Has Parts lists for 82 model numbers but there may be many duplicates. 1,848 pages.

Patents relating to Rear Projection TV

 by 3M Innovative Properties Co (seem to be about the screen not the optics)
6163402 Rear projection screen, 3M Innovative Properties Co, Dec 19, 2000, 359/443 ; 353/74; 359/454; 359/460 - made for HD TV
6204971 Glass microspheres for use in films and projection screen displays and methods
6317263 Projection screen using dispersing lens array for asymmetric viewing angle, 3M Innovative Properties Co, Nov 13, 2001, 359/443; 359/460 -
6417966 Rear projection screen using internal reflection, 3M Innovative Properties Co, Jul 9, 2002, 359/453; 359/460 -
6449089 Rear projection screen with enhanced contrast,  3M Innovative Properties Co, Sep 10, 2002, 359/454; 359/460 -
6515798 Rear projection screen, 3M Innovative Properties Co, Feb 4, 2003, 359/443; 359/449 - 

Capacitor Failure

The idea with a capacitor is to have capactive reactance that's low compared to the rest of the circuit.  The equivalent series resistance (ESR) of the capacitor should be considerable lower than it's capactive reactance.
Xc = 1/ (2 * PI * F * C).  Values shown in table below are at 60 Hz.

ESR-Micro Combined ESR & Cap Meter

Capacitors - new web page
ESR micro Capacitor
        tester

EVB ESR Only Tester


EVB ESR Tester


I have made some modifications on the stock tester so that it can be used to measure the ESR of batteries.

(1) The two large protection diodes need to be removed from the PCB.  They are located near where the banana jacks are wired.

(2) A SPST normally open push button switch is added near the tip of one of the test leads and in series with the lead.  Across the switch place a 470 ohm resistor.  When the probes are first connected to a live battery the 470 Ohm series resistor pre charges the internal non polarized blocking caps without hitting them with a really fast rise time pulse, thus tending to protect the internal circuitry.







On the face of the meter is a table showing normal ESR values for capacitors as a function of capactance and voltage rating.



10 V
16 V
25 V
35 V
63 V
160 V
250 V
1 uF
x
x
5
4
6
10
20
2.2
x
x
2.5
3
4
9
14
4.7
x
x
6
3
2
6
5
10
x
1.6
1.5
1.7
2
3
6
22
3
8
2
1
0.8
1.6
3
47
1
2
1
1
0.6
1
2
100
0.6
0.9
0.5
0.5
0.3
0.5
1
220
0.3
0.4
0.4
0.2
0.15
0.25
0.5
470
0.15
0.2
0.25
0.1
0.1
0.2
0.3
1000
0.1
0.1
0.1
0.04
0.04
.15
x
4700
0.06
0.05
0.05
0.05
0.05
x
x
10000
0.04
0.03
0.03
0.03
x
x
x

Note that the Impedance of all capacitors is a function of frequency.  As the frequency goes up the capacitance will decrease because of the inductance of the leads and maybe the capacitor itself.  Typically the smaller the value of capacitance the higher in frequency it's still a capacitor.  So it's common to see a number of capacitors in parallel.


Electrolytic

It's the nature of electrolytic caps to have the electrolyte evaporate.  How fast that happens depends on how well it was sealed.  Another problem showed up around 2002 when a defective electrolyte was used in a very large number of caps resulting in failures after 250 or more hours of actual operation.  Low-ESR Aluminum Electrolytic Failures Linked to Taiwanese Raw Material Problems.  The failure mode is to blow the vent cap and spew electrolyte.  The electrolyte will damage printed circuit boards beyond repair and that can lead to smoke and or fires.  Electrically the cap looks like an open and in some cases the guts are blown out of the can and it's literally empty.
Electrolytic
          capacitors
#
Cap uF
WVDC
Xc60
ESR
ESR/Xc %
0.5*C*V*V
The formula columns are an attempt to come up with a way to predict the ESR for a given chemistry cap.  Not working yet.
1
40 200 66
0.64 1
0.8
2
500 50 5
0.19
4
0.625
3
2200 6.3 1.2
0.23
19
0.04
4
39 16 68
0.30
0.4
0.004









Tantalum

Tantalum capacitors offer a higher C * V product than electrolytic capacitors in  the same volume, or more commonly in a smaller size package.  When introduced they were adopted by the military and commercial electronics industries.  But if improperly installed (polarity reversed) they behave more like firecrackers and immediately explode.  Also if subjected to spikes of voltage or current they will be degraded or fail.  The failure mode is to short out.  This causes some up stream component(s) to fail by burning up possibly starting a fire or destroying a printed circuit board.
Tantalum Caps These are tear drop or dipped Tantalum caps and are the type I've seen most as dead shorts.

#
Cap uF
WVDC
Xc60
ESR
ESR/Xc %
5
10
35
265
1.2
0.5
6
10
25
265
0.35
0.1

Trimble 16768-80 GPS receiver
                  Power Supply
Trimble 16768-80 SLGR GPS Receiver Power Supply

#
Type
uF
WVDC
ESR
C5
Tan
10
35
0.42
C1
Al El 220 63 0.39
C4
Tan 220
10
0.05
C3
Tan
?
?
0.17

C4  Hermetically Sealed Axial Tantalum
marking:
M39003
09-0221J
+220uF
10% 10 V
31433
9101AM K

PRC-104A Panel Short


PRC-104A (RT-1209A) Front Panel
                  Shorted Cap PRC-104A (RT-1209A) Front Panel Shorted Cap(s)

Marking on the rear cap is:
CX06M685M
8848VME

Dipped Radial Tantalum Capacitors 35volts 6.8uF 20%

Capacitor, tantalum,
6.8 uF, 20% Tol,
-55/+125C, 35V@85C, 23V@125C,
E, Micro-Miniature: Size E, (E x 3.3" x 7.87" LxTxH), 
Pitch is 0.2", W=0.228", T=0.126", H=0.30"
Bulk, Bag (180 pcs),
6% DF, 2.5 Ohm ESR, 3 uA Leakage

There are two of these caps connected in parallel and they are across the main DC power supply.
Another PRC-104A panel had this exact failure.

A voltage rating of 35 VDC maybe is too close to the input voltage range of 9 to 32 VDC?
A 50 VDC 6.8 cap is available T491D685M050AT that might fit the space.


After replacing the two caps the blown fuse problem has gone away.
Pressing the LIGHT button turns on the back light.
But the LCD is blank and the handset does not have white noise.

Bent Connector

PRC-104B AUDIO Connector Angled Visual inspection shows that he AUDIO connector has been bent or hit causing it to sit at an angle and it's support PCB has broken solder joints on the ground pins.
 PRC-104B
                  Panel Opened, AUDIO con freeThe audio connector has been separated for inspection.  The two new Tantalum capacitors are the round yellow ones.
PRC-104A
                  Cracked Front Panel (2 places)
PRC-104A Cracked Front Panel (2 places)


Static & Electrocution

Electrocution

Often static electricity is blamed for what I call electrocution.  For example, I was asked to investigate why the yield was very poor on an expensive polar discriminator assembly that used four back diode detectors on each housing.  Static discharge was the assumed cause of the problem, but the real problem was a soldering iron that had about 15 VAC on the tip.  Back diodes can be blown with only a few volts.  The work bench had maybe a half dozen soldering irons (all expensive anti static grounded tip type) and only when the defective iron was used would the diodes be blown.

