This amp came to me missing many components.
U18, U21, U11, U13, RCA inputs, all switches and pots, and the protect led were all missing.
Someone also replaced all the out put FET's.
Someone also replaced all power supply FET's with FQP 85N06 with 10 ohm gates (not sure about this sub) and all rectifiers were replaced as well.
All power supply FET's test good and the power supply has good drive signal.
The amp is making regulated and rail voltage.
I replaced all missing components.
All output FET's and power supply FET's test OK.
The amp powers up but the protect LED does not light up on initial start then shut off, and U11 is getting extremely hot
The class D section is not turning on like its in protect but the protect LED is not lit.
Does U18 carrier signal latch to U21? I can't seem to figure out why the class D section is not turning on. Any suggestions?
U18, U21, U11, U13, RCA inputs, all switches and pots, and the protect led were all missing.
Someone also replaced all the out put FET's.
Someone also replaced all power supply FET's with FQP 85N06 with 10 ohm gates (not sure about this sub) and all rectifiers were replaced as well.
All power supply FET's test good and the power supply has good drive signal.
The amp is making regulated and rail voltage.
I replaced all missing components.
All output FET's and power supply FET's test OK.
The amp powers up but the protect LED does not light up on initial start then shut off, and U11 is getting extremely hot
The class D section is not turning on like its in protect but the protect LED is not lit.
Does U18 carrier signal latch to U21? I can't seem to figure out why the class D section is not turning on. Any suggestions?
What's the DC voltage on the emitter of Q120?
Do you have a good triangle waveform on pin 7 of U11?
Is the protect LED good?
Do you have a good triangle waveform on pin 7 of U11?
Is the protect LED good?
Q120 emitter is: -9.86 vdc
U11 has perfect triangle waveform on pin 7 but still very hot.
The LED is brand new but I guess it could be defective.
U11 has perfect triangle waveform on pin 7 but still very hot.
The LED is brand new but I guess it could be defective.
Even new, U11 could be defective.
Could the LED be in in reverse?
Do you see the delay on the output of U21 when you power up the amp?
Triangle waveform on U5, pin 3?
DCv on all terminals of U5?
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Could the LED be in in reverse?
Do you see the delay on the output of U21 when you power up the amp?
Triangle waveform on U5, pin 3?
DCv on all terminals of U5?
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
U5 reads as follows:
Pin 1: -9.86
Pin 2: -8.20
Pin 3: 0.098
Pin 4: -9.86
Pin 5: 0.000
Pin 6: -8.98
Pin 7: 9.93
Pin 8: -9.86
U5 pin 3 has perfect triangle waveform
U21 does not have delay, instant DC on both output pins.
LED was installed per looking at another amps installed configuration, it could be defective.
U11 is new and was my last new part, but I have used ones laying around, could swap it?
Pin 1: -9.86
Pin 2: -8.20
Pin 3: 0.098
Pin 4: -9.86
Pin 5: 0.000
Pin 6: -8.98
Pin 7: 9.93
Pin 8: -9.86
U5 pin 3 has perfect triangle waveform
U21 does not have delay, instant DC on both output pins.
LED was installed per looking at another amps installed configuration, it could be defective.
U11 is new and was my last new part, but I have used ones laying around, could swap it?
U8 reads as follows:
Pin 2: 1.083
Pin 3: -2.912
Pin 6: -5.46
Voltage across R122 is 0.000
You asked for R122 twice?
Pin 2: 1.083
Pin 3: -2.912
Pin 6: -5.46
Voltage across R122 is 0.000
You asked for R122 twice?
The silk screen is really hard to read on this board. Is R128 connected to pin 3 of U8?
If so it has 2.789 vdc across R128
I'll replace U5
If so it has 2.789 vdc across R128
I'll replace U5
Well... There should be no voltage across that resistor.
That would mean that U8 would be defective. I'd try replacing U8 first.
That would mean that U8 would be defective. I'd try replacing U8 first.
Replaced U8 and this brought voltage across R128 to 0.000
U5 was still higher on pin 3 than pin 2 and negative.
Changed U5 and this brought pins 2 and 3 to near 0 vdc but still reading negative.
Q104 blew, not sure why lol. Removed it from circuit for now.
Seems the class D section is now on but no protect led light.
No dc on output pins so tried to hook up a speaker and the amp went crazy and made horrible sounds through speaker and has no audio output.
U5 was still higher on pin 3 than pin 2 and negative.
Changed U5 and this brought pins 2 and 3 to near 0 vdc but still reading negative.
Q104 blew, not sure why lol. Removed it from circuit for now.
Seems the class D section is now on but no protect led light.
No dc on output pins so tried to hook up a speaker and the amp went crazy and made horrible sounds through speaker and has no audio output.
U8 was loading U11.
V on 2, 3 and 6 of U5?
Do you get rail-rail oscillation?
DCv on all terminals of U21?
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
V on 2, 3 and 6 of U5?
Do you get rail-rail oscillation?
DCv on all terminals of U21?
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
U5 reads as follows:
Pin 2: -0.013
Pin 3: -0.094
Pin 6: 0.324
U21 reads as follows:
Pin 1: -8.47
Pin 2: 0.016
Pin 3: -8.99
Pin 4: -9.85
Pin 5: 5.02
Pin 6: 8.25
Pin 7: -8.56
Pin 8: 9.92
I just burned my scope lead in half on my soldering iron lol, I'll have to find another before I can see Oscillation
Pin 2: -0.013
Pin 3: -0.094
Pin 6: 0.324
U21 reads as follows:
Pin 1: -8.47
Pin 2: 0.016
Pin 3: -8.99
Pin 4: -9.85
Pin 5: 5.02
Pin 6: 8.25
Pin 7: -8.56
Pin 8: 9.92
I just burned my scope lead in half on my soldering iron lol, I'll have to find another before I can see Oscillation
C51 should start at 0v when remote is applied and charge up. When it passes 5v (a few seconds), the output should swing from +8v to -8v.
The cheap ($5) probes work well enough. Keep a few backups in stock.
U5 looks OK. There is always some input offset. It's when they are significantly different that you can use the voltage for troubleshooting.
The cheap ($5) probes work well enough. Keep a few backups in stock.
U5 looks OK. There is always some input offset. It's when they are significantly different that you can use the voltage for troubleshooting.
U21 pin 7 is working as it should. Maybe I'm using the wrong LED.
The one I'm using is used for the power on light for the older DSM amps.
The one I'm using is used for the power on light for the older DSM amps.