The project that I linked provides the connection for a PicoATX to connect to the analog board. I've got one of these in my Mac SE/30 and there's no requirement to desolder anything on the analog board at all to make it all work.
Pending advice from some of the more knowledgeable people around here The Dead Mac Scrolls has a few suggestions for things to look at for no video output.
You should check out their troubleshooting guide https://bluescsi.com/docs/Troubleshooting
And if that doesn't help at the end of the troubleshooting guide they have links to their own support channels
Bad caps can definitely be the cause of no sound, I had the same problem on a Mac SE/30 recently. Replacing caps C3 through to C7 fixed it.
Console5 sells cap kits for the SE/30. Here's the cap kit for the logic board.
There's prior art with this Mac SE & SE/30 version: https://github.com/dekuNukem/PicoRC/blob/master/mac_se_se30.md
I'd imagine it'd require some pretty light changes to make it work with the Classic & Classic II
The pinounts are quite different so you'd need to make a custom cable:
Classic II pinouts https://old.pinouts.ru/Power/macclassicpower_pinout.shtml
SE pinouts https://68kmla.org/bb/index.php?attachments/se-30-logic-board-pinouts-and-caps-png.33698/
Edit: Updated SE pinouts to the right ones
Surprisingly some non-company backed open source projects do provide support, bluescsi being one of them.
They have a troubleshooting guide which has this at the bottom if the guide doesn't help.
Here are some more BlueSCSI v2 tray mounts I found:
https://www.printables.com/model/813709-mac-se-and-se30-bluescsi-v2-expansion-port-bracket
https://www.printables.com/model/661675-desktop-bluescsi-v2-mount-for-board-revision-20231...
Thanks that's helpful. In my case the modern 4x4MB sticks I bought allow my SE/30 to boot but they weirdly show up as 24MB. I've gotten NOS 4x4MB sticks and they show up as the expected 16MB, so I'm pretty sure the modern ones are faulty (they don't work in my Quadra 700 at all, and that's got...
Retro Recipes also tried this before with some decent results:
If it makes any difference, I'm in NorCal, RetroRecipes is in SoCal.
I haven't seen any follow ups from RR, but I'll be tracking how it goes over time. I only really did this out of sheer laziness, I honestly wouldn't be surprised...