Al:
Yessir! I did dump the EPROMs. The contents look good. There are ASCII strings in the
first three, the forth one has nothing readable, I hope that's because its all code. Hard to know.
Let me know where you would like them sent.
When my attention turns to the non-prime board, which is very different from my prime board,
I'll get those ROMs too.
Chuck:
The original caps were in fact not clearly marked, but the board was.
You can see an orignal board (above) compared with my recap, lower.
See my dwarf caps in the upper left of the lower board.
https://i.imgur.com/FRlVP8R.jpg
There were + marks on the board.
I made some progress. The flyback is located on its own module.
On both machines, the flyback diode was practically dust. The cap there was
broken on the parts machine. I replace the diode with a beefy one I had handy-
may not be the best/right specs but I figured it would be OK for starters.
https://i.imgur.com/wo6NvkL.jpg
I am looking for similar flyback design to get a diode part number off of.
(Cause I don't have the maintenance manual to know the right one!)
The module on the parts machine also had a capacitor with one leg detached.
Clearly these components get some abuse.
So after recapping the video board, the flyback module and replacing that diode,
I now have high voltage generation. I could hear it. But I heard two SNAPS that I could
not locate the source of. Unfortunately I was not right over the unit to get a sense of it.
I *think* it was from the video board.
I powered down, looked around, and next power up, no snaps.
I guess I blew something but noting looks fried.
There was never any image or beam on the CRT.
I discharged the tube to continue diagnosing, and it was definitely charged- SNAP!
That's progress but I really hoped it was going to work this time, now I have to dig
deeper into measurements I don't know how to do. yet.
When I got the board out, I noticed the transistor with the heatsink in the lower left was warm,
the similar one on the upper right was cold. Cold that might mean that part of the circuit isn't doing
anything?
QUESTION: If I have HV being generated, what can I assume in the path is good?
I have to admit, out of the transistors on the board, I can't say I definitely know which
one is the HOT.