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So I’m pretty sure the NCR 5380 SCSI chip on this Mac Rescue expansion is bad so I’ll be replacing it. Since I have to take the Mac Rescue off of its socket anyway, it’s interesting to verify that this is really a cleanly reversible expansion. With it removed, the Mac fired right up with 128K of...

As for why is has its own 68000 instead of using the original, my theory after looking closely at the board is that it allows this board to more cleanly intercept the address and data lines to allow for expanded RAM. Other RAM expansions that I've seen for the 128k involve varying levels of...

Wow! What luck to find the Mac Rescue manual! Thank you so much for scanning and uploading it. It’s good to know that it is configured correctly for the 4MB that it has onboard. So I went ahead and took out the SIMMs and while I didn’t see any corrosion, I cleaned the contacts with a fiberglass...

I was recently given a Macintosh 128k by an old friend and it’s definitely not a normal one. The first clue it was special was a DB25 connector on the back that looked like a SCSI connector. Opening up revealed that it has a Mac Rescue expansion board with SCSI, populated with 4MB of RAM. The...

Getting the floppy with question mark is a pretty good sign that the motherboard is not yet ruined. There is a small chance that there is a problem with the SWIM if booting from floppy or the SCSI controller if booting from HDD, but it is more likely that the HDD no longer works and they don't...

If you don't want to DIY, Keystron is another source of new SIMMs using reused & NOS memory chips similar to Memory Masters. I've had good luck with them in my Macs and they're reasonably priced. They sell on eBay but the prices in their own online store are better...

I've been unable to find an exact replacement so far. I've tried using this other Alpha pot: https://www.taydaelectronics.com/b-1m-ohm-linear-taper-potentiometer-spline-shaft-pc-mount.html It has the right lead spacing and body size, but has a few downsides: the leads have to be bent straight...

I just repaired an SE board in similar state, but the SCC was in somewhat better shape. Replaced all the passives and the 26LS32s in the flooded area, needed a bodge on C13 to ground but it is working fine now!

Looks like it – the note is also on the Mac Plus's page: https://support.apple.com/kb/sp190?locale=en_US

Apple's own spec pages for the SE and Classic (still hosted on support.apple.com!) both state that 2-chip SIMMs are not supported (and by extension, probably 3-chip SIMMs also, as the 3rd chip is used for parity which is ignored): "This system cannot use two-chip 1MB SIMMs."...

Amazing restoration so far! I'd try dunking the chassis in Evapo-rust (or a similar chelation-based product like WD-40 Rust Remover Soak or Blaster Rust Remover Bath). I've had excellent results with removing the rust on battery bombed compact Macs with it. Here's the results of soaking an SE...

I thought Corona Dope was for resealing flyback transformers. It cures hard so wouldn't be good for the anode cap.

To kinda answer my own question, after measuring an un-smashed pot on another analog board, this Alpha potentiometer, part number 3RP/1612N-AA2-B1M seems to be the closest match. Of course, I can't find any place that actually stocks it. I'm assuming I want linear taper, not audio taper for the...

I’m trying to fix no video on this Macintosh SE/30 that looks like got dropped on its front left corner. The brightness pot is pretty smashed up and reads as an open circuit on my multimeter. Does anyone know if this is a common part that’s still available today, or if there are any substitutes...