[Boatanchors] Gonset G-76 question and status report

[Carl]

Sounds like a parasitic or neutralization problem due to something 
changing value or leaking. Id start with the bias supply since the final 
should be biased beyond cutoff at unkey.

The manual is on BAMA.

Carl
KM1H

----- Original Message ----- 
From: "Jack Antonio" <scr287 at sbcglobal.net>
To: <boatanchors at mailman.qth.net>
Sent: Saturday, September 27, 2008 4:40 PM
Subject: [Boatanchors] Gonset G-76 question and status report


> About a month ago, I purchased a G-76 "parts radio".
> When I got it home, I figured that it would be worth it
> to try to get it back to operation.
>
> So here is what I found so far, receiver operation was dead,
> due to an open 100K screen resistor for the 6BZ6 RF amp. Not
> cracked, discolored or burned, just open. Reciever works
> good on 75, a little drifty on 40, no serious listening
> on the other bands yet.
>
> Transmitter turns out to have a few more problems, and
> I'm wondering if these problems are what caused the
> radio to be relagated to a parts unit.
>
> Problem is unstable power output on transmit, with
> arcing in the neutralizing and grid tuning capacitors
> on unkey. Only when warm, for the first few minutes
> after turn on, all seems OK. 80 watts out, PA plate current
> OK. Then after a few minutes, you key it, an unstable
> 50 watts out, and arcing on unkey. I found that the
> PA tuning cap needing replacing, as the rotor had shifted,
> reducing the plate spacing, but replacing that did not
> help matters.
>
> Still doing trouble shooting but I have a few questions.
>
> 1. What is the value of the resistor from the PA screen to
> ground? This radio has the 12AQ5 and 0B2 clamp circuit.
> The radio has a 22K 2W resistor in it now.
>
> 2. What is the value of the grid tuning cap?
> (Some of the values on the schematic I have are a bit fuzzy).
>
> Thanks
>
> Jack Antonio WA7DIA
> scr287 at sbcglobal.net
> _______________________________________________
>