MILITARY COLLECTOR GROUP POST, Sept.28/98 Index: TCS TECH TIPS; From Dave Stinson MEMBERS WRITE; PRC-68, -126 Microcontroller? PRT-4 Tone Squelch Compatibility, I QUIT, SEAN's GETTIN OUT; Offering the following gear For Sale HUMOR; *********************************************** TCS TECH TIPS; From Dave Stinson First check every tube in the whole rig. This can be tedious when you really want to get a rig running, but this simple task can save a lot of head-scratching later. Next get some good contact cleaner, light machine oil, light gear grease, some "Q-tips", some old rags, an old toothbrush, a jug of distilled water and a good grade of paste silver polish (yep--that's right). On the receiver-- First thing- don't crank on the switches and knobs until you get them inspected and lubed. The bandswitch is very sturdy but I destroyed a section once by cranking on it before I looked at it. Same with the crystal switch. They can be hard to reach but make the effort. Both those switches go intermittent without cleaning. They will need good contact cleaner and the mechanicals will need oiling and greasing. The back-lash spring split-gear on the receiver tuning cap will need cleaning and lubing as well. Spray the bandswitch and rock it gently, watching the wiper contacts to make sure they move smoothly without binding. I bent one over double because I didn't look first. Look for a bathtub cap mounted on one of the frame legs of the receiver chassis. This one is noted for going open and it will kill your audio out. I highly recommend running the filaments on 12VDC as designed. Less noise. Also, it's a good reason to build the 12 volt supply so you don't have to mess with seperate power for the transmitter relays. On the transmitter-- Same treatment for bamdswitch and other contacts as the receiver. You'll need to burnish all the relay contacts with either a real burnishing tool or brown paper-- nothing abrasive. Then operate them a few times to re-establish a clean oxide conductive coating. Put a very small drop of very light oil on the pivot points of the relays. Now comes the hard part. Trust me on this-- it's work, but you won't regret it. Unsolder the connections to the roller coil and remove it from the rig. Lay-out an old blanket on your bench to keep parts from walking-off. First remove any loose dirt and dust from the coil assembly. What you want to do is disassemble the thing as much as you feel comfortable with and polish all the bits and pieces, including the inside of the roller wheel, with the silver polish. Don't get the polish in the bearings. Rinse the polish off using the distilled water, rags and toothbrush. Once it's clean, put it in the sun to dry well. Don't use a stove. Reassemble and lubricate the roller. All this work will pay-off in easier tuning and less aggreivation. This cleaning is practically manditory in ARC-5 transmitters, by the way. Dirty loading coils cause all kinds of trouble there. Operation: Max reliable keying speed is about 25 WPM. There should be no chirp and very little drift after a couple of hours operation. They were designed to be stable. The rig was not designed for a 50-ohm antenna, but you can tune one with the settings of the ANT. COND. control. For 80 meters and above, set it in SERIES. There isn't enough cap in there for doing this on 160. You'll need to set it in the center (no antennna cap) and use an external 0-200 PF variable cap in series with the coax. Neither of these ways will tune it to 100% design spec, but they'll get close. If you want that last couple of watts, you'll have to use one of Mike Hanz's UNUN unbalanced-to unbalanced 4:1 baluns. It will get you from 12 ohms for which the rig is designed up to the 50-ohm coax, but it will also eat a watt or two in losses. Your call. Don't let anyone tell you that you need to slash-n-burn, chainsaw or otherwise "mod" the audio chain. That's all "hooo-eeee." If you want a rig that sounds like a broadcast transmitter, buy a KW-1 ;-). All you need is a telephone-size carbon mic element and the rig will modulate 100% at normal voice. That's the ONLY "mod" I ever do to any of my military rigs and it works just fine from the ARC-5, TCS, BC-375, ART-13, etc. Hope all this helps. Others will have more and better ideas. GL ES 73 DE Dave Stinson AB5S arc5@ix.netcom.com ed) I can add very little to this as you've covered most of the areas of concern. Roller Inductor, One thing that need be done while the roller inductor is out (and it is a bitch to get it in and out) is to check it's internal contact wire. A wire runs the length of the roller inductor, down it's center. It cannot be seen when still in the radio. It's a common fault of this radio for one or the other end of this wire to have a cold solder connection that will reek havoc on you when trying to load up the transmitter. Fix it while it's out!! Due to the large gage of solid wire used in the transmitters output stages, and the vibration these radios might have been subjected to, bad solder connections are very common in this area. Suitable mics, the TCS uses an unusually high