68kMLA Classic Interface

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512K Education with SCSI card

Posted by: petteri on 2020-03-21 14:25:44 After somewhat fixing two SE/30 I wanted another challenge. It was advertised as an 512Ke but the model is M0001D so it is education model I guess. I was told it has an 800kb floppy drive and a SCSI card. It came with a short keyboard and cable but the DB-9 mouse has been lost. It starts up with beep and the disk drive ejects unformatted floppy but there the screen is black. So I assume the logic board is fine. Gently slapping the case doesn't make any difference. So I guess I need to fabricate that CRT discharge tool and remove the analogue board first.

Posted by: MOS8_030 on 2020-03-21 14:38:37 You may find an accelerator card inside.

Posted by: petteri on 2020-03-21 14:40:54 I took a quick look inside, unfortunately the original programmer switch got damaged as the plastic was really brittle. There is a MacMemory MaxPort SCSI interface There wasn't anything really burnt or blown up on the analog board as far as I could tell without taking the whole computer apart. On the analog board the flyback transformer looks suspicious, any comments?

Posted by: joshc on 2020-03-21 15:04:58 Nice find. Flyback looks normal - most of mine look like that but work OK. If you have no picture I would reflow ALL solder joints on the analog board as a first port of call, failing this I would move onto replacing capacitor C1 before doing more troubleshooting

Posted by: petteri on 2020-03-22 08:00:40 Taking this further apart. Is this just a SCSI-adapter or some kind of CPU upgrade as well? Everything looks ok on the analog board. Caps are flat topped, no goo or burn marks. I'll follow joshc's advice and redo solders on the board.

Posted by: Crutch on 2020-03-22 09:13:40 That’s a pure SCSI upgrade.  The SCSI controller is on that PCB mounted to your floppy drive.  I can’t tell from your ROM chips in the photos (or floppy drive) if that’s a 512k enhanced, so I’m assuming the PCB may have upgraded ROMs on it also somewhere?

Posted by: petteri on 2020-03-22 12:29:33 I noticed two keycaps are somehow wobbly on the keyboard. They travel up and down fine but somehow there is something broken inside the switch. Is this common issue on these keyboards and is it possible to fix without replacing the switch?

Posted by: petteri on 2020-03-23 01:41:55 After chatting with a mechanical keyboard expert I got to know there is a chance to replace the key stem with 3d printed part (https://www.thingiverse.com/thing:2753362). Luckily I have a printer stored in the attic, hopefully PLA is good enough for this part.

Posted by: petteri on 2020-03-23 14:04:40 Alright, some progress. I went over bunch of analog board solders but most likely missed one or two... Now I get good image if I squeeze the mac from the sides. It didn't do that before so I think this one is fixable. I'll have to revisit the board once more and then it is time to find some 800kb boot disks.

Posted by: petteri on 2020-03-23 23:42:21 And it works! The second pass with new solder fixed and now the screen looks great. Any guesses whether this 512Ke with MacMemory MaxPort SCSI interface would be able to boot from a SCSI drive or SCSI2SD?

Posted by: joshc on 2020-03-24 02:14:51 That's a wonderful sight - it's a happy Mac again 🙂

Posted by: LaPorta on 2020-03-24 04:46:59 Nice job working that out! Always good to see another one working again.

Posted by: Crutch on 2020-03-24 04:51:26 Looks great, nice job!  Yes you should be able to boot from external SCSI.  In my experience SCSI upgraded early Macs usually play with SCSI devices better than a Mac Plus with native SCSI, just because the Plus didn’t originally implement SCSI in a very standard way.  I have a 128k with a Gemini upgrade + SCSI that works great with my SCSI2SD 5.5.

Posted by: petteri on 2020-05-26 07:12:25 I bought a broken Plus with a working mouse yesterday so I was able to check this better. I used my SE/30 to create boot disk and this 512Ke has 512K RAM  🙂. Unfortunately some solder needs to be redone, the screen started to flicker if I tap the screen.

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