[R-390] AGC problems - need help interpreting IF resistance readings

[Dennis Wade]

Spent some time today checking resistance values on the AGC line in
the IF deck.  Definite problem on the AGC bus.

Where the AGC bus comes into each of the controlled stages in the IF deck:

        V501 grid Pin 1 110K, should be 500 K

         V502 grid pin 1 70K should be 500K

         V503 grid pin 1 110K should be 500K

   Obviously something is leaking badly...I checked C512 (bypassing
the agc line in the grid circuit of V502) thinking since that's the
stage with the lowest resistance, that would be the problem.  But, you
guessed it..C512 is fine.  I lifted the ground end and the agc line
resistance to ground didn't change.

      Just for kicks, I put the ohmeter across C502 and C519 (agc line
bypasses in V501 and V503 stages), and didn't see anything but the
110K to ground.   Was that a useful test, or do I need to actually
lift one end of those guys and check for sure.

      What else should I be looking at in the IF deck that could be
loading down the AGC line??

       I running out of ideas..what am I overlooking?

           Thanks

                Dennis
-- 
Dennis L. Wade
KG6ZI
Carmichael, CA