While searching for something that eludes me now, I ran across a Tripp-Lite PR50,
12VDC 50A power supply for around $20. The description stated it didn't work, and
nothing else was known about it. Hell, even if only the transformer was
in decent shape, it would be worth it, so a couple clicks later, and I was waiting for
another package to arrive.
This project has been in the works since it arrived sometime in early spring of 2005 (at the latest).
So, first item was to check it out and see what was wrong when it came.
The crowbar circuit had activated and the SCR was destroyed, along with
all 5 power transistors, but the regulator circuit seemed to be ok.
I replaced as needed, added a volt and amp meter, and it sat on my desk for about 9 months.
It can be seen in some of my older pictures. It worked great, and made 50A.
One day, being stupid, I didn't turn it off when working in a live amp, and shorted it out.
(Read...I stuck a screwdriver in it, and crossed the main feed while it was turned on)
Having other things going on, and way too many irons in the fire, I put it on the side, and bought
the Pyramid (bleh), as mentioned in other pages. It can be seen in these pictures also.
A couple weeks ago, I began thinking about the pr50 again, and decided to check into it.
Turns out I blew all 5 power transistors, the regulator circuit, and a few filter caps.
It is an easy fix, on all counts, so I built a new regulator using a LM317 and put in 2 2n3771's on one side,
and 3 2n3055's on the other side. This transformer has 2 secondary windings.
I had thought the regulator was set for 14.4vdc, but it seems I mis-calculated, and the output is 13.58vdc, as you can see.
Another pic of the test setup and guts of the PR50 with my new parts. The original regulator circuit had the output
posts bolted to it, and it was mounted to the inside rear left of the cabnet.
And the completed internals, as it is now. I have not tested the amperage on it yet, but will post when I do.
**UPDATE** (09/12/2010)I tried to run an amperage test on it today. It failed miserably. After checking, I hooked up the regulator
wrong, and it wasn't getting a good sample of the output voltage, so no regulation.
It was essentially a constant-current supply, set around 1 amp.
Another thing I realized, while looking into it, is all Pass Transistors should be the same type,
and preferrably from the same production run.
I will change the 2n3771's for 2n3055's when I fix the regulator.
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