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| Trouble tracking down bad RAM in a Lisa 2/5 | |
| Posted by: redruM69 on 2018-05-02 14:47:52 I recently acquired a Lisa 2/5 as a project. PSU fixed, corrosion repaired. It has 2x 512K RAM cards in it. Getting an error 70. I have narrowed it down to 1 card. The bad card is in slot MEM 1, MEM 2 left empty. Enter service mode, Read memory location $186 gives 0000 0000 0000 0004. Cool! From what I read, that means the chip at Row E, Column 20 is bad. Replaced the HM4864P-2 with a now socketed Fairchild MB8264-20, which I believe to be compatible. Still get error 70! Memory location $186 now gives 0000 0000 0000 0404 So it appears that not only did the RAM I replace still not work, but now i have a new bad bit on column 3 row E? Thoughts? | |
| Posted by: redruM69 on 2018-05-02 15:20:25 Update: RESOLVED! I made an error/typo with my original assessment. It was column 3 the entire time. I wrote down the wrong value. :x This means I accidently replaced the wrong chip! It also appears the MB8264-20 is NOT compatible. I stuck in an NEC D4164D instead, and it worked fine. Replaced column 3 row E with another D4164D, and no more errors! Now to move onto the floppy drive not working!  | |
Posted by: MOS8_030 on 2018-05-02 15:28:17Update: RESOLVED!Congrats! Good luck with the floppy drive. I gave up on mine. Even with a different drive I still had issues. I think maybe the Lisa Lite card has a problem. | |
| Posted by: redruM69 on 2018-05-02 16:10:23 I haven't looked at it close yet, but its not auto-injecting. I noticed one of the sensor LED's inside is glowing, so it is receiving power at very least. What were your symptoms? | |
| Posted by: MOS8_030 on 2018-05-02 20:01:01 https://archive.org/details/AppleLisa_RepairSunGuideDC Download the repair guide and check out the floppy section. It probably just needs a good clean and lube. But also make sure the felt pad is still there. Also, you'll need some genuine 400 or at least 800K disks. | |
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