[Heathkit] Screen bypass caps (was DX-100B on Phone - bad audio distortion /oscillation)

[Rick Poole]

Any particular reason those 0.0013-uf screen bypass caps in the 
DX-100 finals aren't something more common like 0.001?  I mean, it's 
not like they have to resonate with anything.

Oh, by the way, all you guys that told me to replace the screen 
bypass caps... just discovered that one of the screen bypass caps 
wasn't even soldered on the ground end.  It looks like it has been 
like that since the day it was first assembled, 50+ years ago.

I am closing in on the problem.  I backed out of the SB-10 mod and 
now when I put my scope probe on the wire running from the output of 
the driver to the grids of the finals, the problem seems to go 
away.  There's a 47-pf mica cap between the grids and ground and I am 
replacing that.  But, I thought micas were supposed to be safe from 
"old capacitor disease".

Rick WA1RKT