Static

Some definitions

Antistatic: Preventing or inhibiting the buildup of static electricity.
Since static electricity is generated by moving electrons from one insulating material to another the current involved is very small so a high value resistor between the two objects can easily equalize the voltages and prevent buildup.  A pure plastic bag that can generate static electricity can be treated in a number of ways so that it has a high resistance and then will not generate static.  This is an anti static bag.

Electrostatic Discharge (Wiki Talk): The sudden and momentary electric current that results when an excess of electric charge, either stored on an electrically insulated object or on an isolated conductive object, finds a path to an object at a different electrical potential (such as ground).  
Getting shocked in a warm room in the winter time when touching a metal object is because of ESD.
Lightening is an example of ESD.

It's very important to see the distinction between these two ideas.

I sit on a chair with plastic wheels in a room with wall to wall carpet.  I used to use a "chair mat" to get a hard surface so the chair wheels would roll, but plastic wheels on plastic is a static generator and often I would get a static shock.  Using antistatic spray would help but was not a cure.  Placing a sheet of plywood over the mat (could have removed the mat) solved the problem.

When working on a PC I leave the power cord plugged into the wall.  This has a danger factor in that the power switch has hot line voltage and maybe some spots on the power supply are line hot.  But it also connects the chassis to line ground so that if you touch the chassis before you touch any static sensitive device the static will be grounded.

Wrist straps are not good grounds, but rather have a 1 to 10 Meg Ohm resistor in series between the human and ground.  This way you are not grounding someone and making a human electrocution possible.  If you want to make your own ground strap by using a piece of copper wire and a ground lead, be sure to insert a 1 MegOhm resistor in series.  

Many companies that work with static sensitive components, like microwave parts or disk drives, have special flooring that is conductive and the workers wear shoes that are conductive or use heel straps that make a high resistance path from the floor to the ankle.  This way a person walking does not build up a charge.  Also the chairs and stools have grounding chains always in contact with the floor so a moving chair does not generate a charge.

When packaging a static sensitive component many people make the mistake of thinking that using an "antistatic" bag will protect the component.  THIS IS NOT THE CASE.  An "antistatic" bag will not generate static but does not protect from static. 

It is easy to destroy the component while it is in a sealed "antistatic" bag.  Just walk across a carpet on a dry day and touch the top of the bag while it is sitting on a metal work bench.

 The proper way to protect the static sensitive component is to wrap it in Aluminum foil or use one of the conducting Faraday cage type bags.

PS Magazine 2004 Issue 623 page 42 has published this information about what antistatic means. (PS I'm in Ukiah, CA, not San Diego) 
EEVblog #3 – Anti Static Myths Busted -

Office chairs that have plastic wheels rolling on carpet protectors make excellent static generators.  They are a real problem around computers.  It's better to get a sheet of 3/4" plywood for the chair to roll on.

Printed Circuit Boards

A way to get a double sided board with vias is to use Express PCB.  They have a prototype service that will supply 3 boards that are 3.8 x 2.5 inches and have tin-lead reflow but have neither Silk screening, solder masks, routing nor multi-layers.  There are a limited number of drill and pad sizes.  You can put a number of smaller boards on one and separate them yourself using a Tungsten carbide tipped scriber (General Tools Model 88CM, Catalog No. GEN-31116 ).  A straight edge is needed for the first pass but all the succeeding passes are in the groove.

In the 1960s we used shoe eyelet's to connect the top and bottom PCB traces in double sided boards.  They were installed and formed using a motor powered machine then hand soldered.  This was a military approved way of PCB construction and much easier than soldering a wire and cutting off both ends.

2002 - update on cutting printed circuit boards.  I got a single speed skill saw at Wal-Mart, chosen for it's low price and that fact that it had a couple of nuts as part of the flat surface.  By drilling a hole through the 1" thick workbench top and making a short slot for the blade, then mounting the saw underneath the workbench using a couple of flat head screws, with only the blade sticking up through the slot I now have a reciprocating table saw.  By using a fine tooth metal cutting blade you can separate 25 to 100 PCBs.  This bench mounted $10 saw turns out to be quite handy.  The screws that pinch the blade turn out to be an M4 thread and have been replaced.  It takes a lot of finger strength to cut small boards since you need to hold them down very firmly or they will jump up and down with the blade.  It makes a lot of dust that you should not breathe.  It takes a little more than 50 mils for the saw kerf.

2006 Update - A small 8 inch Mini Shear Break designed for working sheet metal does a nice job of cutting 1/16 inch PCBs.  Although I think I know why the first one is not broken waiting for parts to arrive from China, I've received an email from another user that said his would not cut boards out of the box.

Replacing soldered in ICs

After having identified a bad IC that's soldered into a PCB I used the following procedure.
Cut all the IC leads using diagonal cutters.  It took a couple of passes to get them all cut on one side of the IC.  Then bend the IC up and unsolder and pull each lead one at a time.  Then press the IC down and cut and desolder each of the pins on the other side.  This destroys an IC that was bad already but greatly reduces the chances of damaging the PCB.

3 May 2006 - Next using a solder sucker clean out all the holes.  Install the new IC and solder in place.  This may not be so easy.  Sometimes neither solder wick nor solder sucker will get the solder out of the hole.  If a piece of wire that's the right size for the hole is chucked into a Dremel tool then cut off so that only a board thickness plus a little is above the chuck face.  It can be used as a drill bit on the highest speed.  Another option that has also worked for me is to use a sewing needle held in a pin vise to push a hole into the solder, sort of swaging.

Using Solder Wick

6 May 2006 - If just prior to using the solder wick you wet about 1/4" with RMA flux it will work much better.  This may be for two reasons.  First the liquid conducts the heat better than air and second, the flux cleans the solder wick of oxides allowing the solder to bond easier.  This makes the difference in being able to get solder out of small diameter holes or not getting it out and needing to drill as above.

Flux

The key property of solder flux is that it's boiling point is higher than the melting temperature of the solder.  This makes for excellent heat transfer.  The shape of a soldering iron tip is typically conical or cylindrical and so touching the iron to a wire or circuit trace makes for a small contact area and poor heat transfer.

If a small amount of flux is applied and the iron located where flux is present then you have much better heat transfer.  If there's a hole with solder and a component lead you need to fill the hole with liquid flux to transfer the heat to the solder.  If you just flux the solder wick you may or may not be able to get the solder out of the hole.

Flux pens and a handy way of applying liquid flux, but don't order them on the same order as other items because it will slow down your whole order since they are shipped as a hazmat item.


