Just like the title says the amp lost its sub channel after battery got really low, too low to crank the car. The 1 channel works ok, and I don't use the 2 channel, but I get no sound from the sub channel. Swapped RCAs to confirm that the output is present from the head unit.
The amp is not going into protection. Red goes to green as powered on and green light stays lit. I've got +-52V on the class D rail. I've repaired a couple A/B amps but class D isn't my strong suit. Any ideas on where to start, common component failures displaying these symptoms, and any other ideas? Any help appreciated.
The amp is not going into protection. Red goes to green as powered on and green light stays lit. I've got +-52V on the class D rail. I've repaired a couple A/B amps but class D isn't my strong suit. Any ideas on where to start, common component failures displaying these symptoms, and any other ideas? Any help appreciated.
Post several pictures of the amp. One overall and several splitting the board. Once you have pics posted, I can point out some test points.
Do you have an Oscilloscope?
Do you have an Oscilloscope?
Here's the pics. In #4 transistor 704 had been pulled out years ago due to a problem with the temp sensor protect circuit. Amp isn't pushed hard and doesn't overheat so left it as is. 
Thanks for looking
EDIT: forgot to add, I have a crappy old oscilloscope that I could drag out if absolutely necessary.
Thanks for looking EDIT: forgot to add, I have a crappy old oscilloscope that I could drag out if absolutely necessary.Attachments
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From the photos you posted it appears you have blown outputs .
Coupe be the camera angle but it looks like a source resistor is burnt which mean the output has failed
Coupe be the camera angle but it looks like a source resistor is burnt which mean the output has failed
Must be the picture, those all measure out a smidge under 1 ohm. They're also for the two A/B sections of the amp that are working.
I did read through all the search results for this amp. There tends to be a lot of issues with the class D section of this amp. Mine seems unique among them. Amp not in protection with ~52V +- on the D rail and 30V+- on the A/B rail. Working A/B with no output from the class D section, no hum, nothing.
Well amplifiers typically lose the output transistors. If you have a scope, check out the gate drive or connections into the output power transistor gate drive, to see if the PWM has an active output with an input audio signal. Otherwise if it has power to the supply rails and is not in protection, mode, I would be looking at the output power transistors.
Post DC voltages for the points I show in the attachment.
If you have a scope check the waveforms at the sub out pin on preamp board, Also Pins 3,4,11 on U909-LM361. The Class D output drive should be present at the Gates and Drain of the IFR640 and IRF9640 sub output mosfets.
If you have a scope check the waveforms at the sub out pin on preamp board, Also Pins 3,4,11 on U909-LM361. The Class D output drive should be present at the Gates and Drain of the IFR640 and IRF9640 sub output mosfets.
You measured the sub output mosfets? The Mosfets are Q210,211,213,214-IRF9640's and Q216,217-IRF640's. They should all read high ohms and between the outside legs will read 50K ohm. If they are less than 1 ohm the amp will protect itself.
Are there any voltage regulators for the D section that could have failed? Have you checked regulated voltage? I'm not familiar with this amp but I've seen this happen in many others.
From the diagram PapaZBill posted:
The header pins on the input board have + and - 12v and the v.c pin read 10.3V
The header of the class D board have + and - 12v on the respective pins. Simk has +5.6v
The IC of the class D board (numbered 1 at top left and 2 top right and so on going down)
pin 1 +12V, pin 2 +2.8V, pin 4 +2.8V, pin 8 +0.4V, pin 10 -1.8V, and pin 14 2.8V, all others 0V DC
The DC read across the outer leads of the sub outputs is 4.0V for the ones fed from the positive rail and 3.9V for the negative rail.
The header pins on the input board have + and - 12v and the v.c pin read 10.3V
The header of the class D board have + and - 12v on the respective pins. Simk has +5.6v
The IC of the class D board (numbered 1 at top left and 2 top right and so on going down)
pin 1 +12V, pin 2 +2.8V, pin 4 +2.8V, pin 8 +0.4V, pin 10 -1.8V, and pin 14 2.8V, all others 0V DC
The DC read across the outer leads of the sub outputs is 4.0V for the ones fed from the positive rail and 3.9V for the negative rail.
Okay, So what I'm seeing is the Class D board and preamp board have the proper voltages and you are seeing Drive at the sub channel mosfets.
So the audio is being interrupted somewhere between the RCA's and the Class D board.
You can use your voltmeter to signal trace with AC volts. Start with the Out pin on the preamp header, using a 40hz sine wave if available. If you need one you can download from Kicker.com on on the support page. There will be other sources, Perry Babin for instances.
So the audio is being interrupted somewhere between the RCA's and the Class D board.
You can use your voltmeter to signal trace with AC volts. Start with the Out pin on the preamp header, using a 40hz sine wave if available. If you need one you can download from Kicker.com on on the support page. There will be other sources, Perry Babin for instances.
Great! Thanks. If its likely that the class D amp is ok I should be able to trace the signal path. If I run into any roadblocks I'll post them up.
Ok, so I had a chance to play with this again this morning. It appears my signal path is ok and the problem is somewhere in the output. I noticed that C211 was warm and a bit swollen so I subbed in another close value 100V cap. It popped pretty spectacularly once I turned up the gain. Before I go poking and prodding, I thought I'd run that past the experts and see what you guys think.
Another thing I noticed is that I get a bit of static-y hum similar to the power supply transformers near the output that correlates to the volume gain of the sub input. It doesn't seem like its from the large output torroid inductor, but honestly I'm not sure. It almost seems like its coming from under the preamp board but there isn't a lot under there aside from a smaller inductor and a few large blue caps.
Another thing I noticed is that I get a bit of static-y hum similar to the power supply transformers near the output that correlates to the volume gain of the sub input. It doesn't seem like its from the large output torroid inductor, but honestly I'm not sure. It almost seems like its coming from under the preamp board but there isn't a lot under there aside from a smaller inductor and a few large blue caps.