Nice job on that recap! It looks nice and clean, and I really dig the way solid polymer caps look on these boards
Do you have access to a working Classic or Classic II that you could try this motherboard in? It’d be good to rule out the analog board.
No idea about the RAM jumper.
The ink in one of these is oil based and not water based (otherwise, the hardware would be prone to rust -- same with typewriter ribbons). What has happened if a NOS ribbon has dried out is that the oil has evaporated and/or solidified, but in a NOS item the pigment is obviously still present. Theoretically, such a ribbon ought to be able to be "reactivated" by opening up the case and giving the fabric a quick burst of a spray-based oil. The cartridge rollers and any foam etc. could be inspected/renewed at the same time. The goal is not to make anything sopping wet, but just lightly damp. The ribbon ought to barely stain your fingers when touched.
Renewing the ribbon's oil should do the pins in the printhead some good as well, once printing begins.
WD-40 was often used back in the day to breathe extra life into used ribbons, so it should work on NOS ribbons even better. However, WD-40 WILL gum up if left to fester for long periods of time, so beware if using it around a printhead that might, as is in the nature of things in our hobby, lie inactive on a shelf for years between uses. If a proper machine oil (which WD-40 isn't) can be found to use instead, I'd go with it.
I obtained this Classic II a few days ago, and just finished re-capping it. It made a funny picture with no startup sound at all prior to the recap. It still does the same now. There was no battery explosion, just cap goo that I cleaned. It’s possible that there is an eaten trace somewhere, but I can’t see anywhere that is terribly damaged. The traces under the caps looked just fine. I’ll include board photos and how the screen looks. I can’t decide if it is a funky checkerboard pattern or not. In addition, it has two RAM sticks inserted. Also, the RAM jumper is not installed...if I recall, that is done with max RAM, correct?
Thanks. What is and where is located that VRM please ?
The speakers are badly rotten, so I suppose don't working.
There is another led lit when I plug it, green, on the opposite side from the ram slots.
Edit: After a bit of cleaning the speakers, there is a chime !
So I suppose the main board is good ?