Assuming that you've checked all of the outputs and none are shorted, and it does not draw excessive current when no load is connected to the speaker outputs...
Post the DC voltage on all of the pins of U17 (should be an LM6171).
Do this with the amp powered up and no speaker load.
As a side note, this amp retains significant energy in the caps. They must be discharged before you do any work on the amp. This needs to be done every time the amp is powered down. If you have a high power dummy load, short it across the large red and black (twisted together) wires (after the amp is switched off).
Post the DC voltage on all of the pins of U17 (should be an LM6171).
Do this with the amp powered up and no speaker load.
As a side note, this amp retains significant energy in the caps. They must be discharged before you do any work on the amp. This needs to be done every time the amp is powered down. If you have a high power dummy load, short it across the large red and black (twisted together) wires (after the amp is switched off).
If all of the 6215s are blown, you must also replace all of the 3415s.
Check the gate resistors for all of the output FETs. They often open with no visible signs of being defective.
On the MIC4420 drivers, you should not have any low resistance (near 0 ohms) between any of the pins except 2 and 4. Check both drivers. You may need to do this after you remove the blown FETs to prevent the shorted FETs from giving false readings. If the driver has shorted, there may be other damage that can be difficult to find. If the drivers survived, it's likely that the only damage is to the outputs and possibly the gate resistors.
Check the gate resistors for all of the output FETs. They often open with no visible signs of being defective.
On the MIC4420 drivers, you should not have any low resistance (near 0 ohms) between any of the pins except 2 and 4. Check both drivers. You may need to do this after you remove the blown FETs to prevent the shorted FETs from giving false readings. If the driver has shorted, there may be other damage that can be difficult to find. If the drivers survived, it's likely that the only damage is to the outputs and possibly the gate resistors.
The shield ground should have no direct connection to chassis ground unless there is a defect like a shorted diode.
You said it's doing the same thing but the top of the post indicated constant DC (pulling the woofer in). Are you sure it's the same problem?
Is the problem the same whether in the vehicle or on the test bench?
You said it's doing the same thing but the top of the post indicated constant DC (pulling the woofer in). Are you sure it's the same problem?
Is the problem the same whether in the vehicle or on the test bench?
i powerd up the amp on the bench and looked at the sub to see what the guy was talking about with the gain all the way down u can hear a lil distorion on the sub when u start turning the gain up lil by lil the distorion goes away but u can watch the sub flutter move up and down i checked the rca grounds and replaced them due to the fact the rca ground where broke off the board so thats fixed the i was doing a visual on other parts and came across the cap in the power supply thr pf2475-nd 4.7 mf 250 volt with a broken lead on it so i replaced that powerd up the amp and doing same thing the speaker flutters a lil and the lm317 and lm337 get hot really quickly but the amp still plays but with the speaker flutter prob wondering where i might go from here what do i check?
also when the amp is powerd up dont know if this is normal or not amp powerd up no signal pluged into it took meter leads and touched them on speakers outputs the dc voltage read 135.1 and with the meter leads reversed -135.1 i watched the sub connected to it and it flutters a lil bit back and fourth wondering what this might be form?
There are two regulators (317/337) for the preamp section and 4 regulators for the amplifier section (all in heatsinks). Do all of them get really hot really fast? If only one or two are getting too hot, that could lead you to the problem. They run hot but if they get too hot to touch in a minute or less, there is a problem.
While the amp is on and powered up, measure the DC voltage across the large black and red twisted wires (black lead on black wire, red lead on red wire). Don't allow the leads to short to anything while doing this.
If you have 135 volts of DC across the speaker terminals, when a speaker is connected, the speaker should pull in or push out. Either way, I'd expect the speaker to fail within seconds. Are you sure it wasn't 135 millivolts instead of 135 volts?
While the amp is on and powered up, measure the DC voltage across the large black and red twisted wires (black lead on black wire, red lead on red wire). Don't allow the leads to short to anything while doing this.
If you have 135 volts of DC across the speaker terminals, when a speaker is connected, the speaker should pull in or push out. Either way, I'd expect the speaker to fail within seconds. Are you sure it wasn't 135 millivolts instead of 135 volts?
In this amp, half of the outputs are rail switchers. The other half produce the audio output. If only one half are defective, that's all you need to replace.
Check the driver IC (MIC4420). If the first pin is shorted to any others, it's defective. If you have to pull it, heat the mounting pin while pulling the sink away from the board. After the sink is removed, apply enough solder to the pins (on the bottom of the board) to allow you to heat all of them if you lay your iron down between the pins (the solder on all pins must bridge to the iron). When all are hot, the IC will pull cleanly from the board. If I'm not mistaken, you should read something on the order of mega ohms from pin one to any of the other pins.
Tantalum caps can fail but rarely do in modern electronics. They are sensitive to heat and reverse polarity so you need to be careful of those when working with them. The failure mode is almost always shorting or leaking (electrically).
If the outputs are defective, it can cause all sorts of problems.
The regs are internally protected and rarely fail. They were likely getting hot due to a defective driver (MIC4420).
Check the driver IC (MIC4420). If the first pin is shorted to any others, it's defective. If you have to pull it, heat the mounting pin while pulling the sink away from the board. After the sink is removed, apply enough solder to the pins (on the bottom of the board) to allow you to heat all of them if you lay your iron down between the pins (the solder on all pins must bridge to the iron). When all are hot, the IC will pull cleanly from the board. If I'm not mistaken, you should read something on the order of mega ohms from pin one to any of the other pins.
Tantalum caps can fail but rarely do in modern electronics. They are sensitive to heat and reverse polarity so you need to be careful of those when working with them. The failure mode is almost always shorting or leaking (electrically).
If the outputs are defective, it can cause all sorts of problems.
The regs are internally protected and rarely fail. They were likely getting hot due to a defective driver (MIC4420).
i put my meter leads on the black and red twisted wires hv+ red lead hv- black lead with amp powerd up no speakers or signal connected and my meter read 92.8 volts is this normal? wondering what else i check out to figure out why the speaker still flutters and i checked the dc voltage on speaker outputs meter read 0.1 volts
Without a scope, this is going to be hard to find.
Have you checked for open traces. There's one between the transformer and the rail caps that open sometimes.
If this amp uses the board I think it does, check all 'op-amps' EXCEPT U5, U21, U18, U8, and U11. If the op-amps are good, the voltage on the inverting input should match those on the non-inverting input. Look up the datasheets for the op-amps to determine the pin-out configuration. Some of the op-amps are singles and some are duals. Don't let you meter leads slip when probing. The voltage should match within ~0.005v DC. Do this with no input signal. For consistency, place the black lead on the inverting input.
If you find one that has more than 0.005v between the inputs, post the voltage for both inputs and the output voltage. For these three voltages, use the chassis ground for the reference (black lead on chassis ground).
Have you checked for open traces. There's one between the transformer and the rail caps that open sometimes.
If this amp uses the board I think it does, check all 'op-amps' EXCEPT U5, U21, U18, U8, and U11. If the op-amps are good, the voltage on the inverting input should match those on the non-inverting input. Look up the datasheets for the op-amps to determine the pin-out configuration. Some of the op-amps are singles and some are duals. Don't let you meter leads slip when probing. The voltage should match within ~0.005v DC. Do this with no input signal. For consistency, place the black lead on the inverting input.
If you find one that has more than 0.005v between the inputs, post the voltage for both inputs and the output voltage. For these three voltages, use the chassis ground for the reference (black lead on chassis ground).
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