Mastech HY3003D - “For Parts” Linear Power Supply - Part 2
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- เผยแพร่เมื่อ 6 ก.พ. 2025
- I ordered this 30 Volt, 3 Amp supply from a seller on E-Bay advertised as “For Parts, Not Working”, intending to make a repair video. The supply arrived and as seen in the video, it WORKS! BUT, in shipping to ME, some damage was done. I half-ass repair the shipping damage and adjust the Voltage and Current output values.
Link to files:
www.gswagner.c...
I have had good luck with "AS IS" Mastech PSUs. I have purchased 4 over the years. Three single voltage and one triple voltage output unit. They were way cheaper for a busted unit back then. Some needed new main filter capacitors and some had bad output transistors, one had bad TL431. The only quirk is for some reason at low current limiting they seem to oscillate and freak out. I don't recall the details exactly but I have to use them at higher current limit applications. I tried to fix them but gave up and have not tried any further at this time. I built a separate low current limited supply for those needs. Your video was timely. I was thinking of trying to fix the oscillation issue again. I thought I had a bad LM741 but that did not fix the issue. Thought I had bad caps but ESR testing didn't show anything wrong with caps. Oh well maybe I'll get lucky and find the issue. The thing that bothers me the most was it does it on at least two of the PSUs. It may be a basic design flaw.
interesting to see you go through the circuit. Thanks. I have the HY3005D-2 which uses two apparently identical boards very similar to your version, but marked hy068
Nice! It was a good deal!
Just a question.... The "fine" current front panel pot was not turned up..... Would that not possibly have been the missing few 10 or 8mA? have a good day.
Very possible!
Thanks
Steve