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Old 17th June 2008, 09:08 PM   #2481
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nelson - i wired it like the diagram in post 2314-but instead of a star it is a short wire with power supply on one end and signal grounds on the other,next to the thermistor-which goes to the chassis along with the power plug earth .here is a pic of the bottom of peter's supply board.the two traces in the middle are the grounds which i jumpered together in 2 places in the middle-top half holds the crc and the bottom half holds the other 2 caps and i have a jumper wire on the bottom side going from + to + on the caps on each side of the resistors for the positive supply. negative supply is the same but caps reversed. what improvements could be made???????
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Old 17th June 2008, 11:24 PM   #2482
tms0425 is offline tms0425  United States
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Quote:
Originally posted by Nelson Pass
I looked at the photos and I couldn't clearly see how the
grounding is arranged, and for that matter, I can't tell how
the two power supply boards are used.
Yeah, I wondered that too. I used PD's power supply boards just like those with two Plitron 18vac x 2 transformers. To get the 36vct it uses two FW bridges per channel. With some jumpers it can use just a FW, but I'm not sure why you'd do that. I would just start with a single power supply board with two FW bridges assuming the transformer there has dual 18vac windings. This should yield the +/-24vdc and you can decide if it's the PS or the signal boards that cause the problem.

Tom
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Old 17th June 2008, 11:39 PM   #2483
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so the F4 has been on the bench turned on for 8 hours hooked up to some small rat shack speakers and i could swear the hum is less now that the amp is warmed up--weirdness #2 i went to hook up a pair of ev horn speakers to the amp and when i plugged one channel in with both speakers being driven by the same channel the hum increased--almost double the volume in the rat shack speakers!!! stumped in missouri
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Old 17th June 2008, 11:41 PM   #2484
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ground loop problem with your source perhaps?
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Old 17th June 2008, 11:47 PM   #2485
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if i used one board for the whole supply i would have to use 30,000 uf caps --- i am using 15,000uf caps and the other half of each board is just holding the other 2 caps
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Old 17th June 2008, 11:49 PM   #2486
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this amp hums even with no input from a preamp attached--rca's plugged in from preamp or unplugged no difference in hum level
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Old 18th June 2008, 01:32 AM   #2487
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No cold solder joints? Also, I'm curious about this pic (where are the extra rows of resistors that parallel the first?):
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Old 18th June 2008, 01:42 AM   #2488
tms0425 is offline tms0425  United States
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Quote:
Originally posted by bubba177
if i used one board for the whole supply i would have to use 30,000 uf caps --- i am using 15,000uf caps and the other half of each board is just holding the other 2 caps
Not sure I quite understand that, but do you have a good +/-24vdc to both boards?

Can you move the ps boards, bridges, ac wiring away from the input wiring temporarily to see what happens?
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Old 18th June 2008, 01:53 AM   #2489
tms0425 is offline tms0425  United States
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Quote:
Originally posted by carpenter
No cold solder joints? Also, I'm curious about this pic (where are the extra rows of resistors that parallel the first?):
Didn't notice that. Since he's only using half the boards, maybe that's the bleeder resistor?
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Old 18th June 2008, 02:02 AM   #2490
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Quote:
Originally posted by tms0425


Didn't notice that. Since he's only using half the boards, maybe that's the bleeder resistor?

I take it that he's using two pcb for the F4 PS. Straying from the norm will get you into deep water in a hurry. I used Peter's standard layout and my 110db 1w1m horns are very quiet!
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