Has worked fine for a long time.
However, now it will work for about 10 minutes at the start of a session, and then quit.
The Z4000 meter indicates a short.
No way to get it working the rest of the day.
If it sits overnight, it will work for about 10 minutes the next day, and then quit.
When I unhook the incoming power wires and connect them to the track, everything runs.
Therefore, problem appears to be in the PowerMaster.
Any suggestions?