Recapped battery bombed SE/30, 3 years later can't boot from HD or floppy.

[Vahan]

Hello, everyone!

I recapped a battery-bombed SE/30 about 4 years ago, replacing all the electrolytic caps with tantalum ones, and got it fully working. Recently I decided to check the Mac and sadly it wasn't booting from the internal scsi drive AND the floppy. Both the hard drive and floppy spin up yet I get the floppy with a question mark. Also, the startup chime is distorted - my guess is I didn't wash the board well enough and somewhere the electrolyte has continued to eat the traces away.

Here are the photos I made during the initial recap before touching the PCB, they show the corrosion near UD8, and UE8 from the leaked C7 and a slightly less affected area near the C8, C9 and C10 next to the SCSI chip. The board took an iso bath after and worked great.

Any ideas on what traces would be the proper starting points on the PCB to check for the culprit? To my understanding, the SCSI/SWIM issue is separate from the sound issue, so I have two areas to check and repair.

 

[chiptripper]

Yeah probably two separate issues.

So these aren’t recent pictures, then? I do see a lot of evident corrosion right in the midst of that sound circuitry. Not seeing anything obvious near the SWIM and SCSI chips, but quite plausible there’s a bad trace or resistive via hiding in that cluster. (I find a lot of vias need their solder refreshed before an SE/30 will run stably.)

 

[Vahan]

I took some time and checked some traces and cleaned the sound area a bit more with a Q-tip and iso, after reassembly the sound is now gone completely. The Vdd and gnd pins of the UE10 are slightly more corroded than the rest. I also made some new 7.1, 7.5.5 boot floppies on my PowerBook G3 but still can't boot from them

 

[zigzagjoe]

As chiptripper said you probably have a rotten via or bad trace. You could start by toning this out.

 

[Vahan]

To be honest, I'm more concerned about the floppy/SCSI side of things. Any similar diagrams for that part of this story? The floppy drive is a known good one, that worked before, now when I insert a floppy, I don't hear the head assembly seeking, just a 2-sec delay and eject with an X icon. The same with the internal hard drive...

 

[zigzagjoe]

Oh, fair point, I missed that. That is a bit more important. Here are 3 sets of schematics to reference.

Apple ones are best accuracy but poor quality scans.
Bomarc are better quality scans, a little annoying to read, but reasonably legible. Contains some errors (this is a third party schematic).
Schematic redraw is a recent effort to redraw based on Apple originals - best legibility, but it has many errors.

 

[Vahan]

Yeah, I got all the schematics and pinged the ribbon connectors to chips, as well as the D0-D7 and A0-A2 lines between the SCSI and SWIM, they checked out, also both have power and ground. Gonna refresh the solder joints on them and the ASC and report back for more hive-mind insights