MS Connector de
            soldered with Wick + Liquid FluxThis is the construction of the A.C. Power cord for the M455-1 Power Supply.  The connector was second hand, i.e. all the cups were full of solder.  The wick was flat and a little wider than the O.D. of the pin but using tweezers it could be formed into a shape that would fit into the solder cup (after using the wick in the normal way to get down to the solder cup).  Then using a very pointed iron (the one used for SMT soldering) and trapping the wick between the iron an the protruding part of the cup the solder was sucked completly out of the cup. 
Flux & Solder Wick
It's very important to add liquid flux to the solder wick to transfer the heat.  This will make the difference between no wicking and wicking!!

The "A" pin at about 2 o'clock is the one that's been cleaned, no point in doing pins that aren't going to be used.

The black jaws are on a Panavise Jr.

Also when using shrink tubing in very tight quarters like this don't use a size that's a tight fit because when the wire insulation distorts you will not be able to pull the tubing over the joint.  A pair of tweezers was used as a heat sink to keep the shrink tube from shrinking.  The tweezers were held closed by a spring like used in the 257477BA Battery Adapter.

using Panavise Jr to
            hold connectorHere the Panaviswe Jr. is tipped on it's side and the rotation of the ball clamp has been adjusted so that there's a three point support (the base, the end of the adjustment arm, the  tip of a jaw) that's stable.

This is a great way to hold connectors while they are being assembled.

Soldering Surface Mount Devices - seperate web page on Surface Mount Technology

Soldering Iron Tip Maintenance

When finished using a soldering iron I used to clean the tip and power down the iron.  This results in the tip oxidizing and getting pitted.  Much better to clean the tip and put a big glob of solder on it just prior to power down.  Also the modern tips come with a silver colored plating, they are not raw copper and this helps maintain the tip, so these should not be filed.

Magellan GPS Commander

The factory did not solder 5 joints on this prototype.  This is the kind of mistake that may have cost them a contract.  This GPS receiver has a number of jumper wires on the Printed Circuit Board that were put there to correct errors in the first generation PCB layout, so this was intended to be a working unit, not a dummy.
Unsoldered joints Magellan
          GPS Commander

Reverse Engineering

Naming

Most of the equipment that I have reverse engineered made use of printed circuit boards.  If the board has part ID information you can use the same part names, but if it does not (most of the time) they you need to name each part as well as have a way to identify each lead.  Lead identification for ICs is easy since they have standardized pin numbering, diodes have an anode and cathode, but resistors and other parts don't have lead specific markings and so you need to keep track of which end goes where.  This can be done by using a flat bed scanner to make color images of each side of the board and then adding part names, like shown in manuals.

Conformal Coating

Often it's necessary to use a continuity checker (beep Ohms mode on a DMM) to find out what's connected to what.  This is especially true for multi layer boards.  When working with military boards you will find that they often have conformal coating that is thin and transparent.  So when you place a probe tip on top of what appears to be nice shinny solder you will NOT make electrical contact.  A quick check is to put both probes on the same pad, yet not touching each other.  If there's no continuity then you know you're working on a coated PCB.  One way around this is to push and/or rotate the probe to punch through the coating and into the solder, but the same pad may need to be probed many times and this really chews up the pad.  A better way is to use a large sewing needle held in a machinist's pin vise.  The meter probe can be put into the hollow metal handle or connected with a clip lead.

BEEP Mode of DMM

The DMM may BEEP when the connection is not really a metalic path but instead is a low resistance path.  So it's better to not use the beep function and instead look at the Ohms reading.

Caution

When reverse engineering some thought needs to be given to possible DC shorts.  When working on the FS5000 Spy Radio I smoked a PCB trace that was on one of the interior layers.  This could have been avoided by fusing my test fixture DC power leads (both the hot and ground).

Cable Testing

When reverse engineering a cable be sure to look for jumpers that connect multiple pins on the same end of the cable.  These will show up if you test all possible combinations of pins at both ends of the cable.

Loctite

Loctite is great for keeping screws from coming loose, BUT should not be used near plastic parts.  For the very first production lot of my 2577BA Battery Adapter I used Loctite 222 on a 6-32 screw that went into an Aluminum spacer.  BUT the 1/8" thick plastic sheet between the two showed severe cracking when the Loctite set up and the whole batch had to be scrapped.  I think what happened was some Loctite got into the space between the screw and the plastic and when it set up it expanded and destroyed the plastic.  Needless to say I don't use Loctite in this application.

Rubber Parts

Rubber (and synthetic equivalents) biodegrade.  Air and/or water will cause them to disintegrate.  Insulation will turn to dust and hoses, gaskets, O-rings, etc. will fail.  In older automotive applications this is the most common failure mode I have seen.

My 1929 Rolls Royce and the 1934 Rolls Royce used steel tubing between the vehicle frame and the engine where today a rubber hose is used.  They did this by forming 3 or 4 turns about 3 " in diameter so that the tubing would never be stressed past it's elastic limit as the engine rocked back and forth.  Of course the engine did this only on acceleration or engine braking, when idling you can balance a Nickel on top of the radiator.

The O-rings between the steel cylinder sleeves and the aluminum block of the all the RR cars with a V-8 engine is a real disaster.  It's a certanity that one of the huge number of rubber hoses carrying water or the rubber seal in the water pump that also has to act as torque stop, will fail while you are under way resulting in the engine block over heating.  Overheating those cylinder seal O-rings results in failure to seal the water or oil.  If it's the upper O-ring that failed you will get water coming out of the weep holes in the block since there are two O-rings at the bottom, the lower O-ring seals out crancase oil, so if oil is coming out the weep hole it means the bottom O-ring has failed.  Needless to say replacing the O-rings requires  major engine work.  If the aluminum block that's about 1/8" thick between cylinders cracks then it can NOT be welded since the aluminum is plastic impregnated.  But you migh be able to use an epoxy, didn't try that. 

Car Radio Knob Broken

There are small knobs that can be popped out and then pulled out to set balance, bass and treble settings.  The plastic knobs seem to fall apart.
Repaired using J-B Weld epoxy being careful to keep it out of the central hole.  You can see some gray epoxy in the after photo.
Intrigue Radio
                  Bass/Trebble Knob Broken
Intrigue Radio
                  Bass/Trebble Knob Repaired




Cleaning

In order to make images of equipment I use a digital camera or color flat bed scanner.  Both of these methods show up every spec of dust so cleaning is needed to get good images.

Dirt

Dirt is the most common thing that needs to be removed so the first cleaning step us to use water  to wet the dirt, a tooth brush, tooth pick, small brush, pipe cleaner to scrub a little and a clean dry paper towel or tissue to wipe dry and clean.  Often knobs need to be removed to clean under them.  Engraved labels often have dirt covering the white paint and need extra scrubbing.

Very Old Masking Tape

DE-Solv-It , Contractors' solvent available at K-Mart - removed tape from a BC-611 radio that nothing else could touch.

Tape adhesive

This web page has a number of methods to remove tape adhesive as well as other stuff.
Goo Gone™ (Magic American Corp.- Cleveland OH) has received a number of recommendations on the Tek list server also works for decomposed foam.

