[R-390] A hard one ?

[Renee K6FSB]

sounds like the AGC itself is osc, possible mis-wire or so far out of 
adj (  had one with both ), remove the tube in agc circuit, see if still 
persists
Renée

Pete Williams wrote:
> ​Why  do  I  get the  hard ones?  this is  a new  arrival.
>
>
> IF  MODULE....It  goes into   oscillation..
> 1.. all  AGC  caps   changed
> 2... tubes   changed
> 3..  little or  no - AGC.    Can  also  see  + V on  AGC     (  about + 3
> V)  depending on setting  of   RF  gain  and    local  audio..  AGC
> terminals    correct R  to  chassis.
> 4.. Varying   local gain  and  RF  changes  character  of   oscillation as
> heard  on   speaker.
>  Testing  done  in  chassis  and    external on  extension  cable
> 5..   The  if  of   455 kHz  introduced  to  J513  from  sig, gen  and
> output  level  varied      .Carrier  meter   works  but  has  gone
> backwards  when AGC  goes   positive .
> 6...  tube potentials  to  be  checked  but   a   day of   audio
> racket     a wonder  to  behold .
>
>
> Do  I have a problem  ?
>
> Cheers
> Pete  Vk3IZ
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