The tranformer short is fixed!🙂 I did as described in the previous posts. First I reattached R118 between the grounds. I had to work in the dark as it was a tiny spark from the bottom side of the board near pin 4.
I gently moved a wire or two away to get to source of the spark. The enamel was visibly marred. I stuffed a piece of mica insulator between the wires and used some potting coumpound (high temp Dow Corning RTV) to keep things in place. No more short.
I hooked it up in the car since it would have a load on it and a fused B+. Upon connecting the fuse under the hood it arked once. The amp won't power on now. I have another amp electrically parallel and that is working fine. It is seeing 12V power, gnd, and remote but not powering up. I haven't had a chance to do any diagnostics yet but any ideas an where to look would be helpful.
Thanks and thanks for all the help thus far. I have been learning a ton of cool stuff.
I gently moved a wire or two away to get to source of the spark. The enamel was visibly marred. I stuffed a piece of mica insulator between the wires and used some potting coumpound (high temp Dow Corning RTV) to keep things in place. No more short.
I hooked it up in the car since it would have a load on it and a fused B+. Upon connecting the fuse under the hood it arked once. The amp won't power on now. I have another amp electrically parallel and that is working fine. It is seeing 12V power, gnd, and remote but not powering up. I haven't had a chance to do any diagnostics yet but any ideas an where to look would be helpful.
Thanks and thanks for all the help thus far. I have been learning a ton of cool stuff.
IF you have voltage at the amp, you'll need to start with the DC voltage on all pins of the power supply driver IC.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
No. At least I dont think so. Both sides are in the mV range. However I had a mishap with a FET. A small strand of wire from my B+ or grd wire fell across a FET and toasted it. I have a new one on the way. When it arrives I will check it again. I removed the bad one altogether so I assume that nothing is working right as it is now. Assuming that D19 doesn't have 10+ V what might I be looking for?
D19 is directly connected to the remote terminal. If you don't have voltage there, the amp probably has no remote voltage at the terminal.
OK, the FET is replaced and the amp is back to where I was before. The pins on the drive IC read the same as previously stated. D19 has 12.3V upstream and 11.5V downstream so the remote is OK to that point There is 0.75V at Q69 just after (3.3K R153C) from the remote diode.
Rail voltage is about 30mV on rail+ and -300 mV on rail-. Idle current is 18mA as measured by inserting the meter inline of B+.
Is there something going on with the driver? Should pin 11 and 14 have some duty cycle that should be measurable? Is there a way to check the transistors between the FETs and the driver?
Thanks again.
Rail voltage is about 30mV on rail+ and -300 mV on rail-. Idle current is 18mA as measured by inserting the meter inline of B+.
Is there something going on with the driver? Should pin 11 and 14 have some duty cycle that should be measurable? Is there a way to check the transistors between the FETs and the driver?
Thanks again.
With your black probe on one of the non-bridging speaker terminals, do you still read rail voltage that's only a few volts (or less)?
The rail+ was reading about -15mV and rail- about 30mV with ground reference on the non-bridging speaker terminals.
OK, post the DC voltage on all of the pins of the 3524.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 1: 2mV
Pin 2: 2.57V
Pin 3: 230mV
Pin 4: 0
Pin 5: 0
Pin 6: 3.33V
Pin 7: 2.5V
Pin 8: 0
Pin 9: 200mV
Pin 10: 1.2mV
Pin 11: 0
Pin 12: 11.57V
Pin 13: 11.57V
Pin 14: 0
Pin 15: 11.57
Pin 16:5V
Reference12.3V
Pin 2: 2.57V
Pin 3: 230mV
Pin 4: 0
Pin 5: 0
Pin 6: 3.33V
Pin 7: 2.5V
Pin 8: 0
Pin 9: 200mV
Pin 10: 1.2mV
Pin 11: 0
Pin 12: 11.57V
Pin 13: 11.57V
Pin 14: 0
Pin 15: 11.57
Pin 16:5V
Reference12.3V
D18 is open. When I removed it I get rail + of 25v and rail - of -25v. I will replace it and go from there. I have a 10 amp fuse on B+ but I was quick about the measurement. Should I expect any other issues now since I will most likely have to order a MBR 150 9747?
THANKS AGAIN.
THANKS AGAIN.
Also for my learning what is going on here? Why or how did an open diode on the protection ciruit limit rail voltage? Thanks.
If the diode was open, it could not have caused the amp to shut down. Are you sure that you don't mean 'shorted'?
That is what I thought as well but there is no continuity either way across D18 with it on or off the board. I will double check though. Either way I will need to replace it.
I got the replacement D18 diode (MBR150) in. Once again I have no or little rail voltage. I am thinking that either the IC is bad or more likely something in the protection circuit is faulty. Any ideas?
I am not sure how to test the Schottky diodes - MBR150. Brand new out of the package they measure open. Are they gated below a min current or voltage?
I am not sure how to test the Schottky diodes - MBR150. Brand new out of the package they measure open. Are they gated below a min current or voltage?
They are tested like any other diode but you can expect them to have a lower forward voltage than normal diodes.
Remove C57. Does that make a difference. Leave the diode in the circuit.
Remove C57. Does that make a difference. Leave the diode in the circuit.
- Status
- Not open for further replies.