Ok, so It now tries to turn on but pulls the full 2 amp limit of the power supply, at around 5 volts.
The bias pots are still full ccw.
Waveforms and voltages are as before, just not in burst form anymore.
The bias pots are still full ccw.
Waveforms and voltages are as before, just not in burst form anymore.
Nope, blows the ten amp fuse.
On the 2 amp current limited supply the power supply FETs get hot at idle and it breaks into a buzzing noise, where the drive waveform to the PS FETs stops being continuous and goes back to 45Hz bursts of 25KHz square waves. At this 2 amp limit the drive waves to the FETs are 5v pk to pk.
On the 2 amp current limited supply the power supply FETs get hot at idle and it breaks into a buzzing noise, where the drive waveform to the PS FETs stops being continuous and goes back to 45Hz bursts of 25KHz square waves. At this 2 amp limit the drive waves to the FETs are 5v pk to pk.
Did you try removing the rectifiers to see if the problem was on the PS side?
Did you use the same exact part number FETs for the power supply?
With the 2 amp supply or with the larger supply with a limiter, measure the DC voltage across the output emitter resistors. The voltage should be 0.000v with the bias pots at the minimum.
SOMEtimes, the bias is reversed. Are there any markings on the board that would indicate that the bias could be reversed (CCW is high).
When you saw the 25k square wave on the drains, was it going to ground?
Did you use the same exact part number FETs for the power supply?
With the 2 amp supply or with the larger supply with a limiter, measure the DC voltage across the output emitter resistors. The voltage should be 0.000v with the bias pots at the minimum.
SOMEtimes, the bias is reversed. Are there any markings on the board that would indicate that the bias could be reversed (CCW is high).
When you saw the 25k square wave on the drains, was it going to ground?
I was hoping it would be a simple fix, sadly not.
The Power Supply FETs are all original and pulling the rectifiers sees the amp power supply start up and oscillate properly.
I was about to go further when i noticed that the small signal transistors in the damaged channel (in which i have installed new output FETs) were getting very hot.
There are no markings on the board to indicate which way around the pots are, I will try and measure them at the extremes but without a schematic and with the SMD components on the other side it's a bit of a crap shoot. I have re-learned to appreciate sharp multimeter probes on this one... 😀
Probing with the multimeter on diode test shows that the transistors show a normal diode drop one way and leakage ( or less than OL) reading the other way, compared to the working channel.
I'm going to replace the transistors and check the surrounding resistors.
The Power Supply FETs are all original and pulling the rectifiers sees the amp power supply start up and oscillate properly.
I was about to go further when i noticed that the small signal transistors in the damaged channel (in which i have installed new output FETs) were getting very hot.
There are no markings on the board to indicate which way around the pots are, I will try and measure them at the extremes but without a schematic and with the SMD components on the other side it's a bit of a crap shoot. I have re-learned to appreciate sharp multimeter probes on this one... 😀
Probing with the multimeter on diode test shows that the transistors show a normal diode drop one way and leakage ( or less than OL) reading the other way, compared to the working channel.
I'm going to replace the transistors and check the surrounding resistors.
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