[R-390] R-390A IF deck caps in T501 or T502

[Jacques Fortin]

Hi Dave,

You need only two 200pF caps to replace the potentially defective ones in a
T502.
The two other caps within are "dogbone" 39pF ceramics.
To replace the mica caps without removing T502, the feasibility depends on
who/when your T502 was made.
I have three R-390A IF decks in all and the oldest ones from Collins and
Motorola had the internal IFs assembly completely coated by a heavy layer of
varnish-like substance which can make the job almost impossible without
breaking everything.
On my third IF deck however (a Capehart) there is no such coating of the
guts of the IF transformers, to the point that the cores became loose in the
assembly and I had to "fix" those with cyanoacrylate glue.
This is from the T502 of the Capehart I removed one of the original 200pF,
in situ, to be able to read what was marked at the surface (CM15E 201G03).
Made by Micamold, btw... hum !
It was not especially easy to do due to the way those caps are installed,
but it was doable, providing you have the right tools...
Being there, I replaced it with a 200pF, 2%, 500V SM that I had in stock.
This is how I know that the 500V ones fit !
Good luck with yours.

73, Jacques, VE2JFE