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Collins R-392?

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#42
Test the tubes before you replace any. Unless the replacement set on eBay is extremely inexpensive, you will be wasting your money. Also, if something else in the circuit is bad, you may blow out new tubes. If you have the schematic, you can check many components. I would try to put the antenna connections back to the original set up.
 

Fast1eddie

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#44
I just have to say that after reading this thread and researching the R392 and R390, I want one! Although the 390/392 were no longer classified when I went through Signal School, those instructoros in the know spoke of them in hushed and revered tones. Got to spend some time with one while at Fort Devens and only wish I had the appreciation for them as I do today. I hope you are able to get the 392 up and running, in the meantime I am going to look around for one.
 

mfn002

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#45
I suspect it is the tubes because it worked (somewhat) okay whent I first got it, and then the audio and reception started fading by the second and third times I had it on, which, from what I have learned here, indicates that some of the tubes might have either gone bad or are going bad. Oh, and another thing: the middle section of the "Oldham Coupler" that connects the kHz control shaft to the VFO is missing. The previous owner repaired this by moving the two remaining sections close enough together that they stick to each other and turn with minimal slipping.
 

af0h

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#46
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.

That's normal in these units.

Also - if it worked fine the first time out and then got worse the 2nd and 3rd time you used it, my bet would be coupling capacitors. If it's been sitting a while and you hit it with full power and kept it on for a while the first time, then it's even more of a possibility.

Since it's DC you can't bring it up on a variac, and bringing up the voltage slowly can't be achieved properly. The best option then is several short power-on intervals (on/off, wait a minute or so, then on/off again, keeping it on a little longer each time).

Of course it's too late for that now, but for future reference. Coupling Caps seem more likely now the more I think about it, as the AF section works if you do hear static crunches or pops when moving dials and switches.

Speaking of which, don't overlook dirty switch contacts. That alone will keep one from receiving properly as well... Luckily, the design of the switches in those units make them almost self-cleaning. Simply flipping the switches back and forth can sometimes help too.
 
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mfn002

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#47
Where would these coupling capacitors be located? I don't see any mention of such in the manual. Also, the AF section doesn't appear to have any capacitors. The only mention of caps I could find was in the (sealed) VFO and in the Calibration-Oscillator Subchassis. In fact, capacitors aren't even mentioned in the index. Also, after about 2 minutes or so of being on, the switch noise will go away.
When I first turned it on, I didn't actually pick up anything, just static which seemed to change in pattern every time I moved up or down 1 MHz. The audio does work, the volume just got lower, even when at full max. However, the audio starts working fine when I turn on the BFO. The last time I turned it on with the BFO operating, I did hear something, though very faint.
 
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mfn002

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#48
This is interesting...

I turned it on and was playing around with it with the BFO on about an hour or so ago, and heard a loud whining sound. I turned off the BFO, and heard a faint voice. However, signal would appear only after I moved the kHz control around a few times. Yesterday, I swapped around some of the tubes, so I don't know if I moved a failed tube or the process of moving the tubes around rubbed some of the contacts clean (all pins on the tubes appeared to be very clean, however).
 
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lep

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#49
I just have to say that after reading this thread and researching the R392 and R390, I want one! Although the 390/392 were no longer classified when I went through Signal School, those instructoros in the know spoke of them in hushed and revered tones. Got to spend some time with one while at Fort Devens and only wish I had the appreciation for them as I do today. I hope you are able to get the 392 up and running, in the meantime I am going to look around for one.
Hmm- I was an ASA officer when I went to school at Ft Devens and I don't remember the R-390 ever being an item of classified equipment. What we DID with them was often classified but not the actual receiver.

You can often find them in the flea market at large amateur radio gatherings such as the annual one in Dayton (Trotwood) Ohio. The ones actually made by Collins (compared to another vendor) often command higher prices from collectors of military surplus stuff. They still work well if maintaned but, despite the aura, they are a 50 year old design and will not perform as well as current equipement with DSP capabilities.
 

mfn002

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#50
This stupid thing seems to throw me trough a loop every time I think I got it working...

