[R-390] Help! R-390 Meltdown

[Tom M.]

Look at the schematic for any nearby capacitor that if shorted would cook that resistor.

I had the same thing happen on the IF deck.  A bad cap had let all the smoke come out of a resistor.

Tom N5OFF 


--- On Mon, 3/2/09, Rick Popovich <RickP at fndmail.csus.edu> wrote:

> From: Rick Popovich <RickP at fndmail.csus.edu>
> Subject: [R-390] Help! R-390 Meltdown
> To: "'R-390 at mailman.qth.net'" <R-390 at mailman.qth.net>
> Date: Monday, March 2, 2009, 11:17 AM
> Good morning all,
> 
> I'm having a problem that I hope someone out there has
> also encountered and
> can share their knowledge and experience and hopefully the
> fix.
> 
> I have been working on an R-390 that I acquired as a
> "parts rig". It was
> only missing a power supply so I substituted a P/S that I
> had in my pile and
> fired it up just the see what would happen. To my surprise
> it actually
> worked.
> 
> After using it off and on as a test mule it quit working
> and luckily I was
> right around the corner and was able to shut it off as
> smoke started to come
> out of the RF deck. While I had never removed an RF deck
> before I dusted off
> the manual and pulled it out of the receiver.
> Since I saw where the smoke was coming from it was easy to
> spot the failed
> component - it was R 220 which I've traced to part of
> the 3rd IF circuit.
> 
> Assuming it was probably just a resistor that was tired
> & out of tolerance I
> replaced it and put her back together. No sooner did I get
> it back together
> and fire her up when up in smoke she went - same problem.
> 
> I have stated to check voltages etc. and have yet to find
> what is causing
> this. HELP!
> 
> Any experience/insight or solution would be appreciated.
> 
> Tnx, Rick
> 
> rickp at fndmail.csus.edu
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