Been reading old AK threads trying to get any info about this issue.
In this thread an issue is mentioned about the focus pot being in close proximity to the AGC and current from that leaking into the AGC circuit and producing problems.
http://www.videokarma.org/archive/in.../t-128371.html
I did voltage readings on the AGC control pins but didn't see any radically high voltages, just a bit above and below the 60v indicated on the plate of V6B.
I'm thinking it has more to do with the received video sync pulses on V6B, pin 3, which if too strong, is my understanding, will create a negative potential on the plate of V6B. Will get some scope readings today.