Rockford Fosgate Punch 45HD no vcc on pin 12 of TL594CD

[Kip McGee]

I decided it was punch45 day. I broke out some old 45s and I am now stuck
on a PUNCH45hd .I have no schematic and the B+ wire was black and the
ground wire was red. I am assuming it was hooked up backwards, It was DOA
I have ran it down as far possible with my knowledge of amplifiers. I know there
are 0 volts on pin 12 of TL594cd the chip isn't turning on. I am assuming there is
something wrong with the other IC on the riser board LM339D .I was hoping someone
could point me the right direction..I do have a scope If I need it. THANKS

[Perry Babin]

Do you have DC voltage on pin 12 of the driver board? It should get voltage via D11. D11 is connected to the remote turn-on terminal.

[Kip McGee]

Upon closer inspection it looks like the riser board labeled HB8 has quite a bit of buildup
on the terminals that connect it to the main board, HB8 contains both TL594cd and LM339D
in the power supply section. I am going to re-flow the solder where it looks bad.
D11 or CR11 has 12 volts on it when I hook up the remote turn on.
I am not sure what you mean by asking If there is DC voltage on pin 12 of the driver board,There are
6 riser boards ,They all look like some sort of driver board to me,,,??
HB1 located directly in front of the RCA inputs I am guessing a pre amplifier
HB3,HB6,HB7 and HB4 look like drivers to the Right and Left Channels
then there is HB8 the one that drives the power supply BUZ11s
THANKS

[Perry Babin]

The driver board I was referring to was the power supply driver board (the one with the TL594).

Yes. CR11. You should be able to follow the trace from CR11 to pin 12 of the power supply driver board.

[Kip McGee]

I thought I had already answered this ,The punch45HD is back to working.It had an open trace on the driver board .I found it with my ohm meter and Perrys help.
I have another Punch 45 that isnt acting right . It powers on both chanels are weak where should I start .Its almost as if the PS filter caps are weak .I checked them out of circit measured less than 900uf .Most check over 1000uf ..Should I replace them.

[Perry Babin]

Do you have an oscilloscope?

[Kip McGee]

yes Perry ,I have an Oscilloscope.I also have a signal generator.However I am a little out of practice with the scope.

[Perry Babin]

Drive a signal into the amp (music or a low frequency sine wave). Do you have clean audio out on pins 5 and 27 of the preamp board (behind the RCA jacks)?

Is the output at the speaker terminals clean or is it distorted?

Set the scope to 2v/div and 2mS/div as a starting point.

[Kip McGee]

Hey..From the answer you just gave me I am assuming this is the test
that I would do on the PUNCH45HD (HD) the first amp that you helped me with is now pumping out bass in someones trunk.
The question I was asking was on a different amp The Punch 45 (without HD and without the fuses)The punch45 1st generation
I found two 35volt 1000uf caps at radio shack Iam gonna go ahead and replace the two caps. The amp sounded the same even with the old ones taken out of the circuit. I will let everyone know If this is the repair for this amp.
I will give a little history of the amp .When I first looked at the amp the heat sink wasn't shiny black
like it is should be it had changed color .It had a touch of a bronze tint to the heat sinking(Someone drove it very hot for a long time). The two power supply transistors were shorted as well as both output transistors in the orange and black channel. I replaced these with as close a match as I had on hand. I replaced the MTP3055A the N mosfet with a BUZ11A and the TP12PO5 with RFP12P10 a P mosfet from the old school mosfet 650.The power supply NPNs are original D44VH4 from GE
The Amp would turn on and play but was very distorted on both channels even at low power. So I looked closer and could see that one of the power supply caps was bulging on the + side. I unsolder both caps from the circuit and did a couple of capacitance test both caps measured around 900uf with a AMPROBE 33XR-A .I got a phone call and came back forgetting I had unsoldered the caps. I fired the amp back up and listened to it again, it sounded the same with or without the power supply caps.
I am replacing the caps but I do not really think this will fix the problem.I will report back what happens.

[Kip McGee]

Now after replacing the caps .The yellow and brown channel is clean at low volume driving my mids and highs ..The distortion is in the channel that I replaced the two outputs in . Perhaps I need a lesson in biasing the two new output transistors.I do not know how to find the proper quiescent current or set it.Am I on the right track here?
Do you think I used the right replacement parts?