MikkoS
New Member
- Joined
- Aug 17, 2021
- Messages
- 9
Hello all!
First time writing here. I bought an Olivetti M24 from a local guy. It was sold as a non working unit, but it was from a family who had bought it new in the 80's. The guy told me that it had worked the last time he tried some ten years ago. Since then it had been in storage. It looked very clean and nice when I went to inspect it, so I thought that maybe with a little work I can make it run again. I have salvaged some other computers and have a basic diagnosing and soldering skills. No real education in electronics thou. I got a monochrome monitor and a keyboard with the machine and also manuals and diskettes. All original Olivetti.
Now some months and a massive amount of forum reading and tinkering with the machine I decided it was time to see if I could get some help in troubleshooting this beauty. I now have three M24 motherboards and none working. Let me try to explain.
General facts
Original MB
1st replacement
2nd replacement
First time writing here. I bought an Olivetti M24 from a local guy. It was sold as a non working unit, but it was from a family who had bought it new in the 80's. The guy told me that it had worked the last time he tried some ten years ago. Since then it had been in storage. It looked very clean and nice when I went to inspect it, so I thought that maybe with a little work I can make it run again. I have salvaged some other computers and have a basic diagnosing and soldering skills. No real education in electronics thou. I got a monochrome monitor and a keyboard with the machine and also manuals and diskettes. All original Olivetti.
Now some months and a massive amount of forum reading and tinkering with the machine I decided it was time to see if I could get some help in troubleshooting this beauty. I now have three M24 motherboards and none working. Let me try to explain.
General facts
- I have tested the power source with a multimeter and according to the information in service manual it should be ok.
- It has two 360KB floppy drives.
- No bus expansion board.
- Visually in great condition.
- Came with the machine.
- 512KB RAM soldered to the MB. Empty sockets for additional RAM.
- Power LED doesn't work.
- Battery has leaked at some point. Don't know the amount of damage. Removed the battery.
- When powered on, keyboard leds stay light a second and then start blinking forever.
- Oddly, the paraller diag board gives: 80 C1 C2 C3
- BIOS v1.36
- Visually the cleanest of the three MBs I got
- Gave up with the original MB and just searched a working MB from eBay.
- Sold as 100% working. Double checked from the seller before purchasing.
- 128KB RAM soldered. 512KB on sockets.
- Power LED works ok.
- Battery has leaked at some point. Don't know the amount of damage. Removed the battery.
- When powered on, keyboard leds stay light a few seconds and then go out. At the same time speaker gives a click-sound.
- Paraller port diag gives: 00 41 42 7d
- BIOS v1.42
- When told about the first replacement MB, seller kindly send another one to replace the faulty. No costs to me.
- 512KB RAM soldered to the MB. 128KB on sockets.
- Power LED not working.
- Battery maybe has leaked at some point. Don't know the amount of damage. Removed the battery.
- When powered on, keyboard leds start blinking endlessly.
- Paraller diag gives: 00
- BIOS v1.42
- Wrote to the seller about this faulty MB too. No response yet.
- Why these odd diag codes "80 C1 C2 C3" from the orig MB?
- What MB should I focuse my efforts to or do I throw them all to trash?
- How can I test RAM modules? I just have a multimeter. Should I buy a cheap scope of some kind?
- How can I test the graphics card? Or can one deduce from this information that it is ok?
- Cross-switched bios chips between MBs. No effect. I assume that BIOS chips are ok.
- Moved all socketed ICs from 1st replacement to original. No effect.
- Piggy-Banked all socketed RAMs from 1st to soldered on orig. No effect. This was really tricky to do and I’m not sure that I succeeded with every chip.
- Checked continuity with multimeter here and there.
- Replaced socketed CPU on 2nd repl with the CPU from orig. No effect.
Original MB
1st replacement
2nd replacement
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