Rockford Fosgate Punch 200x2 Old School Repair

[Mike Stephenson]

OK. All of the resistors measure between 9.7 and 10.0. I'll order some IRF540s and IRF9540s. Since I'm putting an order in, are there other components I should order. I'm not necessarily concerned as much for cost, but looking to replace anything that would be better or last longer.

 

[Perry Babin]

If the gate resistors are OK, it's likely that there are no other parts that you'll need for this repair. You will need some heatisnk compound.

 

[Mike Stephenson]

OK. I received the 540's and 9540's and installed 3 of each. I installed the circuit board in the heatsink and tightened down the bar clamps. I haven't applied heatsink compound yet, but will do so after troubleshooting, or if you recommend doing so now. I then powered up the amp and ran a 40Hz mp3 through the amp. The bias dials, gains, and bass & treble boost were all set fully counter clockwise. The head unit was set to maximum output without clipping. Here are images of the scope. I'm wondering why the speaker outputs are like a square wave instead of a smooth sine wave like the input. I tested my other good Punch 200 and it does the same thing. Is that normal?

RCA INPUT SIGNAL TO AMP

OUTPUT FROM AMP ON SPEAKER TERMINALS

 

[Perry Babin]

Because you're driving the amp to clipping.

 

[Mike Stephenson]

I didn't realize it would clip with the gains set fully CCW with a clean input signal. Is it easier to clip with higher voltage RCA outputs from a preamp or something? My Clarion EQ has 7 volt output. Anyway, thanks for the help on this. Are the next steps to put heatsink compound on and try it out on the sub's?

 

[Perry Babin]

Clean old compound
apply new compound
reassemble
set bias
try on woofers

 

[Mike Stephenson]

I set the bias pots back to where they were before the trouble started. I kept the 10A fuse inline with B+ and set the output volume from the head unit to about 1/4. When the woofers are connected the 10A fuse blows. I measured the ohms of the woofers that the amp "sees" and they read 2.8 ohms. I'm running the amp in bridged mode. After a little checking, I found that the amp puts out a sine wave across the L+ and R- terminals, but does not put out a sine wave on just the Left + & - terminals. The Right + & - terminals put out a sine wave. I guess there's still a problem on the Left channel, which is the side where the output transistors were shorted.

 

[Perry Babin]

Any time you replace parts in the power amplifier stage of one channel, you have to reset the bias.

http://www.bcae1.com/temp/ausettingbias.swf

 

[Sep78]

What was the end result?
Just happens today im looking up a fix for my Punch 200x2 amp.
Its the PC-1091 board. 10 mofets/rectifiers/transistors per side. Got some damaged by heat, trying to see if someone has schematics for this amp?
Think ive figured out the right channel.
From left to right when holding the board so the top of the heatsink is facing up, it goes
IRF9540, IRF9540, IRF9540, IRF540, IRF540, IRF540, LM337T, FEP16BT, IRFZ44, IRFZ44
When i flip the board around to view the Left channel, im looking at the opposing components)
The 3 IRF9540 are matched perfectly on the complete opposite side.
The 3 IRF540 are matched on the opposite side.
When i look at the opposing component to LM337T, it is a LM317T, the final 3 i cannot make out due to heat damage. Can anyone tell me which #'s they would be?
Would it still be the same as whats on the opposite side?
I believe FEP16BT is a rectifier, but i dont know if the opposing one would stay the same #.
The last 2 IRFZ44 should be input transisters?
They should stay the same on the other side im guessing...
Any help would be greatly appreciated!
Thankbyou kindly