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Old 6th August 2007, 10:16 AM   #11
twon007 is offline twon007  United States
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hey just curious because i cant read the switchers in power supply. what are they supposed to be? my amp has obiuously been touched asthe gate resisters arent right. they are lying sideways.
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Old 6th August 2007, 12:54 PM   #12
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I don't have any photos of the power supply transistors but I think they were IRFZ40s. If I had to replace them now, I'd use IRF3205s. The drive circuit should be able to handle driving the 3205s with no problems.
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Old 6th August 2007, 06:07 PM   #13
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WOW now thats old, It has Mosfet outputs with TO-5 driver devices. This must be 1 of a few of these that was ever made, as it is not the run of the mill PPI amp.
Are there anymore pics available ? And what is covering the power supply sections in white ??
THX for a original and rare piece of PPI history
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Old 6th August 2007, 06:32 PM   #14
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Under the tape near the center of the amp, there are 6 Cornell Dublier caps and a huge laminated core inductor. I puleed 3 of the caps to check them and all three were still above their rated capacity. They passed all tests I could perform.

I have more photos. I was in a hurry when I took them so they're not great. What areas do you want to see?

This amp was made when someone had pride in the equipment they built. The bottom cover was tempered spring steel. The only cover I've seen that I trusted to properly clamp the transistors.
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Old 6th August 2007, 11:42 PM   #15
twon007 is offline twon007  United States
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Quote:
Originally posted by Perry Babin
Under the tape near the center of the amp, there are 6 Cornell Dublier caps and a huge laminated core inductor. I puleed 3 of the caps to check them and all three were still above their rated capacity. They passed all tests I could perform.

I have more photos. I was in a hurry when I took them so they're not great. What areas do you want to see?

This amp was made when someone had pride in the equipment they built. The bottom cover was tempered spring steel. The only cover I've seen that I trusted to properly clamp the transistors.

hey can you help me? does anyone have a schematic for this one? or can someone tell me what i did wrong? amp stays lit without remote. all i did was change the drivers, now it does this.
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Old 7th August 2007, 09:05 PM   #16
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Which drivers did you change?

When you say it's on, do you mean the power supply is staying on (oscillating and producing rail voltage)?

If so, is it still 'thumping' like before?
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Old 7th August 2007, 10:33 PM   #17
twon007 is offline twon007  United States
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Quote:
Originally posted by Perry Babin
Which drivers did you change?

When you say it's on, do you mean the power supply is staying on (oscillating and producing rail voltage)?

If so, is it still 'thumping' like before?

ok this is what i did. i took the cover off after the thump in the speakers, found the mpsu devices cracked open and replaced them with like equivelants. well as you could imagine i had to clip the cooling fan leads so i could work. did the replace and powered her up and saw sparks coming from the wire. then it would not power up after that.
what could i have fried?
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Old 8th August 2007, 12:18 AM   #18
twon007 is offline twon007  United States
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Quote:
Originally posted by Perry Babin
Which drivers did you change?

When you say it's on, do you mean the power supply is staying on (oscillating and producing rail voltage)?

If so, is it still 'thumping' like before?

no it is not even doing that anymore. i replaced two small to92 transisters in the area of where the remote wire came in but this did not fix. new parts where replacements NTE287 in place of mpsa06. replaced those mpsu51 and mpsu01 whith replacements #s NTE187 in place with the 51, and NTE48 in place of the mpsu01,. do those parts sound correct?
but this is where i said the amp wouldnt shut off. its cause i noticed that i had the NTE48 in backwards. those where the gate drive transisters i believe. what do you think i should check? ive been going backward toward the sg3525 and everything seams ok so far,but i am not sure what i should look for. the sg3525 has 5 volts from pin 11 and 14 without the remote hooked up. but no led indicater though. ever since the piece was in reversed i think i did damage. wish i had a schematic or some help navigating through it. thx in advance. twon007
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Old 9th August 2007, 01:16 AM   #19
twon007 is offline twon007  United States
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Default fixed it 2350dm back upn runnin!

it was the npn pnp's for the remote. i am happy because i got music comuing out of both channels, and bruidges. all is fine sound wise and gain wise. the low impedence light comes on and the red on-led is very dim. do you think it's just cause of the short that was in the remote region?
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Old 10th August 2007, 09:49 AM   #20
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On some (maybe all) of the PPI amps, the power LED is powered by the regulated 15v supply. If the op-amps have 15v on their power supply pins, the LED could be weak or the series connected current limiting resistor could be out of tolerance.


The low impedance circuit is probably driven by a transistor connected across the emitter resistors. The two low impedance driver transistors for the left and right channels would combine and pull down the base of a PNP transistor (which would switch the PNP transistor on). The collector of the PNP transistor would drive the LED 'on' either directly or through another transistor.
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