Rockford Fosgate Punch 500S

seankane · 8th June 2011, 12:34 AM

Hello everyone.

I recieved this Punch 500S in for repair, board number PC-3082-C.

The amp was pulsing from 0vdc to 60vdc on the power supply. Now at first thought its like someone turned the bias pots up as a gain as I see alot.

One of the channels had pulsing DC on it. I thought someone had cranked the bias pot and blew some outputs. I removed the outputs from that channel and re-powered amp with same result.

I thought maybe a bad bias pot, so I removed the pot and re-powered amp with same result.

I had this problem with a 200ix Perry helped me with and it was some bad smd resistors and smd bjt's but am unsure if this could be it or it is something else. I dont like replacing uneeded parts as it is time consuming and costly to me.

I was wondering if someone could point me in the right direction, any help would be greatly appreciated...........Thanks again.

Perry Babin · 8th June 2011, 03:56 PM

100 or 200 series parts?

seankane · 8th June 2011, 09:21 PM

200 series parts.

Perry Babin · 8th June 2011, 10:07 PM

What happens if you lift Q209 and Q211?

seankane · 8th June 2011, 10:41 PM

Same issue pulsing from 0vdc to 60vdc on the power supply.

Q209 and Q211 are removed.

All output fets in that channels are removed.

Bias pot is installed.

Perry Babin · 9th June 2011, 02:40 AM

60v DC?

Do you mean 60v on the speaker terminals or do you mean 60 amps on the 12v power supply?

seankane · 9th June 2011, 02:42 AM

60 amps on the power supply sorry. The most I saw on the speaker terminal was 30 something vdc jumps all over the place as it pulses.

Perry Babin · 9th June 2011, 02:45 AM

With no outputs?

Do you read any voltage across any of the 0.1 ohm source resistors (check every one)?

Are there any solder bridges between the pads for the outputs?

seankane · 9th June 2011, 03:00 AM

Quote:

Originally Posted by Perry Babin

With no outputs?

Do you read any voltage across any of the 0.1 ohm source resistors (check every one)?

Are there any solder bridges between the pads for the outputs?

Im sorry should have been more clear.

The DC on the speaker bridging terminal was with the outputs installed, and it went up and down with the pulsing of the amp on the power supply amp meter.

I did not check for DC on the emitter esistors with the output fets installed but with them uninstalled it is 0.000vdc on all of them.

There are no solder bridges.

The amp is pulsing just like it would if the bias pot was fully cranked clockwise.

The opposite channel did not have DC pulsing on the bridging terminal.

I am afraid to leave it on to long pulsing dont want to blow the power supply.

Perry Babin · 9th June 2011, 03:08 AM

Do you still have excessive current draw without the outputs in the circuit?

You need to insert a current limiting resistor in the B+ line. If you have big dummy loads, you can use those. 1.5-2 ohms is a good value. It protects the transistors (if they're clamped down) and allows enough current to find many faults.

8th June 2011, 12:34 AM	#1
seankane diyAudio Member Join Date: May 2010 Location: Washington State	Rockford Fosgate Punch 500S Hello everyone. I recieved this Punch 500S in for repair, board number PC-3082-C. The amp was pulsing from 0vdc to 60vdc on the power supply. Now at first thought its like someone turned the bias pots up as a gain as I see alot. One of the channels had pulsing DC on it. I thought someone had cranked the bias pot and blew some outputs. I removed the outputs from that channel and re-powered amp with same result. I thought maybe a bad bias pot, so I removed the pot and re-powered amp with same result. I had this problem with a 200ix Perry helped me with and it was some bad smd resistors and smd bjt's but am unsure if this could be it or it is something else. I dont like replacing uneeded parts as it is time consuming and costly to me. I was wondering if someone could point me in the right direction, any help would be greatly appreciated...........Thanks again. __________________ 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

8th June 2011, 03:56 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	100 or 200 series parts? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

8th June 2011, 09:21 PM	#3
seankane diyAudio Member Join Date: May 2010 Location: Washington State	200 series parts. __________________ 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

8th June 2011, 10:07 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What happens if you lift Q209 and Q211? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

8th June 2011, 10:41 PM	#5
seankane diyAudio Member Join Date: May 2010 Location: Washington State	Same issue pulsing from 0vdc to 60vdc on the power supply. Q209 and Q211 are removed. All output fets in that channels are removed. Bias pot is installed. __________________ 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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9th June 2011, 02:40 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	60v DC? Do you mean 60v on the speaker terminals or do you mean 60 amps on the 12v power supply? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

9th June 2011, 02:42 AM	#7
seankane diyAudio Member Join Date: May 2010 Location: Washington State	60 amps on the power supply sorry. The most I saw on the speaker terminal was 30 something vdc jumps all over the place as it pulses. __________________ 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

9th June 2011, 02:45 AM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	With no outputs? Do you read any voltage across any of the 0.1 ohm source resistors (check every one)? Are there any solder bridges between the pads for the outputs? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

9th June 2011, 03:08 AM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Do you still have excessive current draw without the outputs in the circuit? You need to insert a current limiting resistor in the B+ line. If you have big dummy loads, you can use those. 1.5-2 ohms is a good value. It protects the transistors (if they're clamped down) and allows enough current to find many faults. __________________ 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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