[R-390] R390a Audio Amplifier

[Craig Heaton]

To All,

Been following this thread with interest. I have a Amelco with the loud
volume issue, can't turn it down. Doesn't seem to be effecting the AGC, yet.
But have swapped IF & AF decks from a Motorola with no difference. Even
traced all the wiring cables looking for grounds, etc.

Leads me to believe the issue is in the RF deck. Just too lazy so far to
remove the RF deck for a lookie see.

Craig,
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-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Norman Ryan
Sent: Tuesday, May 28, 2013 8:29 AM
To: r390 reflector; Steve Hobensack
Subject: Re: [R-390] R390a Audio Amplifier

Hi, Steve,

This is interesting.  I have an R-390A with the same issue which I assumed
was due to a faulty volume control potentiometer.  Now I'm curious to see if
swapping the audio deck with a working spare will eliminate the problem
which would tend to confirm your diagnosis of a failed screen grid cap.

73 de Norman, KG4SWM


--- On Tue, 5/28/13, Steve Hobensack <stevehobensack at hotmail.com> wrote:

> From: Steve Hobensack <stevehobensack at hotmail.com>
> Subject: Re: [R-390] R390a Audio Amplifier
> To: "r390 reflector" <r-390 at mailman.qth.net>
> Date: Tuesday, May 28, 2013, 9:27 AM
> The audio from the Local gain
> circuitry can couple itself over to the Line gain circuitry via the 
> 6ak6 screens (and vice versa) should the screen bypass cap fail. This 
> happened to me. The local gain would not minimize unless I turned the 
> line gain to minimum. As I remember,  one of the plug-in electrolytics 
> was the culprit.
> 
> Steve N8YE
>     
>         
>           
>   
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