I built a 20hp rotary phase converter and have been running this lightly used machine for a few weeks now. Robert E. Morris rebuilt the spindle motor prior to my buying it from a dealer. Fired it up after running it last night and it blew the F7 fuse (Alarm 3 on top board). Maintenance Manual says to check the Transistor units buy measuring the resistance between base & collector/emitter but I seem to be getting good on the first half and bad on the second half of each one. Do I have to remove any terminal wiring before checking this?
As a side note, the line running down to my barn is pretty long and I believe there is a small voltage drop on surge ( lights flicker/dim ). I can't comfortably get it over about 2200 RPM before the spindle drive starts to 'cog'. Will only rev up to 1100 RPM from stop so I start at 6" diameter G96 and feed it down to the work with a G50S2200. Seems to have been working OK till now!
Any insight into this repair will be greatly appreciated!!