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Old 12th August 2004, 01:28 AM   #1
Adam M. is offline Adam M.  United States
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Question Finally building... Power supply question

I am finally getting around to building my amp thanks to the help of everyone here, and am at a stopping point on the power supply. How does one wire one of the parts express Avel transformers to get +- dc voltage? Using a bridge on each secondary, I can now get + voltage and ground out of each secondary, but the voltage is positive on both. I was looking at a schematic from SL's website: http://web.archive.org/web/200106191...cs/3886pwr.gif

and it seems that 2 of the 4 wires on the output must be tied together to get the ground... which doesn't seem right to me...

I would welcome any suggestions.
THanks,
Adam
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Old 12th August 2004, 01:42 AM   #2
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http://www.diyaudio.com/forums/showt...264#post359264

don't thank me...

Thank Brian.
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Old 12th August 2004, 02:04 AM   #3
Adam M. is offline Adam M.  United States
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Wow, was that buried in that thread. I got the primaries wired in parallel, its the secondaries getting connected to the bridge(s) that have me confused...
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Old 13th August 2004, 01:07 AM   #4
Adam M. is offline Adam M.  United States
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Default Moving forward slightly...

I figured out how to get the +- rail voltage, and what I presume is a ground. I am taking ground to be the connection between the 2 secondaries, which gives me proper rail voltage, and possibly a PS ground. But, when I measure the voltage at that point relative to the ground prong on a nearby plug, I see 25VAC. Is this an accurate ground?
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Old 13th August 2004, 03:01 AM   #5
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NO NO NO

There is nothing like a ground on that transformer. The only ground (until after the rectifier board!) will be the third wire of the AC supply coming begore the transformer. Black~ hot, White~neutral, Green~ground.
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Old 13th August 2004, 03:02 AM   #6
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...and that green wire goes to the enclosure (chassis).
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Old 13th August 2004, 03:35 AM   #7
Adam M. is offline Adam M.  United States
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Where would I draw the ground from after the rectifier board? Right now I have the primaries in parallel, the secondaries in series, with the input to the bridge coming from the other 2 ends of the secondaries, which gives me +-35v relative to the middle of the transformer. How do I wire the thing to get +-35v relative to ground (a real ground this time) instead? Thanks for the help.
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Old 13th August 2004, 01:40 PM   #8
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After the AC supply ground goes to case, then that's the only real ground from this point on. You will tie all other grounds to the "star ground".

see grounding

additionally for a graphic rep...

more
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Old 13th August 2004, 08:42 PM   #9
Adam M. is offline Adam M.  United States
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Default negative rail voltage

Where do I pull the negative rail voltage from? I can only get -rail relative to the middle of the 2 secondaries, not relative to a real ground. I have tried with both 1 and 2 bridges, and can't visualize what needs to happen to get the -rail. Any suggestions?
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