Well I survived the 250VDC build, test and implement.
This is interesting, the original SSL 250VDC supply, as it turns out, had drifted upwards to about 295VDC. This gave all the plasma meter units a soft focus appearance, a bit like out of focus. The offending part was a 220K carbon film resistor that helps define the regulated output voltage, it had gone way outside its tolerance band so the 50K trim pot had no chance of lowering the voltage back to 250V. There may be a few others out there that could benefit from a very simple fix, just replace the offending 220K resistor on the PSU mother board right beside the three trim pots associated with the 250V regulator card.
Anyway I built my own 250VDC supply and popped it into an unused power and chassis, great for heat sinks, mains connection etc and hooked it up to the Console after a bench test of course. Result...pin sharp plasm metering, right on focus, a thing of beauty. Not bad for a thirty year old board.
Oh yeah the 250V (plus small change) is holding rock solid and showing 25mV of ripple at full tilt.