Apparently, it STILL isn't receiving ANYTHING, but I did notice that the background hiss occassionally turned into static. I even tuned it to a local AM station and got nothing.
 

mfn002

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#51
This morning, I tried once again to see if I could pull anything out of this radio. Not surprisingly, I got nothing. I am getting my tube tester tomorrow, so I'll probably have a better idea of what's going on then. I sure as heck hope I didn't throw away $332 on a radio that's beyond repair.
 

kilokat7

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#53
Well, I think I found the problem. These are all the dead tubes:
(These tubes are from almost every section of the radio)
Please define "dead". Low emission, open filaments, or? I only ask since it seems odd to me that so many tubes would be found bad. Not that it isn't possible, just seems strange to me, kinda like this whole thread.
 

mfn002

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#55
I couldn't tell exactly what was wrong with them, all I know is that my tube tester said they were either weak or bad. I used a Seco GCT Grid Circuit Tube Tester. Since this is the first time I have ever used a tube tester, I'm not sure exactly how reliable that is. Just to be safe, I ordered a replacement tube set.

UPDATE: I checked the tubes again, and this time most of them are fine, but a few are showing to be weak. I put them back in, but now the audio's REALLY weak (almost inaudible--even at max volume).
 
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#56
That tube tester looks to be a simple conduction, or cathode emission, tester. Sort of like the old 'drugstore tube testers' of the 1950's and 60's. I didn't spend a lot of time looking around on the Internet so I don't know how you program the tube tester to test different tubes. It doesn't look like there are enough switches to fully set up the socket pins for all the different tube types. Tubes come in all different configurations, diodes, triodes, pentodes, power pentodes, etc. Also there are many combinations of those types, dual triodes, a triode and two diodes, a triode and a pentode and many others. The socket pins are hooked to different tube elements, only a few tube types have the exact same pin outs. I don't know how many different tube types there are but I used to have a RCA Tube Manual that listed all of the general purpose tubes manufactured by RCA. It listed, for the most part, one tube per page and had around 250 pages with tube info on them. So you see, if your tube tester can't be setup for all of the different combinations of pin outs, it can't really test your tubes.
 

mfn002

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#58
It's actually the GCT-5. Anyway, with what little the tester told me, I suspect that my primary problem with this thing is probably the tubes; there are most likely a couple weak ones in there.
AF0H, all of the capacitors are in areas that are very difficult for me to access, so I couldn't tell you if they have leaked or not.
Now that I think about it, there might be a loose connection somewhere deep inside this radio. It might explain why jarring it sometimes causes something to happen. I tugged on all of the wiring harnesses, and didn't feel any loose wires, but that probably doesn't mean very much.
God, I wish I could figure out what's wrong with this thing before I get fed up and consign it to the scrap heap...
 
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#59
Dude, have some patience. I thought this thing was a freebie, but you paid money for it? Anyway, don't get frustrated. Your tube tester may be crap. I agree that many bad tubes is unlikely. You would be much better off spending money on replacement capacitors than on tubes in my experience. I have restored 2 radios and fiddled with probably a dozen others and I think I had to replace a couple of tubes and that radio was from the 30's. Troubleshoot one stage at a time. Rome wasn't built in a day. You'll get it, but you gotta be patient. Go over all the simple stuff first, and make notes of everything.
 
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#60
Dude, have some patience. I thought this thing was a freebie, but you paid money for it? Anyway, don't get frustrated. Your tube tester may be crap. I agree that many bad tubes is unlikely. You would be much better off spending money on replacement capacitors than on tubes in my experience. I have restored 2 radios and fiddled with probably a dozen others and I think I had to replace a couple of tubes and that radio was from the 30's. Troubleshoot one stage at a time. Rome wasn't built in a day. You'll get it, but you gotta be patient. Go over all the simple stuff first, and make notes of everything.
+8. Especially that many out of different circuits. My boatanchor has 20 tubes total and since I got it in 1988 only ONE tube was weak enough to truly replace, the other 8 I went ahead and replaced-I just wasn't thrilled with the reading but they were passable. I think you should have it recapped. And check with a close eye for flamed resistors too. I was going to do the recap myself but didn't have the nerve-so I found a great radio restorer and for a few hundred bucks I have a total rebuilt radio. Maybe you could go the same route?
 
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