[R-390] R392

[Guido Santacana]

Gang,

    I removed the lower subchassis, checked everything. No resistors out of
tolerance and caps OK. For the first time I really went through the solid
state audio mod finding out that it mostly follows Mike Dinolfo's design.
Nothing seemed wrong here either. All tubes were tested and reseated in
their sockets with Deoxit on the pins. Same thing with all connections. The
subchassis was reinstalled and the radio had a run of several hours without
any problems. I will give it another run today before returning it to the
case and if everything is OK then the conclusion is that the noise came
from some bad connection. It could have been induced by heat. The day that
the problem occurred was a specially hot one. From now on I will slide it
out to allow better cooling. Thanks to all of you for your recommendations.
They will go into my notebook where I keep repair notes of all my BAs.

BTW, this is the only BA in the shack that my YL likes!


Best 73s

Guido

Guido Santacana KP4FAR

On Mon, Jun 19, 2017 at 10:44 PM, Barry <n4buq at knology.net> wrote:

> I've never owned one, but by the pictures I see on the internet, the 392
> doesn't have a diode load connection brought to the outside like it's
> bigger cousins.  If there's a similar pickoff point inside, you could feed
> that to an external audio amp and see if the problem persists there.
> Alternatively, you could take the IF output and feed that to a general
> coverage receiver (assuming the IF on the R392 is 455 kHz or some other
> frequency readily receivable on a general coverage radio).
>
> If the problem doesn't persist listening on those alternative paths, then
> the problem is downstream from that point so that might at least narrow it
> down a bit.
>
> 72 and good luck with it,
> Barry - N4BUQ
>
> ----- Original Message -----
> > From: "Guido Santacana" <gsantacanav at gmail.com>
> > To: "Bob kb8tq" <kb8tq at n1k.org>
> > Cc: "r390A" <r-390 at mailman.qth.net>
> > Sent: Monday, June 19, 2017 8:45:04 PM
> > Subject: Re: [R-390] R392
> >
> > The more I hear it, the more it smells to an audio circuit problem. It
> > takes about 5 minutes for the noise to appear after turning on the radio.
> > After reading both Charles and Bob's recommendations sounds like a
> cracked
> > resistor but could be any of the other alternatives. Tomorrow the radio
> > goes on the work bench ( in my case a small mechanics folding bench from
> > PepBoys). I will report my findings. It's been quite a while since my
> last
> > R392 repair.
> >
> > Thanks for the recommendations gentlemen. Highly appreciated.
> >
> > Best 73s
> >
> > Guido
> >
> > Guido Santacana KP4FAR
> > EAC-R390A, Steward Warner-R392
> >
> > On Mon, Jun 19, 2017 at 6:59 AM, Bob kb8tq <kb8tq at n1k.org> wrote:
> >
> > > Hi
> > >
> > > I’d put “60 year old unsoldered connection” on the list along with
> > > “cracked resistor”.
> > > Both are a poke around a bit and listen to what happens sort of thing.
> > >
> > > Bob
> > >
> > >
> > > > On Jun 19, 2017, at 12:12 AM, Charles Steinmetz <
> csteinmetz at yandex.com>
> > > wrote:
> > > >
> > > > Guido wrote:
> > > >
> > > >> There is some popping before it come back
> > > >> so I suspect a bad cap in the audio section.
> > > >
> > > > If the volume control has no effect, the problem would appear to be
> in
> > > the audio section (V606, V607, V608 and associated circuitry).
> > > >
> > > > Bad cap is certainly one possibility, but don't forget the most
> common
> > > source of such problems, namely noisy contact between tube pins and
> their
> > > sockets.  To check, just put your finger on top of each tube (one at a
> > > time) and wiggle it a little.
> > > >
> > > > Best regards,
> > > >
> > > > Charles
> > > >
> > > >
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