Got back into it. When it shuts down it is apparently losing voltage from the back board which supplies the 24 volts to the inverter board. There is no voltage to R 1193 when it is down, and that comes directly off the supply except for L 1182.
So the problem is in the back part of the power supply. I have yet to take that apart, err, wait I did have the battery pack out. Access is not that easiest thing in the world but not that hard. I am pretty sure it is all going to be a simple iron power supply with a switch for charging etc. Familiarizing myself with it will be good if I am to put in more advanced cells and modify the charging circuit to match. Hopefully it will just work like a - like a - cellphone, run and charge at the same time. Be "eveready" so to speak.
I also ran the power switch through all its positions and from what I heard the batteries do actually work but with very limited charge life. That means the problem is probably after the switch, so I know what to do now.
For now, I would still really like to get this channel switching issue fixed. It runs long enough for that. At worst the power problem is the power transformer, maybe the other roe will work... ??? If not there are solutions all over the place. it could maybe just be a battery operated scope and run and charge off the wall wart from an older printer. Some of them had some balls. Like 24 volts at 3 amps, that would probably do it.
Unless shutting down becomes a nuisance I plan to concentrate on the channel switching. i have one last check to clear the inverter/convertor circuit and I almost did it. When shut down take a resistance measurement at the DC input to it. It could be shorting out. I'll probably give it one more and take the reading. No matter what I have to set it aside for a short and check out a printer. That is not going to take that long, at the worst it will involve ordering a new print head. But that'll get it off the bench.
The only thermal cutout I see is at the primary of the AC transformer. That means that when I switched it to battery it should have at least had a power light for a second. It did not.
Going back to the other thread now.