[R-390] Gain drift

[dog]

Thanks for suggestions. This is an EAC 1863 from about 6-67. I got it at 
probably the Vienna or Gaithersburg fest maybe 20 years ago. Has all the 
panels, most of the EIRC shields and is in not bad shape except for the 
hole in the front panel and scratches. No mods. I've added a grounded 
plug to it since last post, I was using one of those 3-2 prong adapters 
from an extension cord. Now it's properly plugged in. All the usual 
suspect caps have been replaced in the audio, RF, IF, PS sections. Not 
the 5000pf bypass discs though. Been through it in the past for a major 
tune up and everything worked properly and was in mostly in OK tune, IF 
section and RF both. But I have this drop out issue. Last time the gain 
dropped I went through all the tubes in the RF and IF sections to shock 
them to no avail, didn't try the coils. Not sure if it happens in the 
MGC mode but probably, I've switched to MGC and it's still there 
sometimes. I'll monitor the AGC voltage as said. I'm monitoring the 
audio out of the diode load to get rid of the audio sections, so it's 
not in the audio sections. It's almost like even static or any signal 
will get rid of the attenuation where ever it's happening in an instant, 
but shocking things does not seem to make any difference. It seems to 
work fine with an antenna hooked up. AGC system works properly. Gain is 
fine, 10DB S/N is less than 2uV. I can't measure it when the gain drops, 
it always comes back. Also seems like once it warms up for an hour or 
so, no problems.