Rust

Oxygen, moisture  and about anything can combine to make corrosion.  There are many commercial rust remover products on the market.  Many use phosphoric acid. (Wiki: RustRust Remover).  Renaissance Metal De-Corroder says it's made of : Amine comples of hydro-oxycarboxilic acid.  But the only references to the key indegrient are ads or references to this product.  It has the look and feel of phosphoric acid.  Available from the Gemmary.

If paint primer is applied to bare metal it affords NO protection from rusting.  Primer is by design a porous coating so the the paint overcoat will bond well.  Leaving a car outdoors with just primer is a great way to rust it (ask how I know this).  The second time I used a special paint made for ships called Corroless.   I picked this brand after reading the paint shoot out test results in Skinned Knuckles magazine since it got the highest ratings.  Rustolum and POR15 were not as good.

Vapor Phase Rust
          Prevention paperI've recently been doing things that involve metal working and a number of times I've come across vapor phase rust prevention (aka: Volatile Corrosion Inhibitors or Vapor Phase Inhibitors) papers.  There's a brown sheet of paper behind the plastic laminated cal certificate in the box lid of the pin gauges.  That's the special paper.  My local machine shop ships metal parts to me with some of the paper in the packaging.  It has some shelf life so is not a permanent solution, but one worth knowing about.

4604227 Vapor phase and surface contact rust preventive composition, Stauffer Chemical Co, Aug 5, 1986, 252/389.2 ; 252/389.61; 252/392; 508/399

Protective Packaging carries moisture barrier bags and Vapor Corrosion Inhibitors paper.  Their web pages have a lot of good info.

When rust forms in a threaded fastener it becomes very difficult to remove the fastener.  Many people use WD40 but  that's the wrong thing.  WD stands for Water Displacement which is what it was made to do.  For getting stuck nuts, bolts or other items loose a penetrating oil like Kroil, is what works best.

For removing rust from metal parts that are not to be painted consider Evapo-Rust.  For a user report see VY2AC on Prince Edward Island - Ridding Parts of Rust!

Lawn Mower (Scott's Model 22815x7A)

Lawn Mower (Scott's Model 22815x7A) walk behind
                  self powered lawnmower Lawn Mower (Scott's Model 22815x7A) Front Wheel
                  B&S p/n 672441






I put this article just below Rust because that's one of the problems the lawnmower had after sitting outside for a number of years.
This is a self-powered walk behind lawnmower with a vertical shaft engine and single cutting bar.  6.0 HP B&S 4-cycle engine.

 There were a number of problems:
1) When the starting cord was pulled it failed to retract.  It turns out nothing was broken it was just a lot of friction stopping it from retracting.  The fix was to squirt some Kroil penetrating oil into the joint between the rotating part and the fixed part (a circle about 5" in diameter).  This probably could be done without any diss-assembly.
2) The drive belt had many cracks and broken parts and was very stiff and needed to be replaced.
    37x105,  John Deere p/n: M77167
3) The drive axle was frozen (would not turn, would no come out to allow Removing and Replacing the drive belt).  It was necessary to remove wheel support plates to free the axle.
4) the bolts holding the wheel support plates were frozen (rusted) together and Kroil did not help so when torque was applied one bolt snapped, so 4 replacement bolts and nuts were purchased along with the new drive belt.  Loctite 222 was used when installing the new nuts and bolts rather than using lock washers.
5) the teeth on the inside of one of the drive wheels have been almost all chewed off.  I've ordered a couple of new wheels from eBay using the B&S p/n 672441.

Storage

When in storage anything is subject to oxidation, humidity and temperature cycling.  Military packaging typically involves sealing the product in an air tight waterproof bag.  This limits the oxygen available to what was there when the bag was sealed, once that's used up there will be no further oxidation.  Also the humidity is constant inside the bag.

You can get these same benefits simply by sealing things into Zip Lock plastic bags.  It helps if you zip up all but the last 1/4" then compress the bag to get out as much air as possible then zip up the last bit.  This also minimizes the space that the bag occupies.

Try to place items in storage where temperature cycling is minimized, but this is not always an option.

Design Defects

In some cases it is sold as a "Feature". 

HP Doppler Radar Module

In some cases it kills the product or manufacturer.  Long ago HP came out with a doppler radar module.  The idea was to hook up an antenna, supply DC power and get the audio doppler signal out.  It involved a lot of specialized construction and tooling.  But there was a design defect that greatly degraded the signal to noise ratio compared to a different topology.  The product disappeared from the market.

LCD Backlight in PRC-126

In other cases is just fixed.  The first PRC-126 radios added a back light to the LCD display and it also was supposed to be night vision goggle compliant.  The designer placed a very dark green filter above the LCD and this worked great for night vision goggle use and I'm sure that's where all the effort was focused since this was a new high tech area, BUT you could not read the LCD in daylight.
Later radios fixed this by placing the dark green filter between the back light and the LCD.

Rolls Royce V8 engine

The Rolls Royce cars with V-8 engines use an aluminum block and steel cylinder liners.  The aluminum thickness between cylinders is maybe 1/8" or less.  When (not if) the rubber O-rings sealing the steel liners to the block fail (see Rubber Parts above) the engine overheats causing irreparable cracks in the thin block wall.  The last I heard Rolls was going to buy engines from BMW.  It's too bad that the company has been going down hill ever since Mr. Royce died.  The cars he designed were built to be reliable.  RR won many races, not by being fast, but by finishing.   That's why Lawrence of Arabia used the PII chassis as the bases for armored cars.  The PII was also featured in one of the Indiana Jones movies.

Fluke Test Leads

The new style test leads that come with the Fluke model 87 DMM and are made by Fluke have failed three times.  The failure mode is that ALL the strands of wire fracture in the same plane about 1/8" past the strain relief behind the shrouded banana plugs at the probe end.  This is not a stress type fracture where you can see deformation of the metal, but rather as if the wire had been cut in a shear.  This has happen to me with 3 different sets of test leads.  Each time Fluke was notified not only that there was a failure, but that it was most likely a design or manufacturing defect that caused it.

One of the symptoms of the failure is that the meter reads zero volts when in fact there is voltage in the circuit.  This is a safety issue if the meter is being used to determine if a circuit is hot prior to working on it. 

My guess is that there is some type of work hardening stress (thermal or mechanical) applied to the strands in the manufacturing process and a small amount of flexing of the wire causes a fracture.

30 Nov 2006 - It turns out that the test leads were NOT intended for DMM use.  I have purchased DMM test leads and they do have strain relief on both ends, unlike the above test leads that did not have strain relief on the probe end.  And that's where they failed.

Lap Top Li-Ion Battery

My Sony Vaio PDGA-BPZ52 Lap Top Li-Ion battery has failed.  It's rated at 14.8 volts 4.2 AH.  When connected to the lap top the battery window shows it's model and serial number and says it's been discharged 31 times and has zero charge and that it's being charged.  But after hours no charge accumulates in the battery.