voltage across it's carbon mic. Most radios that use carbon mics, and were primarily designed for operation from a DC power source derive their low mic voltage from the tube heater supply. But the TCS, given that it was conceivable that it might be operated from an AC source, derives it's mic voltage from a tap on the modulation transformer. The resultant voltage drop across the mic element serves other functions in the modulator chain. As a result, these radios are unusually impedance sensitive, and many mics will not handle the higher voltage. While I don't really want to delve into how carbon mics work, here and just now. The rule of thumb when it comes to them is that bigger is better. In the case of the TCS however, with their impedance sensitivity and higher exciting voltage, many mic types will not work properly. It is a very common, and acceptable practice on most military radio's of WW-II>late 50's vintage for us to use the carbon element from a modern telephone handset. In most cases this works very well, but not with the TCS as there is an impedance conflict. Keeping with our rule that bigger is better, many might opt to use a T-17, or the standard Navy equivalent RS-38. But these mics, though they look large and impressive actually have a very small carbon element, with the RS-38 being the worst. They will work, but they may not be to the optimum level you might want. With all the above in mind, the hands down winner for best carbon mic for use on the TCS and any other military radio is the TS-13 or equivalent handset of WW-II vintage. They have the largest carbon mic element of any I've ever seen, and they are the correct impedance. Not to mention the fact that they also have the best PTT switch in existence. Power Supplies. If you are not fortunate enough to own one of the many varied(and heavy) TCS powers supplies. Fear not, for this is one of the easiest radios in existence to fabricate one for. In fact, you wont even need to build it, usually just add some connectors/cables. Just about any power supply used on old tube type business band radio equipment will work. Be it a mobile vibrator or solid state inverter supply, or one intended for base 110vac operation. And they can often be had for the hauling off. Keep your eyes out for an all tube type GE Progress Line or Motorola equivalent desk top base, or mobile transceiver(their the same radio, in the same cabinet, with different power supplies). These power supplies will have all the required voltages with some to spare, and all you'll need do in most cases is to wire it up. It may be necessary on some of the base power supplies to add a bridge rectifier to the normally AC heater supply, but that's about it. Look for those radios that used dual output tubes(usually a pair of 6146's) as these will have a heavier duty power supply. Heavy duty mobiles supplies can be distinguished by either their use of dual vibrators, or in the case of later model type, a solid state inverter design. One of the nice thing about using these power supplies is that once you've found the correct/original supply for your radio, you can modify the old expedient for use with just about any other tube type radio you want. Dennis Starks; MILITARY RADIO COLLECTOR/HISTORIAN military-radio-guy@juno.com *********************************************** MEMBERS WRITE; PRC-68, -126 Microcontroller? Does anyone know which Motorola Microcontroller Magnavox used in the AN/PRC-68A, 68B, 126, and 128 radios? Alan atasker@ix.netcom.com ---------------------------------------------------------------------------------- PRT-4 Tone Squelch Compatibility, Dennis, I'm looking for the maintenance manual for the AN/PRR-9 and most importantly the AN/PRT-4 and 4A. I need the manuals to be able to see the difference between the -4 and the -4A. As you probably know the 4A will break squelch on the PRC-25/77 and the -4 will not. This is a problem if you want to use these radios as a group and not have to leave the squelch off on the PRC-25/77. If anyone has these please advise and I'll be happy to buy them and pay shipping. Thanks, Ed, (Ekirkley@aol.com) ed) the only difference between the PRT-4 and it's latter "A" model is the addition of an IC 150cps tone generator board. A cheep commercial generator board can be had that will allow complete Compatibility of the PRT-4 and just about any other radio you see fit to instal it in. As 150cps is not an industry standard tone, the more common programmable type generator boards will not function with any reliability, so we must stick to the tunable types. These use a multi turn pot for selection/tuning of the desired tone. While these are offered by a number of companies, and the gifted tinkerer cold build one from he's moderately stocked junk box, I particularly like the Model ST-140 offered by Selectone(see below) for about $15.00. It's the size of a postage stamp(or smaller) and not much thicker. So it can be installed in just about anything that comes along. I've used them in the PRC-10, RT-70, -68, SEM-52, and a number of commercial low band HT's and portables. On the