General Category > Lisa Troubleshooting and Repair
Will the Lisa return an IO error without the "Lite" Interface Card
sigma7:
I forgot that the Lite Adapter connects RData to Sense, which goes to U3B on the I/O Board, so that's another potential victim.
Sense is used to read disk-in-place and write protect, while RData is for the actual data stream. These were unique signals for the Twiggy, but since the 3.5" drives combine them as one, the Lite Adapter ties them together.
friedboard:
Wow, thank you so much for such detailed analysis! I am going to purchase some replacements for these chips since luckily they look generic. Is there any chance that the damage could reach into the actually floppy disk controller?
Also, would it be easy to tell what the damages would be if they were plugged in the other way around (180 degrees) since I did try it with another board but that didn't destroy the esprofile. Thank you!!
sigma7:
--- Quote from: friedboard on August 08, 2025, 03:19:53 am ---I am going to purchase some replacements for these chips since luckily they look generic. Is there any chance that the damage could reach into the actually floppy disk controller?
--- End quote ---
Almost all the parts in the Lisa are generic, although some are so long out of production that they may be hard to find.
The FDC in the Lisa is made from discrete parts (aside from the IWM in the 2/10), so I'd say those components are actually parts of the floppy disk controller.
Yes, over-voltage damage can cascade through one part to another, and even from one part to the power supply rail to the whole machine. At some point you'll probably need to do some troubleshooting at the signal level, but replacing the parts obviously at risk may solve the problem. I suggest using sockets when replacing the chips.
--- Quote ---would it be easy to tell what the damages would be if they were plugged in the other way around (180 degrees)
--- End quote ---
I think so; draw a diagram of how the signals line up between the Widget Header and the Twiggy Header and see if you come up with the same list that I did. Then do another diagram with one of the pinouts rotated and repeat.
However there are a limited number of signals involved; probing with a voltmeter or oscilloscope might be more informative.
friedboard:
Wait, just noticed that my IO board is a 820-4033-A with 3 large chips on the top left. Mine is a Macintosh XL board then?
I don't have some of the chips you mentioned above like the U5B
sigma7:
--- Quote from: friedboard on August 08, 2025, 06:57:26 am ---Wait, just noticed that my IO board is a 820-4033-A with 3 large chips on the top left. Mine is a Macintosh XL board then?
--- End quote ---
"Macintosh XL" is not sufficiently specific, since for a while, any Lisa running MacWorks was called an XL. The I/O Board with the 3 large chips is often referred to as the "2/10 I/O Board"
In which case, (edit: this issue only applies to 400K single sided drives:) a stock Lite Adapter is not going to work, as the 2/10 I/O Board incorporates its electronic functionality, but not the connector adaptation.
So back to this...
--- Quote ---a self-consistent hardware configuration... ie. if you are trying to use a Lite Adapter, you should have a 2/5 I/O Board (two, not 3 large chips at the top left), a 2/5 Motherboard (with a rear panel parallel port), and 2/5 chassis wiring (two 26 pin ribbon cables in the drive cage area).
--- End quote ---
You have (double check and adjust if incorrect):
- a 2/10 I/O Board (with 3 large chips at the top left)
- a 2/5 chassis wiring harness, with 2 ribbon cables with 26 pin connectors in the drive cage (and no 20 pin connector ribbon cable)
- a Lite Adapter
Which motherboard do you have? Does it have 2 DB-25 connectors along the back or 3?
Does the Lite Adapter have any modifications to it (eg. wires added to the top or bottom)?
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