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Help with power supply??? N.Pass A75
Help with power supply??? N.Pass A75
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Old 6th July 2001, 03:25 AM   #1
harbin is offline harbin
diyAudio Member
Join Date: Jun 2001
Location: Chicago
I am building the N. Pass A75 and I have run into a snag. As Nelson suggested I tested the reg. supply and I am getting a steady 50v.

The problem is when I put in the fuses for the unregulated suppy. I get ~44v DC which is what I would expect, but then he says to measure the AC. When I measure the AC across one of the cap using a VOM set on AC I get about 100v!

What could I have possible done wrong? it is such a simple circuit.

I am using a 31v tranny which I doulble checked is wired up correctly. I bought some 30000uf caps surplus they are marked McKintosh, they look good, but I have no way that I know how to test them, other than that the rectifiers are new from digikey. I have also placed bleed resitors across the caps to bleed them down when not in use.

The tranny buzzes for a fration of a secound, as it charges up the caps. Then I get the ac. When I turn it off the caps then beed off through their resistors.

I don't have a clue unless the caps are bad?

ANyone had any experience like this?


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Old 6th July 2001, 04:26 AM   #2
grataku is offline grataku  United States
diyAudio Member
Join Date: Dec 2000
Location: -
Let me get this straight...are you measuring with a voltmeter on AC setting across the + and - of an electrolytic filtering capacitor after the rectifier?
If so you are driving your voltmeter crazy that's all.
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