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Collins R-392?

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#61
Okay, you're on the right track by focusing on the tubes at this point.

Have patience. You're still thinking that it's "A" problem, but in reality the radio probably has a number of problems that need to be fixed. Just like you're fixing up an old car, just do 'em one at a time and you'll get there!
 
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#66
Michael, since you've gone to lots of trouble

trying to find what's wrong and gotten inside the radio, let me give you some serious safety warning.
Be carefull of the voltage, it hurts to get zapped, (amperage is what kills people, that's a safety thing all by it's self).
WEAR eye protection!!! When you power up a piece of equipment and a cap is shorted, it will possibly explode and fly off in many pieces and can cause eye damage. The same with resistors when a short down ciruit happens.
But that aside, caps will be your most likely bad components, then resistors, tubes and DIRT.

someone mentioned taking notes. THAT is always a good idea, and draw a skitch of how you desoldered a part. (digital cameras come in handy for that part, before removal and so on.
 
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mfn002

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#67
Judging by the fact that I've powered it on dozens of times since I got it, I suspect that any caps that would explode would have by now, but none have. Also, all the caps in this radio are small and usually measure in the micro-farad range. Even if I did find a blown one, it would be almost impossible for me to replace it because the boards they are on are mounted vertically and are mostly soldered into place. Since I didn't smell the odor of burnt resistors (which I have come to know very well over my years of working with electronics), I don't think there are any others in areas I can't access. Hopefully, it is just a defective tube somewhere that's causing the problem. I'm getting the replacement tube set on Monday, and then I'll go from there. If it's anything more than that, I'm pretty much screwed, since my knowledge of this type of stuff is fairly minimal and I've had a terrible time trying to find parts.
 
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#69
Hang on to that can-do attitude and reward yourself with an occasional 807 at the local pub.

You'll get 'er going again!


 
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#72
Gotcha. Waiting for a response.
Michael-if you can, scare up a schematic for those guys like they are requesting-if you read around in there a bit, particularly Edd's posts, you will see the lengths they go to to walk a guy through stuff. Hope you continue with this-kinda rootin for ya here.
 

mfn002

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#73
When I restored and old National NC-173 this is the place I found very useful.

Antique Radio Forums • Index page
Just posted on the forum there (under MIKE511986). I would REALLY, REALLY love for this radio to work again.

Oh, and here's some pics that may help describe some of the problems that I'm talking about.
 

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#74
Okay, so you're working on getting some tubes, in the mean time you can probably test out parts of the receiver. How about the audio amp? Grab some audio from your Ipod, or whatever, and couple it into your final audio stage through a capacitor and see what you get. If you get loud clear music, then you know that section is working.

How do you get at it? Got me! You may have to pull out the board, connect your test lead, and re-assemble.

Does your official manual give any testing procedures?

http://amfone.net/Amforum/index.php?action=printpage;topic=30620.0

http://www.antiqueradios.com/forums/viewtopic.php?t=99865

http://www.r-390a.net/Pearls/R-392.pdf
 
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mfn002

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#77
Okay ... I'll bite.

Why wouldn't it work?

The tube only amplifies 1khz tones?
The manual seems to specifiy that, although, I might want to test that MP3 idea. How would I go about doing that? What kind of cable do I need?

EDIT: I'm bidding on a confirmed working one on eBay right now. It comes complete with the mounting tray, power connector, speaker, and headphones. If I win that one, I probably won't need to worry about this...unless someone wants a screwed up R-392 to play around with. The bidding ends tomorrow, so I'll update this particular part then. In the meantime, I'll keep trying to get this thing to work, even though it's looking increasingly hopeless.
 
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mfn002

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#78
Put in the new tubes this morning. Still the same, although the background hiss is a little louder now, but the squelch and volume controls don't seem to affect it. However, the DB meter needle moves when I adjust the squelch.
 
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#79
Okay, that eliminates that variable. Good. Check!

Really, for the matter of simply testing the audio circuit, it shouldn't matter what kind of audio you put into it. Use whatever audio cable you have handy. Feed it into the audio circuit. You'll have to look at the schematic to pick a spot. Find the audio amp tube, look for the grid of that and pick a spot before there. You'll need to feed the audio through a capacitor to isolate radio voltage from your audio source. Use whatever you've got.

If you get a working unit, then keep the current one as a parts source. Then you'll be good to go!

Keep us updated.
 

mfn002

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#80
Okay, that eliminates that variable. Good. Check!

Really, for the matter of simply testing the audio circuit, it shouldn't matter what kind of audio you put into it. Use whatever audio cable you have handy. Feed it into the audio circuit. You'll have to look at the schematic to pick a spot. Find the audio amp tube, look for the grid of that and pick a spot before there. You'll need to feed the audio through a capacitor to isolate radio voltage from your audio source. Use whatever you've got.

If you get a working unit, then keep the current one as a parts source. Then you'll be good to go!

Keep us updated.
Okay. I know where to put the audio, but what kind of cable do I need?
 
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