Hi all! Sorry for the bit of a longer post, I'm a rambler 
Some backstory before getting into the problem: I got this Mac SE SuperDrive back in 2014 for $15. I tested it out by powering it on and it got to the "disk not found" icon, but since I didn't have any compatible mouse/keyboard and no floppies, and I was a broke teenager, I couldn't do anything with it. I did open it up and notice that it was pretty badly corroded, and was smart enough to take (what was left of) the battery out, but then I put it in my closet and moved on to the next hobby.
Fast forward about a dozen years to a little over a month ago, I get an itch to mess around with it. I remember it working, and I've forgotten about the corrosion by this point. I power it on.... and am met with either garbage video, a corrupted sad mac screen, a blank gray screen, or horizontal stripes, randomly when it's turned on. If left on, it'll randomly flip between these options every so often. No sound or chimes or anything from the speaker.
I'm not a broke teenager anymore (thank god) so I wanted to take it on as a challenge. Here's what I've done:
Some backstory before getting into the problem: I got this Mac SE SuperDrive back in 2014 for $15. I tested it out by powering it on and it got to the "disk not found" icon, but since I didn't have any compatible mouse/keyboard and no floppies, and I was a broke teenager, I couldn't do anything with it. I did open it up and notice that it was pretty badly corroded, and was smart enough to take (what was left of) the battery out, but then I put it in my closet and moved on to the next hobby.
Fast forward about a dozen years to a little over a month ago, I get an itch to mess around with it. I remember it working, and I've forgotten about the corrosion by this point. I power it on.... and am met with either garbage video, a corrupted sad mac screen, a blank gray screen, or horizontal stripes, randomly when it's turned on. If left on, it'll randomly flip between these options every so often. No sound or chimes or anything from the speaker.
I'm not a broke teenager anymore (thank god) so I wanted to take it on as a challenge. Here's what I've done:
- Neutralized/cleaned off as much of the corrosion from the logic board as I could.
- I also cleaned off the loose rust from the chassis and power supply cage above the bomb blast. No other board or components seem affected.
- Made sure there weren't any broken traces I could find.
- Somehow despite the corrosion erasing most of a steel bracket from existence, the solder mask on my board withstood the torture. the goat honestly.
- Replaced all the passives (except the inductors).
- Probably jumped the gun with this one, but I figured I might as well since I had to replace a handful that had literally rusted away. It ended up being a really great way to get back into soldering and get myself really familiar with the board, so I don't regret it even if it wasn't all necessary.
- Replaced the speaker's wires since those got corroded as well.
- Speaker works when it's given voltage directly, but still no sound or chimes on startup.
- Replaced a pin on each of the ROM chips since they were fragile from rust and fell off.
- All the pins on the ROM chips have good connection to the logic board now.
- ...I recreated a Bourns filter from scratch because one of mine was shot.
- Pretty proud of this job actually, despite using 24ohm resistors since I didn't have 25ohm, it should be within tolerance? right?
- I think I have another shot one (the one right above C11), but I don't want to take the time to replace it unless there's a chance it's the source of the problem.
- The reset pin is actually at +5V after a half-second or so after starting up, which is odd since it looks like a lot of the people with the same display garbage have a reset stuck at 0V.
- The reset button also works to pull the reset pin low, but it doesn't seem to affect much on the display.
- The clock pin is getting a frequency of 7.833 MHz, which seems to be right?
- I don't have an oscilloscope, just a multimeter.
- I know how to read a schematic, but I don't know enough to deduce the logic of circuitry like this I also can't find the schematics for the SE FDHD logic board anyway, so if those are a thing we have, could someone link it for me? It'd help with finding points to test trace continuity.
- I'd rather not buy another logic board for parts unless absolutely necessary, but I'd be willing to get a reloaded board and transfer all the stuff over if this ends up being an issue with traces in inner layers or something else unfixable.
