Rockford Fosgate Punch P3001

seankane · 25th October 2011, 03:16 AM

Hello everyone.

I am repairing a Punch P3001 board number PC-4714-B.

It had 47.5 VDC on the output terminals. I found Q120 and Q123 output fets shorted. I clipped them from the circuit and DC is gone.

Question I know if I replace the 2 FQA28N15 output fets the amp will work. Should I replace the corresponding FQA36P15 output fets ( Q118 and Q122 ) as well? Since this is a mono amp will it be reliable only replacing the 2 or should I replace all 4?

Perry Babin · 25th October 2011, 06:28 AM

Are you sure that both failed?

If so, it would seem like there is damage to the protection circuit and possibly to the 0.1 ohm source resistors.

I'd suggest replacing the 36Ps also.

seankane · 26th October 2011, 01:40 AM

OK I have 60 of the 28N's on order. I have the 36P's in stock. When I get them I will install them and give you an update. I thought it was strange that only the 28N's shorted and the 36P's didnt.

The source resistors metered ok, I have not tested anything in the protection circuit. I soldered 2 used 28N's to the board for testing purposes but didnt solder them to the mesha.

There was no DC and the amp produced audio. One tested good out of circuit but I think one was leaky but it still worked for testing purposes.

brandes.cm · 26th October 2011, 02:55 AM

I think Perry was saying if both 28's were bad then look into the protection. The protection circuit should shut it down if one fails shorted and possibly save the second one. Either way both 28's should be replaced.

With that era of RF amp I haven't seen to many with both the high side and low side fets fail.

25th October 2011, 03:16 AM	#1
seankane diyAudio Member Join Date: May 2010 Location: Washington State	Rockford Fosgate Punch P3001 Hello everyone. I am repairing a Punch P3001 board number PC-4714-B. It had 47.5 VDC on the output terminals. I found Q120 and Q123 output fets shorted. I clipped them from the circuit and DC is gone. Question I know if I replace the 2 FQA28N15 output fets the amp will work. Should I replace the corresponding FQA36P15 output fets ( Q118 and Q122 ) as well? Since this is a mono amp will it be reliable only replacing the 2 or should I replace all 4? __________________ Pyramid 46 Amp Power Supply----Fluke 787 Processmeter----Tektronix 465 Scope----Velleman HPS40 Scope----Soldering Iron----Desoldering Iron----Hejet HJ 500-S Heatgun----DM4070 Digital LCR Meter----Propane Torch

25th October 2011, 06:28 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Are you sure that both failed? If so, it would seem like there is damage to the protection circuit and possibly to the 0.1 ohm source resistors. I'd suggest replacing the 36Ps also. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

26th October 2011, 01:40 AM	#3
seankane diyAudio Member Join Date: May 2010 Location: Washington State	OK I have 60 of the 28N's on order. I have the 36P's in stock. When I get them I will install them and give you an update. I thought it was strange that only the 28N's shorted and the 36P's didnt. The source resistors metered ok, I have not tested anything in the protection circuit. I soldered 2 used 28N's to the board for testing purposes but didnt solder them to the mesha. There was no DC and the amp produced audio. One tested good out of circuit but I think one was leaky but it still worked for testing purposes. __________________ Pyramid 46 Amp Power Supply----Fluke 787 Processmeter----Tektronix 465 Scope----Velleman HPS40 Scope----Soldering Iron----Desoldering Iron----Hejet HJ 500-S Heatgun----DM4070 Digital LCR Meter----Propane Torch

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26th October 2011, 02:55 AM	#4
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	I think Perry was saying if both 28's were bad then look into the protection. The protection circuit should shut it down if one fails shorted and possibly save the second one. Either way both 28's should be replaced. With that era of RF amp I haven't seen to many with both the high side and low side fets fail.

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