other hand, large quantities of PRT-4A's have hit the marked in the last year, and their prices run about $25.00. It may be easier for you to just purchase an "A" model PRT-4, and save the old one for the future when things may not be so good. Selectone Corp. 23278 Bernhardt St. Hayward Ca. 94545 USA orders: 1-800-227-0276 fax: 1-510-887-4011 info: 1-510-887-1950 *********************************************** I QUIT, SEAN's GETTIN OUT; Offering the following gear For Sale Yep, I'm out of the hobby for the duration, thanks to the assholes down at the VA who are putting pressure on me to spend my time other ways than I've been doing. Please take me off the list of Group members. I've sent in a Wants and Trades so the guys can buy my radios if they want. Offering the following gear For Sale: AN/GRC-9 with LS-474 speaker and a power supply from a GRC-9 AN/TRC-77, rough 2 French ER-79A radios, one with all accesories, one missing long antenna HW-7 with matching power supply Delcom 9600 civilian air-band walkie talkie w/ mechanical digital tuning Uniden Grant SSB/CB radio Realistic 1 watt CB walkie talkie with ni-cads and charger Realistic 30 channel scanner (0.4uv sensitivity from 29-54 MHz) with nicads, charger and power supply 3 PRC-6 radios 2 in good shape, 1 rough and minus antenna 2 Heathkit GW-30 walkie-talkies, work but rx sensitivity is 5000 milivolts one-week reserve on all items for members of the group, after that, there going somewhere else. Thanks Sean T. Kelly, *********************************************** HUMOR; I was scared at first. It was very wide, and very long, and it angled straight up. I decided I had to try it once. I slowly and carefully eased myself onto it. It felt weird at first. Then I got used to it. I went up and down, and up and down on it. I was really loving it. Now I ride on escalators all the time. ---------------------------------------------------------------------------------- I took my fingers and slowly, gently stretched it apart. It was so pure and white. I licked it once, twice... I found I couldn't stop. I licked it faster and faster, and harder. I began to scrape my teeth against it. There it was, in my mouth! All sweet and creamy. I was done. I threw away the outsides of my Oreo cookie. --------------------------------------------------------------------------------- I squeezed it gently at first, then a little bit harder. There seemed to be more and more of it. I moved it towards my lips. It was a strange and new sensation for me. I put it in my mouth and moved it around and around with my tongue. The time soon came when I knew I had to spit it out. It was quite an experience the 1st time I tasted toothpaste. ---------------------------------------------------------------------------------- They were both round and firm. There was only the slightest difference between the two d it hard. I used my other hand to grab the other one and twist it hard the other way. Now there's a brighter light bulb in the livingroom. ---------------------------------------------------------------------------------- It was laying limp in my hand. It was very long, kind of thin. I slid it between my fingers until I got to the end of it. I was turning it on. It became firm in my hands, and the end was wet. Then it got very hard and began gushing out of the tip. Then I took the garden hose and watered the bushes. ---------------------------------------------------------------------------------- I knew it could be done. I wanted to try but I didn't know if I could do it. I called my friend. He said he knew how to do it and would teach me. He put his arms around me and started. I watched nervously in the mirror. He finally finished and pulled back slowly. I felt relieved that it was over. I hate neckties. ---------------------------------------------------------------------------------- It looked warm and dark, and juicy and inviting. I wasn't sure just what I wanted to do with it. I carefully pulled it apart with my fingers to look into it better. I knew how great it would be if I just started eating it. But I decided on catsup for my burger. ---------------------------------------------------------------------------------- They were two of the biggest balls I had ever seen! They hung so heavy and low. I tried lifting them gently, but that wasn't enough. They had to be pulled, and I pulled on them very very hard. They finally came. I moved them to a higher spot on the Christmas tree. ---------------------------------------------------------------------------------- And Just What Were You Thinkin' ???? ;) *********************************************** (The preceding was a product of the"Military Collector Group Post", an international email magazine dedicated to the preservation of history and the equipment that made it. Unlimited circulation of this material is authorized so long as the proper credits to the original authors, and publisher or this group are included. For more information conserning this group contact Dennis Starks at, military-radio-guy@juno.com) ***********************************************