General Radio Sound Measurement Instruments

The 1307 Transistor Oscillator was the lead article in the GR Experimenter for August 1954. They claimed over 100 hours of operation from the three cell Mercury Battery.

1307 Transistor Oscillator & 1552 Sound Level Calibrator	1307 Transistor Oscillator	1307 Transistor Oscillator Battery The battery is held by a matal strap clamp that's difficult to access. Why would they solder in a battery and make it so difficult to change. Ans. It's a Mercuty battery and was expected to be replaced by the factory. The corrosion from the battery locked the Level pot and the two set screws holding the Level knob on the pot shaft. Kroil freed up the pot shaft and one of the pot set secrews. Will need to wait till tomorrow to see of the other set secrw gets free. There are patent numbers on the bottom of the battery: ETAL 2542575 Alkaline Dry Cell, 2712586 ? 2636062 Electrochemical Cell and Self-Venting Enclosure, Mallory 2462998 Primary Cell with Permanganate Depolarizer RE23427 Primary Cell with Permanganate Depolarizer,
Battery Removed	To remove the battery: Remove the two knobs (requires being able to turn them to access the two set screws on each shaft). Remove the screw that between the two knobs. Remove the two nuts on the back of the meter movement. Fold the board out and remove the hex spacer that holds the battery clamp. In the photo at left the top electrical contact is (+), you can see "+" scratched on the back of the front panel. Notice the battery is like a bar bell with ends that are larger in diameter than the center so it can NOT be slipped out.
With the Level pot at max it takes at least 3.4 V (6 ma) of battery to get the meter to read 2V (the calibration value for the 1552-B. With the battery voltage at 9.0 (5 ma) the level pot has plenty of room on both sides of a meter reading of 2V. A 9 Volt battery is a little too big to fit where the old mercury battery was. An A23 battery (12 Volts) is very small. I soldered a red and black wires and confirmed that the polarity was correct. Then folded the wires so the point to the opposite end and applied heat shrink tubing. Soldered into the 1307 without using the bracket since it's way too big and the battery is so light the leads hold it. All's well. First application is to see what's going on with the mike on the Harris RF3200ET.
1552 Sound Level Calibrator	1552 Sound Level Calibrator Cavity

1562-A Sound-Level Calibrator

(not part of suitcase set)
Uses a Wien bridge oscillator (Wiki) (a form of RC oscillator) with an amplitude stablising thermistor. Note: the HP 201 used a lamp as the stablizing element.
Under some conditions the thermistor is not hot enough to be working correctly, hence the "Start" control setting to warm it up & test the battery. If the thermistor is cold popping and crackling sounds will be heard instead of clean tones.

Control End
Shown in 125 Hz position (red background).
Circle to the right is the battery test lamp.
Start/Bat Test - OFF - 2000 - 1000 - 500 - 250 -125 Hz
The frequencies are each twice the next lower one.
Probably not designed for communications, but lab
mike calibration.

General Radio
1562-A Sound-Level Calibrator Control End

Source End
Open end I.D. = 1.053"
Adapter I.D. = 0.939"
knurled screw on side allows opening case &
acts as the ground side of a 1/4" phone jack.

General Radio
1562-A Sound-Level Calibrator Source End

Battery Compartment
Takes 9 V battery with terminal on each end.
NEDA 1600
Eveready 226
UK PP4
CM345 Battery test lamp (6 V @ 60 ma) at lower right.
Voltage at lamp base vs. lamp current:

V	ma
7	43
6	40
5	36
4	31
3	27

With 9 V at battery terminals, switch in START,
lamp voltage is 6.3V caused by R110 (62 Ohm) and
Q105 Vces (0.3V).

General Radio
1562-A Sound-Level Calibrator Battery Compartment

4 each AAA batteries can be used for the battery.
It's only 6 V instead of 9 V and so takes longer for
the thermistor to come up to temperature, but then works
fine.

A problem when testing the Harris RF23200ET mike is
that the lowest two frequencies (125 & 250 Hz) are below
the 300 to 3000 Hz voice band.

Using button cells is not a good idea since the current
this unit draws (a few ma) is way in excess of the max
design current for the button cells so they would have a
very short life.

This gives an advantage to the 1552 in that it can be driven
from an external oscillator, like the HP 33120 Function Gen.

GR 1559 Microphone Calibrator

(not in this set). Manual - I have a book (haven't remembered the title yet, probably related to Sonobuoys or Helmholtz resonators, that talks about the equivalence between a mechanical model and an electrical circuit. That's to say an electrical impedance measurement can be translated into a mechanical circuit diagram. The manual is titled: Microphone Reciprocity Calibrator. The method uses a known volume inside a piezoelectric tube with a microphone at each end.

Conrad Hoffman: The General Radio Corp. 1559-B Microphone Reciprocity Calibrator - (Wiki: Measurement microphone calibration)

3327071 Method of and apparatus for computation particularly suited for microphone absolute calibration, Basil A Bonk, General Radio, 1967-06-20, 381/58; 708/843; 73/1.82; 367/13 - This is the basis of the GR 1559.

Measure Sound

GR 1565-A Sound-Level Meter

GR 1565-A Sound-Level Meter Opened.
Battery clips for a common "C" cell.
The mike can be removed and the -P40 Amplifier installed.

GR 1565-B Sound Level Meter

Calibrate with 1562.

