Different animal there Steve!!! Those POW Con 300ST's were exactly like Gerald mentioned... Btw, Miller did NOT Buy their technology at all in the late eighties/early nineties!!!
I used repair these early inverters while the "suit's" were selling these like hotcakes to many folks like the USN for instance, mainly because of their portability...
Btw, that ticking sound is most definitely the capacitors discharging like Gerald mentioned, and Miller already had their first Inverter model out before 1989.
The biggest problem with those inverter power sources were the lack of shock absorbers or vibration isolators incorporated into the mounting of the main ceramic inductors which were extremely vulnerable to having hairline cracks propagating due to the lack of some sort of shock absorbing mounting device designed into the system in order to dampen or counteract the effects of sudden impacts of varying intensities originating from hitting objects or anything else, and operators dropping the power sources either unintentionally or for research purposes in determining what were the limits these power sources had when it came to their ruggedness!!! Oh, and those ceramic inductors cost a pretty penny to replace which inevitably
IGBT's were first used in inverters by the European & Japanese Welding equipment manufacturer's... We followed suit ;)
Just as Gerald mentioned in this thread previously - these pwoer sources were good machines that worked very well when they were given just a tad of TLC yet, if they weren't taken care of as they should have been in the first place, the first part that would most likely fail were the ceramic inductors or the capacitors which had lousy quality controls built into each and very one of them!!!
These Pow -Con's, and myself go way back just as they go back in the day with Gerald also - son ;)
Darn good little workhorses they were when "firing on all cylinders - so to speak!!!" I personally worked with over 100 of these and similar puppies ;)
Respectfully,
Henry