Collins R-392?

[majoco]

So turn the knobs to a frequency where you know there is some action with a longer piece of wire for the antenna then sit and wait. Try 6055kHz about 0500z.

 

[mfn002]

I did check the strongest stations around here this morning (7555 and 11550 WEWN, 9570 and 9580 Radio Australia, as well as most of Radio Habana). I didn't hear anything but static, although I could have sworn during a frequency sweep that I heard a faint voice somewhere in the 6 MHz band.

 

[W2NJS]

This is odd...
I decided to remove both side panels and pulled out every tube to see if any were burnt out (I didn't see any). I put them back in, reassembled the radio, and turned it back on. Lo and behold, there was a burst of static every time I touched the antenna. Now, I notice that the static tone and pitch change every time I change the MHz band. Unfortunately, I have yet to hear a single voice.

Also, during my inspection, I discovered that all of the tubes were from different manufacturers, so at some point someone had replaced the original ones.

Yes, a tube can be bad even with the filament glowing. The filament is used to heat a metal (usually thorium) that emits electrons, and with age the number of electrons emitted by the tube declines, in which case the tube is termed to be "weak" and is replaced. That's why tubes get replaced. In addition, there are many capacitors in the radio which gradually fail with age, so even if all you tubes are okay those caps can be the major cause of the radio's poor or non-existent operation. Less likely a cause is burned out resistors, which you should also look for, primarily with a visual inspection but also, when you have time to dig into things, with a resistance check on each one. To do a decent job on a receiver you need a signal generator that you use to inject RF signals at different points in the receiver's circuitry, and doing that will enable you to isolate electronic receiver sections that are not working or are otherwise out of spec.

 

[mfn002]

This is rapidly getting above my level of expertise, considering that I am new to the world of vacuum-tube electronics.

 

[W3DMV]

The radio will work on 24-28 volts. I had six of these receivers in my shack in Viet Nam... I ran mine on
2 -12 volt truck batteries in series (24v), and charged the batteries with a generator as needed. Performance is excellant when everything is working... This receiver is a mechanical marvel. More gears
and shafts than a slot machine ! Good luck

 

[k9rzz]

This is rapidly getting above my level of expertise, considering that I am new to the world of vacuum-tube electronics.

Think of it this way. It's 40 years old! One ... it's gonna need some TLC. Two ... it's no where as complicated as a current computer.

You can do it. Just take it step by step.

 

[jackj]

Specification

I just thought of something. Depending on which specification I look at, it says the power input is either 24 or 28 volts. Even the manuals seem a little ambiguous as to what the voltage input is, with some pages saying 24 volts and others saying 28. Should it be 28? It just occurred to me because I noticed that my 24 VDC 6.5 amp power supply got very hot when I had the radio on. Although this might have something to do with the problem, in my world, the simplest solution is usually NEVER the actual solution. :roll:

There is no difference between 24 volts and 28 volts, at least where this receiver is concerned. Most Army/Navy electronics used in vehicles ran on the vehicle's electrical system which was 24 volts. They used 2 standard 12 volt batteries in series. The 28 volts listed is for a vehicle electrical system that is being charged. Your car's 12 volt battery will measure 14 volts with the engine running.

 

[mfn002]

I thought so. I was just making sure. Anyway, when I was looking at the tubes yesterday, I noticed that they all had what looked like some sort of date code on them. One I found was marked "3-43". Others were marked "67-4" or something similar. One observation I did make was that there was minimal heat discoloration (blackening) on most of the tubes, so I don't think this unit was used very much.

 

[lep]

Your R-392 does not appear to be a Collins.

Has anyone ever played around with one of these? I just got one yesterday, and would be interested as to what people think of this.

Your own listing of the nameplate data doesn't reference that your R-392 was built by Collin but by some other manufacturer. For military surplus collectors the value is usually much higher for genuine Collins made receivers.

Get a book from a good technical library on the theory of superhetdrodyne receivers. From any good technical libary your can also likely find book(s) on circuit tracing.

If this is to be a learning experience for you fine...if it is an investment in a radio to listen to, it will probably turn out to be more trouble than it is worth.

You are the one with Hands On, readers can offer suggestions but we can't service the radio remotely.
YOU have to do some research and when you have specfic problems, you can pose them here and get some help. But first you have to go back to basic receiver theory get some clues of what you are dealing with.

 

[W2NJS]

Here is the R392 tube list:

R-392 Tubes

Also:

http://www.roveroresearch.org/r392/r392_2.html

 

[pjtnascar]

Okay, deep breath here....My first radio with tubes in it was a Hallicrafters S40A. Five bucks at a flea market and no idea if it worked. I knew absolutely nothing about tube radios. I got it working by replacing the power cord and cleaning it up. Since then, I have recapped the radio and use it occasionally.

My first suggestion is to get an operating manual and a schematic for the radio. Also, go to the local library or online and get a book about anitque radios. My favorite is "The Antique Radio Restoration Guide" by David Johnon. The book seems to make some of the technical parts of radio restoration easier, and the author explains how the receiver works in easy to understand terms. In the meantime, stop whacking the side of the radio and fiddling around with stuff you are unsure of.