GR 1560-P96 Type 1971-9605 Microphone

Microphone
Type 1971-9605
General Radio Co
Serial No 7111

1560-P96 adapter to 3-pin male A3

Accessories mentioned in manual:

1562 Sound-Level Calibrator (p/n: 1562-9701)
1560-P96 Input socket adapter to Switchcraft Type A3M (p/n: 1560-9696)
1560-P52 Vibration Pickup (p/n: 1560-9652)
1560-P83 Earphone Coupler connects audiometer earphone to SLM.
1560-P73 25' Extension Cable (p/n: 1560-9673).
Adapter Cables:

1560-P77 Micro plug to 3/4" spaced banana plug (GR274) (p/n: 1560-9677)
1560-P78 Micro plug to std. 1/4" phone plug (p/n: 1560-9678)
1560-P79 Micro plug to BNC (p/n: 1560-9679)
1560-P80 Micro plug to std. 1/4" phone jack (p/n: 1560-9680).

Type 1560-9590 Tripod (with 1/4"-20 thread)
1560-9521 Windscreen

GR 1560-P40 X1 or X10 Amplifier

Hi input Z, low noise for 1" Ceramic mikes.
Fig 6-16b pg 101 Noise Meas Handbook
2 Socket End

GR 1560-P40 X1 or X10 Amplifier
XLR 3-Pin end

GR 1560-P52 Vibration Pickup

Has 1/4-20 tapped hole in the center of the back.
Two clearance holes for mounting.

Missing the short cable with XLR connector that would mate with the 1560-P96 adapter.

Accessories

GR 1560-4100 Phantom Battery Power Supply This box was covered with tape residue and was missing a number of screws. The Battery test lamp is a GE 344 and it measures 100 Ohms, seems too high. 10 V 14 ma equates to 714 Ohms hot resistance, the cold resistance will be lower.	GR 1560-4100 Phantom Power Supply w/ Ni-Cad batteries
GR 1560-4100 Phantom Power Supply w/ Ni-Cad batteries	Using a bench power supply set to 65 Volts and current limited to 18 ma, each battery has been soaked for about a day. They each show a charge of slightly more than 12 Volts. When the Battery/Charge switch is on Battery There is 20+ volts on the XLR socket contacts 1 (ground) & 2 (+20.87 V).
Cords AC Stacking Line Cord for GR 1560-4100 Phantom Power Supply	1560-P95 1/4" Phone Plug to Dual Banana Plug Cable for GR 1560-4100 Phantom Power Supply Output
Vibration Pickup to XLR 3-Pin Plug to feed signal to 1560-4100 and receive phantom power from 1560-4100	XLR Extension Cord
Adapters 1560-P98 GR-874 to 2-Pin Audio Adapter	1560-P98 GR-874 to 2-Pin Audio Adapter
1560-P82 Earphone Coupler, Audiometer Calibration Set	GR-874 to Dual Banana Jack adapter Patent No. 2548457 Coaxial Connector for High-Frequency Transmission Lines, GR, Apr 10, 1951, 439/583; 174/21.00R; 174/21.0CA; 174/88.00C
1560-? Stand	1560- Suitcase

Scott Instrument Labs Type 453A ANSI Type S2A Sound Level Meter

References

Patents

Microphone Testing (related to Harris RF3200ET mike/audio input circuit problem)

H413, Microphone Output-level Tester, Navy, Jan 5 1988, 381/58 - defensive patent
4296483 Method and means for measuring geophone parameters, Litton Resources, Oct 20, 1981 367/13; 73/1.85 - related to geophones

Strobotac

Also see References for more on Edgerton and GR strobe lights.

2408764

High-speed flash-photography

, Edgerton Harold E, Oct 8, 1946, 396/171, 362/4, 455/66.1, 250/214.00P, 315/230, 455/500, 250/215
2478907

Flash-producing device

, Edgerton Harold E, Aug 16, 1949, 315/188, 315/354, 315/353, 315/208, 315/230, 315/241.00R, 315/241.00P, 315/238
2877341 Liquid cooled flash-producing apparatus, Edgerton Harold E, Mar 10, 1959, 362/264, 315/241.00R, 313/36, 315/241.00P

2939984

Flash device and method

, Edgerton Harold E, Jun 7, 1960, 313/634, 315/241.00R, 315/237, 313/594, 315/241.00P
2975397

Surface-indicating apparatus,

Edgerton Harold E, Mar 14, 1961, 367/134, 200/61.42, 340/686.6, 367/137, 340/692, 340/984

2983850 Condenser-charging circuit for flashproducing apparatus,

Edgerton Harold E, May 9, 1961, 15/241.00P, 315/241.00R
2996966

Underwater-flash-producing-and-photographing system

Edgerton Harold E, Aug 22, 1961, 396/28, 362/8, 396/387, 396/180, 340/850, 362/10
3033988

Method of and apparatus for the control of electric impulses

Edgerton Harold E, May 8, 1962, 250/205, 250/214.00P, 315/340, 356/215, 330/59, 315/241.00P, 315/151
3065667

Transparency photographic apparatus

Edgerton Harold E, Nov 27, 1962, 355/27, 315/234, 315/227.00R, 315/241.00P, 355/68, 355/36, 355/64, 396/33

General Radio Sound Measurement Instruments

Background

Description

Create Sound

1307 Transistor Oscillator &

1552 Sound Level Calibrator