General Category > LisaList2
Does anyone have a spare Lisa motherboard?
AlexTheCat123:
I have some old Macs with 800K drives, so making floppies should not be a problem. I will try to get the Lisa working first and then I might try to fix the serial ports if I can get it powering on.
Lisa2:
--- Quote from: rayarachelian on November 07, 2019, 06:19:17 am ---Now, if you have a classic 68k Mac that has a GCR capable floppy drive, even if it's a super drive, you should be able to make Lisa floppies, though one with an 800k floppy drive is preferred due to the head width.
--- End quote ---
Ray, I think you are remembering an issue with PC 5.25" HD drives writing DD formats.
To clarify (not to hijack this thread), the number of tracks (and head width) is the same for the Macintosh DD (800K) and HD (Super) Drives. Some later mac FDCs had issues writing Lisa disk images in a way that the Lisa's FDC prefered, but the drive itself was never the issue.
Rick
AlexTheCat123:
I have cleaned up the corrosion, replaced several corroded parts on the motherboard, and have tested every single connection on the board (which took a very long time) and there is an improvement! The light on the power switch illuminates when I press it and will stay on for a short period of time (maybe about one second), but then turns off again. Is this a common problem and does it narrow down any potential faults with the computer?
rayarachelian:
--- Quote ---I have cleaned up the corrosion, replaced several corroded parts on the motherboard, and have tested every single connection on the board (which took a very long time) and there is an improvement! The light on the power switch illuminates when I press it and will stay on for a short period of time (maybe about one second), but then turns off again. Is this a common problem and does it narrow down any potential faults with the computer?
--- End quote ---
Yes! That's a great sign!
Most likely your next issue is either 1. the I/O board traces around the COP421, or 2. the power supply is weak and needs new capacitors. 2 (power supply capacitors) is even more strongly indicated if you hear some ticking, though the light on the switch would only stay on while the button is pushed, if it stays on after you let go of this switch, it might not be this, but I'd check the large capacitors in the power supply either way, if you see cracks in the large rectangular yellow ones (if they're yellow and somewhat transparent, they're the original ones, and are likely long dead), and the large cylindrical electrolytics.
I've also seen this caused by the floppy cable inserted backwards in the LisaLite card.
AlexTheCat123:
I think I'm making progress! I have patched every bad trace that I can find on the I/O board and now the power light will turn on and stay on when I hit the switch. A transistor (Q3 or Q4 I think) let out some magic smoke when I turned it on for the first time, but it seems to be part of the audio amplifier, so I don't think it is necessary, at least for now. If I press the power switch again after turning the computer on, it will turn back off, but only if I let it run for about 20 seconds before trying to power off. There is still nothing on the display, though. I don't even hear the high-pitched whine that CRTs make when they are on, so I suspect that there is something wrong with the circuitry that drives it. Does the CRT turn on when you press the power switch or does it require a signal from a board in the card cage before it energizes? If it requires some sort of signal before it turns on, then I probably have a problem with the CPU or I/O board, but if it turns on with the rest of the computer, then I may have to mess with the video board to make it functional.
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