I have two of these amps on my bench currently, and both seem to have exactly the same problem - that would be failed output FETs.
Amp 1 is using IRF540 (NON N designation)
Amp 2 is using FB41N150
Both are using 10ohm gates at outputs
MPAS06 and MPSA56 drivers.
I've read in another thread that commonly these amps get upgraded to different outputs, IRF540N, FB41N150, FDP42AN15A0, or IPP200N15N3G. Some of these changes require a different GATE resistor.
Also Im having trouble identifying which OpAmp controls the bias, as I understand one which is out of spec could cause bias issues and sounds like probably should be replaced.
I clipped off all the bad outputs, leaving some which seemed to still be testing OK, and got both amps to power on without any further issue.
Can someone help me with correct component selection/combination for the output FETs, gates, and Bias OpAmp?
Amp 1 is using IRF540 (NON N designation)
Amp 2 is using FB41N150
Both are using 10ohm gates at outputs
MPAS06 and MPSA56 drivers.
I've read in another thread that commonly these amps get upgraded to different outputs, IRF540N, FB41N150, FDP42AN15A0, or IPP200N15N3G. Some of these changes require a different GATE resistor.
Also Im having trouble identifying which OpAmp controls the bias, as I understand one which is out of spec could cause bias issues and sounds like probably should be replaced.
I clipped off all the bad outputs, leaving some which seemed to still be testing OK, and got both amps to power on without any further issue.
Can someone help me with correct component selection/combination for the output FETs, gates, and Bias OpAmp?
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The phoenixphorum may be helpful. They are likely to have the most detailed information on PG amps.
I was able to repair one of these amps. The second one has a problem with the left channel being over-biased. I started chasing tail in reference to the following thread post #2 by 1moreamp. Coming up blank atm.
PG Tantrum 500.2 Output FETs
PG Tantrum 500.2 Output FETs
Im back at this one amp. Seems I may have a problem with the negative side output and rail section.
To start by referencing secondary CT, the rail voltage is slightly skewed at +36/-33vDC.
I removed all output transistors so that I could power the amp up without it pulsing and excessively drawing on the PS.
All IRF540 outputs have been removed.
The positive side output pads have ~0/+36/~0 on the pads - 1/2/3.
The negative side output pads have -24/0/-33 on the pads - 1/2/3.
I've found that I can install just 1 IRF540 into both the positive banks and the amp powers, or the negative banks and the amp powers as well; but when I have both positive and negative outputs installed the amp draws excessively.
Fist I would like to figure out why the rail voltage may be skewed at -33/+36 in this amp, and go from there.
Does anyone know these amps by chance?
To start by referencing secondary CT, the rail voltage is slightly skewed at +36/-33vDC.
I removed all output transistors so that I could power the amp up without it pulsing and excessively drawing on the PS.
All IRF540 outputs have been removed.
The positive side output pads have ~0/+36/~0 on the pads - 1/2/3.
The negative side output pads have -24/0/-33 on the pads - 1/2/3.
I've found that I can install just 1 IRF540 into both the positive banks and the amp powers, or the negative banks and the amp powers as well; but when I have both positive and negative outputs installed the amp draws excessively.
Fist I would like to figure out why the rail voltage may be skewed at -33/+36 in this amp, and go from there.
Does anyone know these amps by chance?
What's the DC voltage on the output terminals of the op-amp that's in the output section?
Or does it have audio on the output pins of that op-amp?
Or does it have audio on the output pins of that op-amp?
The regulated voltage is precisely +-14vdc referencing non bridging speaker terminals. That seems strange to me since the rail voltage is skewed.
The regulated voltage won't sag until the rail voltage gets much closer to the regulated voltage. It's essentially independent of the rail voltage, probably down to about 20v of rail.
The difference in the rail could be due to noise. If you loaded it with something like a 120v incandescent lamp, that may tell you if it's something more significant.
The difference in the rail could be due to noise. If you loaded it with something like a 120v incandescent lamp, that may tell you if it's something more significant.