[R-390] need help with R-390A symptom

[Bob Young]

A little background on this radio, this was my first R-390A and I had Chuck Ripple restore it and he did a beautiful job so that's probably all I have to say about that. Whatever is going in it has been a gradual thing, it's more of an annoyance than anything and yes the lower volume no hum condition is the correct one as I'm sure you all know. I haven't had it apart lately will probably try to trace it with a scope, the BFO now needs adjusting also, little minor thing, I've used it a real lot over the past three or so years. I am going to check all the tubes though and poke around the wiring harnesses although I don't think it is a loose wire or anything like that. I think some componant is shorting and/or shorting to ground perhaps. I'll report back when I have some time.

Bob Young
KB1OKL

> Message: 5
> Date: Thu, 8 Jan 2009 18:08:42 -0800 (PST)
> From: Joe Foley <redmenaced at yahoo.com>

> 
> Hmm, not knowing how long you've had this radio, it could be new to you, or what kind of work you've done on it so far, I will guess that one of the first things that should be done is to clean it thoroughly and tighten all of the ground connections looking carefully for any sign of corrosion.  That would be all of the tube socket bolts, too.
> 
> Next would be to test all of the tubes properly, that means to do the "shorts" test while tapping the crap out of the tube with your fingertip or the little rubber hammer that was meant for such.  Wearing the headset that can be used with the TV-# series testers will help to show any problem tubes.  Also, leave the tube in the tester to heat up before testing.  Yes, it takes forever.
> 
> Then, if you still haven't found "A" problem, or not "THE" problem, turn the radio on its' end and with the covers off use a variety of wooden sticks of different shapes and sizes to poke around at the wiring harness, the connectors, and anything else that looks suspicious just to see if anything makes noise.
> 
> Check tube pins and sockets for corrosion and looseness, check tube pins for straightness.
> 
> Report back with anything you find,
> 
> Joe
> 
> 
> 
> 
> --- On Thu, 1/8/09, Bob Young <youngbob53 at msn.com> wrote:
> 
> > From: Bob Young <youngbob53 at msn.com>
> > Subject: [R-390] need help with R-390A symptom
> > To: "r-390" <r-390 at mailman.qth.net>
> > Date: Thursday, January 8, 2009, 2:33 AM
> > After my radio been on for perhaps 10 minutes, the volume
> > will instantly increase along with some hum to where you can
> > still hear it with the volume on 0, this happens suddenly
> > almost like a bad connection just got straightened out
> > excpet for the hum. Something as simple as switch from one
> > antenna to another will make the radio go back to normal.
> > Also turning it from on to standby and back again always
> > straightens it out. The AGC seems to work fine. I had
> > suspected maybe a partially burned antenna radio relay at
> > first but don't think it could be that. It will do this
> > off and on for a while and sometimes after several hours it
> > seems run normally for a while. Any ideas on where I should
> > begin to look?
> > 
> > Bob Young
> > Analog, MA
> > KB1OKL
> > *******

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