General Category > Lisa Troubleshooting and Repair

Lisa Tripping GFCI

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jamesdenton:
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?

ried:
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...

pl212:
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!

jamesdenton:
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.

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