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THE AM BULLETIN BOARD => Technical Forum => Topic started by: Joe Connor on February 15, 2012, 04:22:44 PM



Title: Weird R-392 Problem
Post by: Joe Connor on February 15, 2012, 04:22:44 PM
I have an odd problem with my R-392 that I need your help with. This is a pre-existing problem that grew worse last night.

    Previously, when I turned the receiver on, it would sometimes crap out (i.e, the dial lights would go off and the audio would die). If I turned the power supply on and off a few times, the set would generally behave properly. Last night, it stayed dead. When I tried it again this morning, it behaved the same as last night: dead.
 
    When I first got the set, the seller advised me of the problem and suggested it was an issue with the homebrew power supply that came with the set. However, the problem is not the power supply. I hooked up a spare homebrew R-392 power supply and the problem was the same. (The spare power supply goes with a beat-up R-392 that was thrown in with some other radios that I bought).
 
    Here's what I noticed. When the set died, the S meter would go all the way to the right. If I turned the set from On to Standby, the dial lights would come back on and the S meter would move to the left. If I switched it back to the On setting, it would die again and the S meter would go all the way to the right. Back to Standby, the lights would come on and the S meter would go to the left. (Sometimes, in Standby, the lights would go off and then come back on a few second later). I noticed a soft clunking sound when the set dies. It just seems odd to me that the dial lights would come on in Standby mode but immediately die when I switch to On mode.

      Before I try to diagnose the problem, I would appreciate your thoughts because you folks know a lot more about R-392s than I do.


                                                           Joe Connor


Title: Re: Weird R-392 Problem
Post by: KL7OF on February 15, 2012, 08:31:20 PM
Is there a microswitch behind the panel on the function switch?...like the R390?  If that thing gets out of mechanical adjustment the rig won't turn on...I have never been inside an R392....just sayin'


Title: Re: Weird R-392 Problem
Post by: w3jn on February 15, 2012, 10:37:29 PM
Problem in the filament circuit.  You're jarring something (perhaps a bad connection on the power switch) by messing with the stdby/rcv switch.  There is indeed a microswitch for the main power associated with that switch.  The "clunk" is the squelch or ant relay, most likely.

Here's a simplified schematic of the power distribution in the fil and stby circuits



Title: Re: Weird R-392 Problem
Post by: Joe Connor on February 15, 2012, 11:25:56 PM
Thank you, guys, for the advice and the schematic. It sounds like the first step is to take a look at the switch. Is this the same troublesome switch that is found in the R-390As?

I'll report back what I find. It may be a little while because I have an SP-600 on the bench now. (Thankfully, it has original ceramic discs). I got spoiled working on the SP-600. There is some so much high-quality restoration material on line for that one, especially the 2009 Anthology and the Western Historic Radio Museum site.

                                Joe Connor
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands