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

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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
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
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.
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)
An externally hosted image should be here but it was not working when we last tested it.
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.
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?
Does your 12v power supply have an amp meter?

The bronze tint is due to the dye fading. Many people blame it on heat but I doubt that's the cause. If it were, the area under the transistors would be the lightest and they're generally the darkest. If that area didn't fade due to a lack of oxygen, the area just around the outputs and power supply transistors would be faded more than any other area and (from what I've seen), that's not the case.

I'd think the replacement outputs would work. Are you 100% sure they're not defective?

You could swap the outputs from one channel to the other to see if the distortion follows the outputs.

While it's possible to have the outputs underbiased, it's unlikely that you could have them so underbiased that it would cause significant distortion.
I Had it underbiased,Tweeked it a bit and it sounds much better..One of the reasons I asked you the question about biasing I havent been able to find anything much on line that tells about it.I would like to be able to set it correctly.
This is the way I have been doing it.I put my analog Volt meter across the speaker + and - leads of the channel In question then slowly turn the bias setting till the meter is as close to 0 volts as possible.
By the way I havent repaired an amp in about 10 years,I have been working in another busness that got really slow .I still had people asking me to fix there amps
all the time So I set my little repair station back up.I fumbled around the first few days didnt fix a one.Since U started helping me I have repaired 6 punch 45s and one Punch75.
I am about to tackle some larger AMPs If you will help me on it I am going to attempt the massive JL Audios 1000/1 Im am a little afraid of shocking myself.
When I hook it up the low volt light comes on.
Thanks for the info ,Is this setting very criticle? I see that it can cause you to burn your amp up if too high and if to low it dosent sound good.
if I was gonna hotrod a oldschool punch 45 like you tell how to do in your website Is this setting more imporntant to get perfect.Or is it like horseshoes close will do? If I was running the amp at a ohm load that is very low trying to get all the current I can out of .
The setting isn't critical. Setting it as shown in that demo is close enough. There aren't many amps that have enough range for the bias that you can make them sound bad.

The modified amp is less critical and you should probably underbias it. The modified amp isn't for sound quality. It's to squeeze as much power from the amp as possible.
I am gonna take 2 Of these little Punch 45s and do a big time up grade. I am thinking about modifying the Punch 45 that has the fuses . I do not have the original heat sinks
So I will have the luxury of using much larger heat sink and fans . I have a sort of crazy question .
I was measuring the DC voltage across 1000uf caps that are used in the Power Supply. I wanted to see how much the voltage was dropping when I put the amp under a load.With a +-2 ohm load on each channel I played music, it lost down to about +18-18 volts with each Bass note played so it lost over 4 volts total.
Then I checked the voltage across the caps while I pushed a 45hz wave through
the amp with my signal generator. Only a few seconds of this and the voltage had
dropped way below the first measurement it was around +12 and -12 volts.
Is it a bad idea to put two 100000uF 25volt capacitors across this and mount the big caps in the new big case?
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