Inside there are 12 cells each rated at 3.7 volts, so 4 cells in series would make the 14.8 volts.  There seems to be 3 plastic cell holders each with 4 cells.  The cells are all interconnected with welded tabs.  Only 5 tabs are connected to the PCB so there's no way that each individual cell is being monitored.  The cells are connected in groups of 3 in parallel. So the left tab is ground, the next tab to the right is 3.7 V (3 cells in parallel), the next tab to the right is 7.4 v (3 parallel + 3 parallel), next tab is 11.1 V and the right hand tab is 14.4 V.

Along the narrow side there's a PCB with over a dozen ICs.
Sony lap top battery
The plastic case can be preyed open without breaking it.  Next step is to unsolder the 5 battery connections from the PCB and check the cells.  When 5.25 volts is applied across any of the groups of 3 parallel cells no current is drawn.  The Li-Ion charging instructions say not to try and charge under these conditions, so it looks like the cells are really dead.  Now to see if replacement cells are available.

Precision Time & Frequency

GPS 1 PPS Stability

The GPS system provides the most precise timing signal for the amateur.  A GPS receiver, like the now obsolete Motorola M12+T (soon to be replaced see the Synergy web site) will provide a 1 PPS output with jitter under 10 ns and this can be reduced either in hardware or software by applying the sawtooth correction to each pulse.

But the jitter can be increased by a couple of orders of magnitude if there is multipath.  In my case living in a canyon with 100+ foot trees surrounding the house I have severe multipath.  The fix was to set the GPS receiver elevation mask to 60 degrees (it was set to maybe 10 or 15 degrees).  This solved that problem.

Installing Coax  Connectors

When installing crimp type coax connectors there are documents that tell you how much outer jacket to cut off, how much shield to cut off and how much insulation to strip off.  But somehow now matter how hard  you try the numbers don't seem to match your connector.  But after you have soldered the center pin in place and you find that you need more or less distance between the pin and the cable shield it can be changed by sliding your hand along the cable while holding it firmly, toward the connector reduces the distance and away from the connector increases the distance.

Also at the start of the assembly process when the furl is put on the cable before beginning, also slip a few inches of shrink tubing that will go over the furl.  At the very end of the assembly push the shrink tube up behind the connector and shrink it.  This provides some strain relief.

Counter Trigger Settings

For about a year (after the above problem was fixed) my data on Cesium standards showed a change in frequency, which should not happen with a Cesium standard, but does happen with crystal and Rubidium standards.  This probably was caused by improper setting of the Time Interval counter triggering.  The correct trigger settings for both 1 PPS inputs and for frequency inputs (1 Mhz, 10 Mhz, etc.) are:

Kitchen Compactor Jam

GE Compactall Trash
      Compactor drive wheel directions
To reduce the volume of recycle items, Al cans since it's hot now (July 2009) I started to use the kitchen compactor for the first time in many many years.  It worked a couple of cycles then jammed with the plunger down.  Removing the four screws attaching it to the counter allowed pulling it out.  Then removing the four top screws gave access to the drive belt, see photo.

Once jammed there was no response when working the switch.  A probable cause is that the can got pushed to one side tripping the container safety switch.  To restore operation the belt was worked off the large gear wheel and while pulling on both sides of the belt the wheel was turned clockwise (from top see photo) thus manually raising the plunger.  Note the threaded rod was well down at the jammed position and comes up as the plunger is raised.  If you're not paying attention  you'll get grease on you hand.

It's now working fine.




Refrigerator Door Shelf Failure

Some time ago there were two failures of the door shelf where is just fell dumping it's contents.  The problem is very thin plastic where the load is concentrated.
Broken
                  Refrigerator Door Shelf
Brass Shim to Fix
                  Broken Refrigerator Door Shelf

Brass shim was on good side of the shelf.
This means that when the refrigerator was cleaned a couple of weeks ago the brass shim fell out and was replaced on the wrong side and the shelf was installed in a precarious way.  A slight nudge, like I did yesterday caused the shelf to fall.  This time I've taped the brass shim so it will not fall out (it was trapped before but no longer).


GE Electric Wall Oven Cold (GE JKP14WOP1WG)


When I was baking bread (Recipes: 5 Minute Bread) the oven was a little cold, but recently a pie came out with the bottom dough raw, not cooked at all.
The temperature sensor was replaced during the bread making attempt to get it working, but had no effect.  Gambling on replacing the controller board does not make sense.
I pulled the oven to measure for a new one to replace the GE model J KP14W0P1WG that was installed when the house was built in the late 1990s.
Once out and on the kitchen floor the element resistances could be easily measured and they both looked OK.  The controller assembly was considered for replacement during the bread baking investigation but there's a no return policy since it needs to be special ordered and it was hundreds of dollars. 

Looking further I could see electrolytic caps on the oven controller and so thought there's a good change that's the problem and at that point changed from working on a replacement to seeing if the old controller could be repaired.  The key to the repair would be using the ESR-Cap meter since there's no schematic or repair documentation for the controler.  Just test all the electrolytic caps and see if any are bad.  Two were.
Cabinet
                  dimensions for old GE J KP14WOP1WG Wall Electric Oven

Hole for New Oven

There are dual 15 Amp breakeers (240 VAC) now in place for the old oven.
The new oven requires a dual 20 Amp breaker setup (240 VAC).
Need to find out what size the wires are and if their ampacity is good for 20 Amps.
If not then repairing the old oven makes more sense.

If the wires are too small to carry the current for the new oven then there's going to be a real problem.
Indoor Breaker Panel Oven Circuit

Wiring for New Oven

There is an outside breaker panel that holds the electric meter and there is this indoor breaker panel.
The upper left two breakers (50 Amp 240 VAC) are for the air conditioner.
The next two below the AC breakers are for the oven.  The breakers are only 15 AMP (probably from the oven spec),
but the wire size is the same as for the 50 Amp AC wiring, so no problem to change to 20 Amp breakers for the new oven.




Existing Dual 20A Oven Breakers

Beakers for New Oven

The old 15 AMP breakers are marked:
 Challenger
Type C215
120/240 V AC
Cu/Al
HACR Type (UL)
Listed Cir Bkr
2 Pole LNJ-554
E7819-S-91 09 04
(SA) LR48907
GE Electric
                  Wall Oven Controler Robertshaw

Can Oven Controller be Repaired by replacing Electrolytic Cap?

The Back element has a resistance of 29.3 Ohms (1965 Watts @ 240 VAC) and the Broil element measures 17.5 Ohms (3291 Watts @ 240 VAC) so they look OK.  Leaving the control board as the most likely problem.

In this photo the release bar has been pulled out, then the flex circuit connecting to the buttons on the front of the oven has been pulled out a little then lifted over the stop pins and is free of the controller.
GE Electric
                  Wall Oven Controler Robertshaw
The label reads:
ER-14500-RP / 100-501-01B / CN: CTL066
SP +/- 3% 163 / 564 / 873 / 350 'F
LO + 10 / HI + 10               RP: 346687
SN: 46258 LBL: 18-167-28 /   GE: WB27K5040


GE Electric
                  Wall Oven Controler Robertshaw
Back side of controller marked: Robertshaw

The slow degradation suggests that the problem is not with the relays, but rather the electrolytic capacitors.

