Rockford Fosgate P8004

mike49504 · 8th June 2010, 06:02 PM

I have this amp in for repair. Ive never seen an amp do this before.

The problem with this amp is when u hook it up it will play fine until u shut the car off and then turn it back on.

For example say your running this amp in your car everything is working like it should . Then you stop at a store shut the car off go in get what u need come back out start the car up And the amp will power up but will have no output.

The only way to get the amp back working again is to unplug the rca's shut the head unit off then turn the head unit back on and plug the rca's back in then the amp will work again til u shut the car off.

If this makes any sense.

Wondering what the problem might be and where to begin to check?

Perry Babin · 8th June 2010, 06:40 PM

Can you duplicate the problem on the bench?

mike49504 · 8th June 2010, 06:51 PM

Yes i can get to do it it on the bench as well. I opened it up and found it had a defective output. Would this cause the problem or is ther something more possibly wrong?

Perry Babin · 8th June 2010, 07:29 PM

Unless the output was leaking (not completely shorted) or there was a fault in the protection circuit, I don't see how the output could cause it. Repair the channel to see if that solves your problem.

mike49504 · 10th June 2010, 01:53 AM

Perry,

Somemore checking into this amp i noticed some resistors and transistors that are badly burnt to the point i can read them. Wondering if you know what values i need?

R136:
R139:
R133:
R192
R193
Q192
Q193

Perry Babin · 10th June 2010, 02:20 AM

I don't have anything on that amp. Try to get the schematic diagram from Rockford.

speye · 14th June 2010, 03:24 AM

just had one of em amps opened this morning ...was checking it 4 a friend...wish i had seen this b4 ..could have hepled.

mike49504 · 28th June 2010, 07:22 PM

Im working on this amp again. They are using 20 ohm resistors with 1% tolerance.

Closest thing i have right now is a 22 ohm resistor Wondering will the 22 ohm work?

Perry Babin · 28th June 2010, 08:19 PM

For the audio drivers?

They should work. You could use them for testing and if there are no other problems, you could order the correct ones.

mike49504 · 30th June 2010, 04:49 PM

Im still repairing this amp. In one section of the amp the resistors and transistors burnt when they burnt they also took the some of the pads along with it. I can figure out where some of the traces went .

1 Side of R133 connects to Q105 in this amp I cannot tell where the other sides of R133 connects since the board is damaged.

Would the schematic tell me where it connects or not?

8th June 2010, 06:02 PM	#1
mike49504 diyAudio Member Join Date: Sep 2006	Rockford Fosgate P8004 I have this amp in for repair. Ive never seen an amp do this before. The problem with this amp is when u hook it up it will play fine until u shut the car off and then turn it back on. For example say your running this amp in your car everything is working like it should . Then you stop at a store shut the car off go in get what u need come back out start the car up And the amp will power up but will have no output. The only way to get the amp back working again is to unplug the rca's shut the head unit off then turn the head unit back on and plug the rca's back in then the amp will work again til u shut the car off. If this makes any sense. Wondering what the problem might be and where to begin to check?

8th June 2010, 06:40 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Can you duplicate the problem on the bench? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

8th June 2010, 07:29 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Unless the output was leaking (not completely shorted) or there was a fault in the protection circuit, I don't see how the output could cause it. Repair the channel to see if that solves your problem. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

10th June 2010, 02:20 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	I don't have anything on that amp. Try to get the schematic diagram from Rockford. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

28th June 2010, 08:19 PM	#9
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	For the audio drivers? They should work. You could use them for testing and if there are no other problems, you could order the correct ones. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links


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8th June 2010, 06:51 PM	#3
mike49504 diyAudio Member Join Date: Sep 2006	Yes i can get to do it it on the bench as well. I opened it up and found it had a defective output. Would this cause the problem or is ther something more possibly wrong?

10th June 2010, 01:53 AM	#5
mike49504 diyAudio Member Join Date: Sep 2006	Perry, Somemore checking into this amp i noticed some resistors and transistors that are badly burnt to the point i can read them. Wondering if you know what values i need? R136: R139: R133: R192 R193 Q192 Q193

14th June 2010, 03:24 AM	#7
speye diyAudio Member Join Date: May 2005 Location: house	just had one of em amps opened this morning ...was checking it 4 a friend...wish i had seen this b4 ..could have hepled.

28th June 2010, 07:22 PM	#8
mike49504 diyAudio Member Join Date: Sep 2006	Im working on this amp again. They are using 20 ohm resistors with 1% tolerance. Closest thing i have right now is a 22 ohm resistor Wondering will the 22 ohm work?

30th June 2010, 04:49 PM	#10
mike49504 diyAudio Member Join Date: Sep 2006	Im still repairing this amp. In one section of the amp the resistors and transistors burnt when they burnt they also took the some of the pads along with it. I can figure out where some of the traces went . 1 Side of R133 connects to Q105 in this amp I cannot tell where the other sides of R133 connects since the board is damaged. Would the schematic tell me where it connects or not?

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