Rockford P4002

Cr@sh · 1st July 2011, 12:03 AM

Hi all, I am new to repair but not new to car audio or amplifiers. I have been going through all of Perry's links and reading as much as possible and Perry has already helped me fix my USA-50x and my 24XS crossover (Big thanks Perry!) I have had this amp lying around for a few years with a blown channel. The output on the left channel is -41v and -41.9 amps the right channel is 0 and 0 with no input signal to the amp.

It has 1 TL494c and three LM339D's I got the output of all four, I'm not sure which ones you'll need and I can take pics. Also I got the output of all the fets. I don't want to post everything as I'm sure some of it will not be needed. I was just wondering if someone can push me in the right direction?? Thanks

Perry Babin · 1st July 2011, 12:10 AM

What do you mean '-41.9 amps'?

Have you checked the output transistors in the left channel to see if any were shorted?

Cr@sh · 1st July 2011, 12:17 AM

Quote:

Originally Posted by Perry Babin

What do you mean '-41.9 amps'?

Have you checked the output transistors in the left channel to see if any were shorted?

Sorry, I set my dmm to what I though was Amps DC. One them appears to be. It's labeled 36P15. I'm sorry this amp is a little confusing on trying to figure out which is left a right because it has fets on three sides.

Perry Babin · 1st July 2011, 12:24 AM

The output transistors in the left channel will have their center legs connected to the left positive speaker terminal. It's probably the 100 series parts.

Cr@sh · 1st July 2011, 12:25 AM

This is what I use to check for shorts right?

Perry Babin · 1st July 2011, 12:27 AM

Yes.

Cr@sh · 1st July 2011, 12:39 AM

These two show -41v on all three legs

seankane · 1st July 2011, 12:54 AM

FQA28N15 and FQA36P15 they are probably both shorted, better check the the gate drive resistors and the source resistors as well. The source resistors are 0.1 ohm 2 watt. The gate drive resistors are probably 10 ohm. Dont have a schematic sitting in front of me. Remove those 2 transistors and see if the DC goes away at the terminal.

Cr@sh · 1st July 2011, 12:56 AM

OK, I had the schematics. Rockford sent them to me, I just have to find them. Thanks I'll do that!

Perry Babin · 1st July 2011, 03:43 AM

You don't check for shorted transistors with power applied.

1st July 2011, 12:03 AM	#1
Cr@sh diyAudio Member Join Date: Aug 2009 Location: Detroit	Rockford P4002 Hi all, I am new to repair but not new to car audio or amplifiers. I have been going through all of Perry's links and reading as much as possible and Perry has already helped me fix my USA-50x and my 24XS crossover (Big thanks Perry!) I have had this amp lying around for a few years with a blown channel. The output on the left channel is -41v and -41.9 amps the right channel is 0 and 0 with no input signal to the amp. It has 1 TL494c and three LM339D's I got the output of all four, I'm not sure which ones you'll need and I can take pics. Also I got the output of all the fets. I don't want to post everything as I'm sure some of it will not be needed. I was just wondering if someone can push me in the right direction?? Thanks

1st July 2011, 12:10 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What do you mean '-41.9 amps'? Have you checked the output transistors in the left channel to see if any were shorted? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

1st July 2011, 12:24 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	The output transistors in the left channel will have their center legs connected to the left positive speaker terminal. It's probably the 100 series parts. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

1st July 2011, 12:27 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Yes. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

1st July 2011, 12:54 AM	#8
seankane diyAudio Member Join Date: May 2010 Location: Washington State	FQA28N15 and FQA36P15 they are probably both shorted, better check the the gate drive resistors and the source resistors as well. The source resistors are 0.1 ohm 2 watt. The gate drive resistors are probably 10 ohm. Dont have a schematic sitting in front of me. Remove those 2 transistors and see if the DC goes away at the terminal. __________________ 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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1st July 2011, 12:56 AM	#9
Cr@sh diyAudio Member Join Date: Aug 2009 Location: Detroit	OK, I had the schematics. Rockford sent them to me, I just have to find them. Thanks I'll do that!

1st July 2011, 03:43 AM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	You don't check for shorted transistors with power applied. __________________ 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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