Re: 13.8V HW1200R-20A repair

Mechdave,
I have just fixed my HW1200, it was a bit of a mission but sounds like you might have similar problems. My output voltage varied around 6 volts. I replaced all the caps apart from the two large ones in the main 340V dc supply to no avail. Finally I checked the supply voltage to the 494 (pin 12) which should be greater than 7 volts - it was not hence the reg output could not get up to 5 V either (pin 14). Turned out Q3 (S8050s NPN) had gone leaky dragging down the 494 supply. I replaced Q3 and Q4 with a couple of BC337s and away it went....

Re: New Members - please post your introductions here

Hi all, I'm Ian and have been involved with electronics since I was a teen though in those days it was valves and high voltages and big transformers. Over the years I have fixed the usual TVs and stereos etc for a crust either working for myself or repair companies. The latter part of the career after doing and engineering degree was with a military company doing some secret squirrel stuff having interesting times in foreign lands and I mean foreign.
I like probably all of us here enjoy fixing things, usually around the...