LisaList2

Thanks for the link!

My follow up question was going to be whether or not an isolation transformer would be a suitable solution, and if would be safe to use on the occasion the Lisa gets used.

Yep, this is definitely a known issue with vintage power supplies -- happens with both unrestored and recapped units. Thread here:

https://forum.vcfed.org/index.php?threads/ground-leakage-in-h704a-power-supply.1251794/

This often causes problems at VCFWest, as the outlets in the walls are GFCI!

I've run into this same issue, with multiple 1.8A power supplies that I've recapped. The behavior is inconsistent, too. Sometimes the PSU will work as normal for days at a time, and then at other times it'll trip the GFI right away when plugged in, or powered on. I have not been able to track this down, but there does not seem to be an issue with my soldering. Hmmm...

The outlets in my home office are connected to two separate circuits, each with GFCI. I've just realized that when I've had a Lisa plugged in (often powered off) the GFCI outlet will at some point trip. Took a while to put two-and-two together, but it's fairly reproducible at this point. The machines work fine in other locations, but can't live there permanently. Is there something about the power supply that can be pinpointed as the cause for this behavior?

the voltages from the power supply are correct...

I take that as indicating you have some kind of voltmeter.

If you watch the DC voltage at each of the signals listed while inserting a floppy disk, you might observe some activity. Which ones are active and which ones are not may reveal the point of failure (or more likely, suggest further measurements to make to better localize/determine the failure... troubleshooting is an iterative process.)

ie. connect the voltmeter to a signal (and the other lead to ground); insert a floppy while watching the voltage to see if it fluctuates, as well as the average reading, record your observations, eject the floppy, repeat with each of the other signals. Then report what you've observed and further suggestions can be made.

It will be useful to know what kind of voltmeter you have since different voltmeters respond differently to fluctuating signals.

Wanted: Looking for LISA keyboard menu cards

Yeah, I think all the voltages from the power supply are correct and the boards pass basic startup and extended tests so that is a good sign! I believe what is broken might be a chip specifically for reading floppies

replaced the lite adapter but it's still the same. Do you know ...

Tracing those signals to the 2/10 I/O Board:

Phi A comes from U2F-3.

/WREQ comes from U1C-13.

RData goes to U1C-2.

Sense goes to U3F-5.

MT1 comes from U9A-3.

It is possible that there is some other problem that won't be repaired by replacing all the parts, so some troubleshooting may be more expedient... do you have any test equipment (DMM, Logic Probe, Oscilloscope, voltmeter, etc.)?

I had played around with this a bit before all the recent work by Alex and others....

As I understand it, LisaGuide on a Twiggy is self-contained. Of course a Twiggy holds more data than a single sided 3.5... but many systems have double sided 800k drives these days. Would it be possible to build a LisaGuide 2.0 disk that's bootable?

I'd played around with this some, trying to modify an installer floppy, but couldn't get it to work. Switching out what I think was the patched for double sided drives Sony driver would make the disk not bootable.

-J

replaced the lite adapter but it's still the same. Do you know what U5B-13 is on the Lisa 2/10 board?