So,
Will read recommended repair manual tonight, so forgive anything that may overlap. Also, it's really annoying that a lot of these manuals are password protected, allowing print only. I have a great OCR program that would be awesome to make these searchable. Oh well
Have another scope on the way, but it's probably wasted too. lol I'm a glutton for punishment. I have 10 8640B's waiting in line, that need functional checks and gone through.
With the Vreg ruled out for the most part, it's output seems to be stable, I focused on where the +15 was coming from before it reaches the J119 header.
It looks like the DLY REF 1 headed from U2521 through U2620 (High Speed OpAmp).
This is the schematic I'm working with:
A quick check of supporting components in the path turned up a bad resistor, R2720. Bottom of the red circle. I replaced that, and things have improved. It still freaks out, just not as bad and it takes a bit longer. Even a blind squirrel gets a nut once in a while.
However, the sound is definitely coming from the back of the crt, so maybe all of this is moot, if that's garbage. Maybe a problem with HV side of things?
Again, any suggestions are welcome.
Lawrence