Collins 51S-1 fix

[biff44]

can i assume this is an older type of radio? one with ELECTROLYTIC capacitors in it?
maybe you have a wonky capacitor, one that's electrolyte has dried and no longer filters noise, OR one that has some degradation to the aluminum foil layer, and has burst of shot noise popping thru it.

 

[neazoi]

can i assume this is an older type of radio? one with ELECTROLYTIC capacitors in it?
maybe you have a wonky capacitor, one that's electrolyte has dried and no longer filters noise, OR one that has some degradation to the aluminum foil layer, and has burst of shot noise popping thru it.

It is not the main reservoir capacitor, I have already checked that by bypassing it temporarily. The rest of the electrolytics are basically in the bias +b and the VFO does not get any bias, just anode.

I have ordered a set of US-made 7543 tubes to replace two 6au6 that were not original in the radio.
If I am lucky enough, what Brian mentions about a parasitic oscillation, will be shown when I replace the tubes. If not, I will leave the lower voltage mod there and of course the new tubes, that were supposed to be in the radio at first place.