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Old 11th October 2012, 01:37 PM   #11
diyAudio Member
Join Date: May 2012
Thanks Perry, once I install the new Power and output transistors, I will do exactly what you've suggested. At this point, I've removed both audio driver boards and the main driver board, yes they were the socket style. I do have two more questions while I'm waiting on the new transistors:

1.) Are the rectifiers something that usually go bad and should I be concerned with replacing these as well? What type of reading should I expect from my multimeter?

2.) Is there anything on the audio driver boards that I should be aware of that might possibly need replacing along with the A1266's on the main driver board?

Again, thank you so much for taking the time to help me out here, your knowledge is priceless!
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Old 12th October 2012, 10:39 AM   #12
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Join Date: Nov 2003
Location: Louisiana
The rectifiers rarely fail. When they do fail, you will generally read 0 ohms between the center leg and one of the outer legs.

The low value resistors that fail on these boards should be marked 1R0. They should read 1 ohm. The 12v Zener diodes also sometimes fail.
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Old 14th October 2012, 04:41 PM   #13
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Join Date: May 2012
Ok, I installed all new output transistors, power transistors, I replaced the A1266's on the driver board, I checked the resistors and diodes that you mentioned, along with many other resistors/diodes on this board(gate resistors), I removed the audio boards from the sockets, and I measured the 3rd leg and center leg of the IRF9640's and IRF640's on both sides of the amp for +/- voltage, this is what I found:

With my multimeter switched to "20" the center reads 0 and the 3rd leg reads 0 as well. When I switch the meter to 200m the center leg reads between 0.05 to 0.09. The 3rd leg reads anywhere from NEGATIVE 0.02 to 0.09. This may be to low of a setting, I believe this is the "mili" setting. The question I have now is, when you said to power up the amp for these readings, I currently have a 12 volt source connected to the B+ socket on the amp, with a 10amp inline fuse to protect the power transistors from blowing again. I of course have the amp grounded to the chassis of my car but I have not connected the remote wire because I was concerned about blowing everything all over again!

Is the remote wire needed to test the center and third legs of the output transistors correctly? If I have to connect the remote wire, how will I protect the components from blowing again, IF there's an issue? Will the 10amp in line fuse and the two 30amp fuses inside the amplifier protect my newly installed parts?

FYI, the amp requires 2 X 40amp fuses, as I'm sure your already aware of, but I thought that if I lowered the amperage on the 2 fuses. Please advise me on what I should do next? I believe something is wrong with the way I'm attempting to take these readings? Thanks again Perry

Last edited by ALLMemphisCarAudio; 14th October 2012 at 04:45 PM. Reason: Not spaced properly
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Old 14th October 2012, 06:40 PM   #14
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Join Date: Nov 2003
Location: Louisiana
The 10 amp fuse won't offer much protection unless the current draw is extreme and it blows the fuse quickly. You need to clamp all transistors for the best protection.

Yes, the remote voltage must be applied.

You need to monitor the current draw when you power it up. It may initially draw significant current but the current draw should drop to about 1 amp after about 2 seconds. If it draws more than 2 amps for more than 3 seconds, there is likely a problem.
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Old 25th October 2012, 04:27 AM   #15
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I powered up the amp without the audio boards installed. At first, it went into protect mode but for the past few days, in my spare time, I replaced a few resistors and capacitors here and there that were bad! Tonight, I powered the amp up again, the amp clicked and the amp went from protect mode to the wonderful green light mode! I remembered that the LED doesn't mean anything so I calmed down and followed your instructions!

I took the DC voltage readings on the output transistors and while doing this, the amp let out a horrible squealing sound! I pushed the driver board closest to the RCA jacks down and although it was inserted all the way, the sound stopped.

The output transistors read different voltages depending on whether or not the squealing noise started up or not! I will tell you that while checking the DC AND AC voltage on the 16 pin TL494CN, whenever I touched pin 5,6, or 7, the squealing started again!

The readings on the output legs, as you asked me to get we're:
Leg 1=-54 DC volts
Leg 2=+54 DC volts
Leg 3=-54 DC volts

Leg 1=+52 DC volts
Leg 2=+52 DC volts
Leg 3=+52 DC volts

These readings were taken with a limited power supply too, the readings may have been higher with a full 12V applied

When I installed one audio board, nothing happen that I could tell!
When I installed the second audio board, the amp started squealing bad and the red and green LED lights were lighting back and forth like it couldn't make up its mind whether or not it was gonna go into protect mode or go green!

Please advise about what I should check next, what typical causes the squeaking near the voltage regulators/CT11-D12S(RELAY?)? Thanks again Perry!

Last edited by ALLMemphisCarAudio; 25th October 2012 at 04:32 AM.
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Old 25th October 2012, 07:37 PM   #16
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Join Date: Nov 2003
Location: Louisiana
With neither of the audio driver boards in the amp, there shouldn't be any DC on the center legs of the output transistors. If you have DC, you either have a solder bridge or a leaky/shorted output transistor.
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