Bending up the tabs holding the relay board and opening the hinge to free the flex cable allows board seperation.
GE Electric
                  Wall Oven Controler Robertshaw

Two Bad Caps

The two boards seperated.
The electrolytic caps upper left to lower right:
ID
V Clbl
Cmeas
ESR
C10
35
470
370
0.46
C8
35
1000
828
0.36
C7
25
47
49.6
4.7
C17
35
4.7
000
---
C1
35
4.7
000
---
It looks like C1 and C17 are bad.
Aluminum Organic Polymer caps are not available in this value so ordered (2 Dec 2011) some low loss electrolytic caps
Mouser p/n: 647-UKL1E4R7KDDANA  100 for $16.50 + shipping.
GE
                  Electric Wall Oven Controler Robertshaw

Bad caps in Analog Temperature Sensing Circuitry

The connector has two white wires and they are from the oven temperature sensor.  The big IC is a LM324N Operational Amplifier.  This end of the circuit board is where the analog DC temperature signal is processed and so is sensitive to leaky or open caps like C1 & C17.  There are also a number of yellow Tantalum caps that need to be checked.  On closer inspection (stronger glasses) the small yellow caps are not Tantalum, i.e. they are not polarized and are just low value ceramic caps so unlikely bad.

The location of the bad caps is consistant with a gradudal degradation in the temperature control.
GE Electric
                  Wall Oven Controler Robertshaw Cap Replacement
                  complete

Bad Caps are way too Small

It turns out that the new caps (4.7 uF 25 V are larger than the factory caps which were rated 4.7 uF 35 volts.  The higher factory voltage rating means that they are way undersized for the combination of capacitance and voltage and so may have been made using the fake electrolyte Wiki: Capacitor plague).

I installed them folded over in case the extra height might cause a clearance problem with the relay board just above this one.
GE Electric
                  Single Wall Oven now works. It used to be very cold.

WORKING! 

The ESR-Cap meter identified C1 & C17 as defective and they were.

I noticed that the thermocouple was reading very high so I stopped the oven and reset the calibration from +35 to +5.  If the thermocouple can "see" the heatintg element then it reads much higher because of radient heating.  Best to have the pizza stone or something in the oven to block radient heating the TC.

The foam is part of the mouse proofing.  I've used a flat blade screwdriver to force steel wool into the cracks and then used the foam to hold it into place.  You don't need the foam if you can jam the steel wool tight, but that didn't work here. 

Note when the oven is at temperature the outside is cold to the touch. (tested on floor prior to reinstalling.
The thermocouple is showing 210 C (410 F) a little hotter than the 400 F set point.

The oven now gets to operating temperature in a few minutes, not the half hour it used to take to get close.

GE Electric Wall Oven Error --F1--  (JKP14WOP1WG)

20 Dec 2013 - Oven beeps and displays --F1--
x
That translates to something worng with the front panel key-panel.
I'm hoping that it just need to have it's ribbon cable reseated a number of times.

Laptop Headset Connectors go Bad

The problem is walking away while wearing the headset.
That puls the cord at right angles to the plug centerline breaking the wires.
Laptop Headset
                  intermittent because of streached wires
The fix it to:
1) replace the 3.5mm stereo Mike Plug.
2) add a short extension cord to the Mike and Earphones.
That way if you walk away the headset will unplug from the extension cord.





Comfort Zone Stand Up Portable Room Heater Squeals and Stops


The first time it was used since last winter this Comfort Zone stand up heater squeals like a banshie with a warble and then the fan stops. Removing the 6 self -tapping screws requires a Philips (+) blade screwdriver and a nut driver type will not work becuase the screws are located inside holes that are too small in diameter to pass the nut driver.

Once opened up a drop from a Radio Shack pocket oiler was applied to both the top and bottom shafts leaving the motor and the fan spun by hand and this was repeated a few times intil the fan spins easily.  Power on and it's running fine.
Comfort Zone
                Stand Up Portable Room Heater Squeals and Stops

Battery Replacement


DiG 9001D hose bib
                irrigation timer Dig 9001D Hose-bib Irrigation Timer
The hose bib timer that feeds the bird bath and 5 gallon bucket would not turn on when the manual on/off button was pushed.  The battery icon was showing an almost dead battery.  After opening the battery cover and seeing that a 9V battery was needed I went back inside and got a new 9V battery before disconnecting the old weak one rather than remove the old battery then go get a new one in the hope that if I minimized the time when no battery was connected I could avoid reprogramming the timer.  After getting the new battery I oriented it like the connected battery so it would just be a un-snap and snap operation.  The switch took just a couple of seconds and the timer came up showing the correct time.

On the bottom row of the LCD, that's blank in the photo at left, is where the low battery icon appeared.


Orbit 62056 - 1 Dial Hose Faucet Timer with Brass Swivel
Orbit 62056
                Hose Bib Irrigation Timer
This is a much easier to use unit than the Dig 9001D shown above. 
1) the large dial allows selecting the function instead of using the small buttons and trying to see the icon that results.
2) the display is much larger and can be easily read without bending over.
3) it uses 2 each AA batteries, which is more amp hours than a 9V battery and allows using the Lithium 1.5V AA if it need to work in freezing temperatures.  But for freeze applications it needs to be wrapped to keep it from freezing.

If you press manual while in AUTO mode it comes up with 10 minutes to go, but that can be changed using the + or - buttons.

Patent 7637475 Solenoid, Orbit Irrigation Products, Dec 29, 2009, - uses a moving permanent magnet latching between two poles so only a pulse of energy is used to change state.

Water Misting

It's July and the outside temperature is in the 100 to 105 degree F range.
By opening the skylight in the upstairs bathroom and a window on the North side of the house on the ground floor air circulates keeping the house about 20 degrees cooler than the outside temp.

To get more cooling I've added a Orbit Flex Cobra Mister (Model # 30360 Home Depot SKU # 968869).

just outside the downstairs window, but in about 15 minutes the garden hose burst.

That was fixed by using a hose repair kit and a Hose thread to Hose thread pressure regulator (similar to Home Depot: Model # R463CB Internet # 100210697 Store SKU # 798282) on the hose bib feeding the mister.

In the evening the inside temp may be higher than the outside temp, then it's time to shut off the mister and open all the windows.

Hoover Upright Vacuum

The vacuum was making a lot of noise and shaking.  Removing the belt had no effect, i.e. there was a problem related to the motor impeller.  A chunk broke off and was still in there being beaten up.
Hoover Upright
                  Vacuum broken Impeller (fan) Click on photo at left to see larger version.
Notice there's a chunk missing from the impeller (they call it a fan).  This was caused by one of the screws that holds a "U" clamp
on the belt side backing out and getting lost.  That allowed the motor assembly to tip and then the impeller hit the casing, or maybe
it just ate something that was too hard.