Since you're already tinkering with the radio, you may be able to get it to work somewhat if it is not too badly damaged. As you have already noted, removing and reinstalling a tube made a difference. You can carefully remove and reseat each tube a couple of times to clean up the pins.Be carefule because the sockets often get brittle. Sometimes, this will improve the reception or make a radio work. You can also get some TV tuner cleaner at Radio Shack and clean up the potentiometers and tuning knobs, slides, etc. There are loads of guides online that detail some of these simple proceedures. Don't waste your money aimlessly replacing tubes. Find a place to test your tubes. You may have a TV repair shop near you that still has an old tube tester. This is an unlikely scenario though. A better idea is to visit a local ham radio club. There is almost always a guy or two or four who work on tube rigs and they have tube testers. They will help you out for free, and who knows, you may even end up getting your ham license! If your tubes test okay, you have just saved some money. It may work partially after a good cleaning.

While you're playing inside cleaning it up, look for broken wires, loose connections, burned components, capacitors that have leaked or are swollen, etc.Make a note of the damage so youcan fix it later. Again, there is a ton of stuff online for free to help you with this. Take your time, be patient, and before you know it, you will have a radio that will at least receive something. Is it going to be easy? Maybe, but probably not. That's the fun of anique radios. Nothing feels better than looking at something that was essentially dead when you got it, and seeing it come back to life.

 

[mfn002]

I just got a tube tester on eBay. I made a mistake in saying it was manufactured by Collins, which I corrected in another post. Apparently, the fix I got only worked once, and now it's back receiving nothing. This seems to be a fairly consistent problem with this thing. A fix will work once, I'll turn it off for a while, and then when I turn it back on again, the fix stops working. It's extremely clean inside, and all knobs work as they should. The only broken wire I found was to the antenna, which I fixed. I did find a PDF copy of the manual with the schematics, but it's kinda long (270 pages), and I'll have to look through it a little more. All the caps seem okay, with none exhibiting any signs of failure or corrosion. The resistors are also fine, with none being broken or burnt. It seems now that the only problem is the signal reception.

 

[pjtnascar]

The site W2NJS directed you to has some good info including a trouble shooting chart. On that site, there are details on how to substitute tubes within the radio to test different circuits out.There are also some common component failures listed. These are great places to start looking for trouble. Keep us up to date on the progress. If you need tubes or capacitors, resistors, etc., check out antique electronics supply online. That's where I get my stuff. I've done two and half restorations since I found that Hallicrafters. I learned everything from online and the book I mentioned. Once you get the feel for working on the old tube stuff, it becomes very easy. Have fun!

 

[mfn002]

Just out of curiosity, what particular component sections should I be looking at?

 

[pjtnascar]

Check that site. It had some component numbers that often go bad along with symptoms.

 

[mfn002]

Check that site. It had some component numbers that often go bad along with symptoms.

I did. None of the symptoms match what my problem is, which is simply no RX. I was playing around with the tubes when I nudged one (I was doing it with the power on). The static went away and the audio almost completely faded out. I noticed that this happened only when I pushed the metal shield covering it down some. The tube socket is marked "V506" which is listed in the schematics as the "6th IF Stage". I noticed something similar with the Calibrator-Oscilator Subchassis. When I nudged the V701 Multivibrator tube, there was a pop of static. However, when I removed the V703 Harmonic Amplifier and Distorter tube, there was no effect on the static.

 

[K4OM]

It might be muted.
Possibly requiring a jumper (originally from a transmitter relay) to activate receive.

 

[jim202]

On these older radios, the tube pin connections are probably questionable. You could pull one tube at a time with the power off and take a pencil eraser to polish up the pins on the tube for a better connection. Don't over do it and take the plating off.

The other problem that I would expect to see is the large filter caps in the power supply are probably dried out and not working. This would cause a voltage issue and hum on the DC power lines. Could even cause a low voltage problem. A simple poking around with a volt meter can tell you what is going on. Putting the meter in the AC mode and measuring the DC voltage will show you how much ripple or hum it there.

 

[majoco]

The tubes bases seem to have some intermittant contacts. Jim beat me to it, but to repeat his reply......

WITH THE POWER OFF and the power plug disconnected, pull out and replace each tube INDIVIDUALLY a few times. Make sure that the tube is fully inserted and any screening can is securely replaced and fitted into any retaining clips.

Now try for some stations. It seems strange that you get a noise increase with the antenna touched but no stations. What sort of antenna have you connected? Just a long piece of wire, 20 feet or so, should bring in something.

 

[mfn002]

I used a telescopic whip antenna (for testing). The longwire connecting post has had the lead wire broken off and attached to the BNC connector. Therefore, I can only use the BNC connector. I stumbled across an entire tube replacement set for the R-392 on eBay, so I might just replace all of the tubes and see what happens then.

Another thing: When I turn the unit on, the signal meter jumps all the way to the maximum, then drops down again. When it does so, the audio comes on.