To remove the impeller clamp the belt end in a vise (the shaft is round - no flat) since this is where the belt rides and turn the fan clockwise, i.e. it's a left handed thread.

While apart other parts were replaced: the lamp, belt, Type-A bag and a new screw for the "U" clamp.  About $18 in parts (Sep 2011).

Door Does Not Latch

Ever since I've been in this house there are a couple of bathroom doors where the latch does not go into the strike plate unless you tug on the door.  Sighting when my eye is at the same elevation as the center of the strike plate shows that the latch tongue is vertically centered on the hole in the latch plate, so the problem is that the door is not moving close enough to the jamb.  The reason may be that a painter allowed paint to form a fillet which is acting to make the jam thicker.

The solution is to scrape out the excess paint (a Swiss Army Knife worked).

Self Closing Hinge Spring Broken

Hager 426-R Door Closer Body R-7189
The spring snapped.  It's been about 21 years.  If used once per day that would be about 21 * 365 = 7,665 door openings.
5/32" hex key needed when new to set tension.

Self Closing Hinge Spring Broken

Aeron Office Chair

I bought this new chair in 2002.  It was made by Herman Miller who manufacture modern furniture including the Eames Chair. The Eames and Barcelona chairs are probably two the most famous furniture designs of all time.  In 2013 The hydraulic cylinder at the base failed and allowed the seat to tip at an angle.  It turns out the Herman Miller has a 12 year warranty on these chairs so today the repairman from Trope Group (formerly BB&T) in Santa Rosa stopped by and installed a new cylinder. 

The repair man used his cell phone to take a photo of the left are that has some cracks and maybe they will send a replacement for it.
That's fantastic customer service!

The old cylinder with a central pin on the base at left.
Sear removed as well as top plastic cover to get access.
Aeron Office
                  Chair Cylinder Replacement
New style cylinder valve is a lever at top.
Aeron Office
                  Chair Cylinder Replacement
The cable-clamp tie-wrap at right on back tension shaft.
Aeron Office
                  Chair Cylinder Replacement
Left Arm Cracks
Aeron Office
                  Chair Arm Cracks



Battery Operated Nose-Ear Trimmer (Harbor Freight 93838)

Battery Operated Nose-Ear Trimmer Harbor Freight 93838

For some time this unit did not have enough power to spin the cutting blades.  In order to get it to work you could partially remove the head and if held just right it might work.
The real solution, not in the instructions, is to put a very small drop of clock oil on the inside of the head were the blades rub.  Now it spins very fast and does not even slow down while cutting.  It may be that some other oil, like sewing machine oil, might work (but I doubt WD-40 would work in the long run because it's really not a lubricant).

Plumbing Stuff

Kohler GP77759 Shower Mixing Valve

In June 2006 I replaced the GP77759 mixing valve because there was a slow leak when the valve was off.  Now, 26 July 2010, the valve will not shut off and the whole house needs to be turned off.  The problem is an O-ring is jumping out of it's seat and not sealing.
Kohler Shower
        mixing valve GP77759 with O-ring out of place.
Restoring the O-ring to the proper place does NOT fix the problem, so I have a second mixing valve on order and will not use the shower after returning the O-ring to it's proper place.  i.e. if the valve is opened it works, but when you try to turn the water off it does not shut off and the O-ring moves.  I installed it with some Lube-Gel and will try it just prior to installing the new valve.

The real problem may be improper installation.  The valve body has threaded connectors for compression fittings, but the installer just stuck copper pipes into the body and soldered them.  This may be overheated a plastic part?

Rather than ordering just the GP77759 cap (rocket ship) shown in the photo above, I changed my order to the 76851 Kit that includes the "rocket ship" and the "binoculars" plus some O-rings to completly rebuild the valve.

The GP77759 valve arrived (it was supposed to be replaced with the 76851 kit).  It's now all plastic, not the brass like the old one.
Kohler GP77759 replacement valve Kohler GP500520
GP77759 Mixing valve (Rocket ship)
GP500520 Balancing Valve (binoculars)

Kohler GP500520 Balancing Valve

The master bath shower stall has two shower heads.  The opposite shower head has a problem that it leaks from the shower head when the tub is filling.  This indicates a bad mixing/balancing (binocular) valve.

Patents

3724480 Pressure Compensated Mixing Valve, (Kohler),
5445181 Mixing Valve, (Kohler), Aug 29 1995, 137/98 ; 251/85; 251/86

Kohler Sink Valve Backwards

Kohler Sink Valve The hot valve (on the left) is shown as it should appear when off, but is in fact in the full on position (the shutoff below the sink was turned off so it would look correct).

The fix is to pull the hot valve and rotate the core 180 degrees.

Kohler Shower Temperature Hard To Control


Kohler Shower Hard to Control
                Temperature Itturns out this was easy to fix.
The problem was a loose screw holding the knob to the valve.
Using my Swiss Army Knife I removed the screw cover and tightened the screw.

Leak in Sunpentown SB-2025L Fitting

The washer that came with the washing toilet seat does not seal the joint between the house valve and the T fitting.
Leak in Sunpentown
        SB-2015L fitting

Toilet Tank Crack

Another leak was caused by a hairline crack in the ceramic toilet tank.  Rather than replace the tank (or toilet) which is an expensive item, I'm trying to use Silicon rubber to patch it from the inside.  You can see the crack on the top edge of the tank just above the center of the flush handle.  Photo taken after the first coat of Silicon rubber has cured overnight.  A second coat is being applied and again left to dry overnight.
Toilet Tank
        hairline crack repair attempt

Leaking Flap Valves

It turns out the the tank with the crack also has a leaking flap (drain) valve.  The leak check method that I've heard involves putting food coloring into the tank and then seeing if it shows up in the bowl.  That method does not work on black toilets.  A simpler method is to just turn of the valve at the wall and check the next day to see if the water level has gone down.  The closed valve method showed that I've got two toilets that have leaking flap valves.  The first attempt was to buy a black rubber replacement valve that did not have the float.  It turns out that the open link chain was too short to reach the handle lever inside the tank.  Another replacement flap came with the float and it's chain was the correct length.

x
x
The rubber gasket is green and lumpy.  The seat has no gasket and should be smooth, but has green deposits that need to be removed using a kitches plastic scrubbing pad.
Bottom of tank showing bottom of flap valve assembly.
ottom of
                tank showing bottom of flap valve assembly.
Replacing the flap valve did not fix one of the toilets, so the whole flap valve assembly needed to be replaced.  The gasket that shold seal the assembly to the tank can be seen to be less than optimal, and probably the source of the leak between the tank and bowl.  Will know in a hour or so.
Old Toilet
                Flap Valve Assembly showing poor gasket


Outside Irrigation valves

These have failed 3 times in 12 years.  They fail leaking when there is no power to turn them on.  In two cases the leak was to the outside of the valve and the water showed up in the valve box.  These are what would be called slow leaks.  In the other cast the valve failed as an open even though no power was applied and the water came out the normal irrigation locations.  This is what would be called a fast leak (especially when there was a break in the 1/2" tubing).
Back Irrigation box valves
Back Irrigation box valves

Position No. 1 was not used.  There have been two leaks, one through a valve and one to the outside of a valve.
Side Irrigation box valves
Side Irrigation box valves

Valve No. 3 failed and was removed and the supply line capped.
The best solution will be to remove the box and all the valves along with the manifiold and replace the complete manifold assembly with one using a better brand of valve.

Hydro Swirl 96K6 Pump

A decade or so ago the pump died and I replaced it.
In the past week (July 2012) there have been some flakes of rubber in the tub and on two occasions the pump has stopped and would not start again.  But did start later, like there was a thermal switch shutdown.  My guess is that a seal is going bad adding load and overheating the pump.  If I can get a new pump in time then I'll look into replacing the bad seal and keep this pump as a backup for when the new one has a problem.

PS there are two windows with a great view of the forest.  It's common to see squirrels, birds, stars, the moon or planets.  VERY relaxing.

The Genini Plus II pump used in the Hydro Swirl is probably also used in a number of water pumping applications like outdoor hot tubs, spas, Jacuzzi type bathtub, etc.  It's much more economical to replace the pump impeller and seals than replace the complete motor-pump-air switch assembly.

Hydro swirl 96K6 Jacuzzi Bath
Hydro
                    swirl 96K6 Jacuzzi Bath
The toilet room is just to the left of this photo and
there's a trap door that provides access to the pump.
Jacuzzi Bath Pump
Hydro Swirl
                    96K6 Pump
Looking into the trap door at the pump.
Label on top:
ITT Industries
spec: 0034F00C
model: NR2A-C
3/4 HP, 120 V, 8.5 Amp
Label:
Model: 426009
Number: 52707
Date of Manf: 8/23/91
Hydro Swirl Hydromassage Bathtub Model:
                  426009
Pump Rebuild Kit
Hydro
                    Swirl Pump Rebuild Kit
Impeller for Gemini 4647100 Pump (on right) ITT 4647100
                                                                      35-109-1300
Pump Seal Kit Genini Plus II:
ITT 6000600
ITT 6001531
ITT 6001601
(O-ring: O-028B70)
Pump after cleaning
Hydro
                    Swirl Pump
At the center of the motor end there's a hole
over the end of the motor shaft to give access to the screwdriver
slot needed to hold the shaft while unscrewing the impeller.

After removing the pump nose, as shown in the photo
at the left, a flat blade (-) screwdriver can be used to keep
the motor shaft from turning as the impeller is unscrewed
like a light bulb. 
Pump with impeller removed & motor seal installed.
Genini Plus II Pump w/o Impeller
I pulled on the motor seal but it separated leaving the
metal cup part on the motor and the spring and seal
came off.  So I used pliers on the nose of the metal cap
to pull it out along with the O-ring.

Stack showing the relative positions of the impeller, impeller seal,
motor seal and O-ring.
Genini Plus II Pump Impeller, Impeller seal,
                    Motor Seal and O-ring positions
Now the pump will run for a full 30 minutes (maximum timer setting) without problems and it seems to be running faster.

Refrigerator Water Filter: PUR 4396508 Whirlpool 

PUR 4396508 Whirlpool Refrigerator Water
                    Filter PUR 4396508 Whirlpool Refrigerator Water
                    Filter

Before changing the filter it took 21 seconds to fill a measuring cup with 2 cups of water.
After the new filter was installed it took 17 seconds.
Looks like it's carbon only.

SB-2025 Magic Clean Washing Toilet Seat Mother Board

For the past few times the maids have cleaned the GFI that protects the downstairs bathroom has tripped. I think this is related to the failure of the mother board in the SB-2025 washing toilet seat.  After their last visit resetting the GFI did not restore power (all the LEDs were off) to the seat.
Replacing the mother board fixed the problem.

To remove:

* unplug electrical cord
* press button at back and slide seat off mounting plate
* remove seat and set on floor near by
*remove 2 + screws at back
*remove 1 + screw under control are
* press in the latches (see Fig 3 below) to ease out the bottom plate
* Note: there is a white connector that has not cable attached
* remove 15 cables from the mother board (note they are color and size coded)
* remove 4 + screws and remove old mother board.
** reverse the above steps

Fig 1 the new mother board  K3-N   V2.1
SB-2025 Magic
                    Clean Washing Toilet Seat Mother Board
Fig 2 SB-2025
SB-2025 Magic Clean Washing Toilet Seat Mother
                  Board
Fig 3 Inside the SB-2025 (lataches along front edge)
SB-2025 Magic
                    Clean Washing Toilet Seat Mother Board
Fig 4 the old mother board K3  V1.6
SB-2025 Magic
                    Clean Washing Toilet Seat Mother Board


Electrical Wiring

Circuit Breakers 

A Square-D XO Dual 50 Amp breaker failed to power an air conditioner.  Sometimes cycling the toggle on and off would restore the circuit.
The problem turned out to be that one of the Platinum contacts was disconnected from the conductor.

Do not manually turn off these XO series breakers.  Doing so may destroy the breaker.
This may be because of age or the design of the XO series breakers.


Both contacts are in place on this side
Square-D XO Dual 50 Amp breaker failed
The bottom contact is laying on the center divider.
Square-D XO
                  Dual 50 Amp breaker failed


Power Line Cords

IEC

 U.S. Plug shown for Modern IEC A.C. line cord
IEC Plug
IEC Socket

PH-104 Normal

there was a different cord end (Belden 7A125)  that went into the equipment as shown below:
This is called a PH-104 and is made by Volex and can be ordered from Mouser.  There are two versions the standard and reversed.  In the reversed version the hot and neutral wires are reversed from the normal configuration going to the instrument.  The plug shown is marked "Belden 7A-125V" and it's cord is marked " 18-3 TYPE SVT E-3462 LL-7874"  I don't know if this one is standard or reversed?
I think the stock cord was HP p/n 8120-0078
PH-104
                Plug
PH-104 Socket

PH-104Reversed


U.S. Standard Wall Outlet

NEMA 5-15
120 VAC   15 Amp max
U.S.
                Standard Wall Outlet NEMA 5-15 120 VAC 15 Amp max

Voltage Measurements

Neutral - Hot = 123.3 VAC
Ground - Hot = 124.3 VAC
Neutral - Ground = 0.64 VAC
McMaster-Carr
                  p/n 1447K13 International Business-Machine Power Cord
240 VAC International plug to standard IEC socket cord.  For more see the HP 4395 Frequecy Converter into.

Links

Design News - Made by Monkeys
UK Hints & Tips: first page, second page, Repair Brief 1, Repair Brief 2, Repair Brief 3,
Sci.Electronics.Repair FAQ - includng using a scope with a 50 Ohm terminaltion and a square wave signal generator as an electrolitic cap ESR Scope.

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