Generic 1216 driver board


2011-06-08 1:33 am
Hi guys!

just came back after a while... - thanks Perry on this hi-res picture!

I'm repairing this driver board because the output transistors heat-up while rail to rail voltages drops to +-22Volts from +-74Volts. - blue run light lits...

If I removed this board the amp looks fine and railt to rail are +-74V.

Testing and measuring components on this driver board seems fine.

Could somebody tell me what's the problem of this board? I replaced the LM293 but still no luck. How about the two IC's at the input side? Voltages on this board were available.

thank you for having opportunity to talk to you guys...
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2011-06-08 1:33 am
What make/model amp?

It's Sundown. Its generic amplifier.

How much current was it drawing from the 12v power supply when the voltage dropped to ±22v?

Thanks! I suspected my power supply, I fixed it.Now, it goes to protect mode after switching ON. When I bypassed the protect mode by shorting the Pin 1 of TL494 into GND. I got a DC voltage at the speaker output (Approx 2Volts), and my speaker pop out very loud.

I dont know where I can buy this driver board...


2011-06-08 1:33 am
Q7, 11, 19 and 22 commonly fail on those driver boards. Check and/or replace those if you can't find any other problems.

Hi Perry/Guys!

I replace these transistors, Q7,11,19 and 22 but no luck at all.
After I bypassed the protect mode, I measured free flow -74V at the output speaker terminal. I guess IRF640N output transistors are turned ON. While gate terminals are pure DC -65V.
If i'm right, I suspected the waveform generator inside the driver is not functioning.
Can you please help me to understand the job of the two identical IC in the driver board?I dont know their part number.
And which of the part of this board is the signal generator?

Thanks Perry!


2011-06-08 1:33 am
There is no waveform generator. Those are only found on 'clocked' class D circuits. Most class D amps are (unfortunately) self oscillating and harder to troubleshoot when there is a problem.

You need to confirm that all of the voltages on the driver board pins are correct. Post the DC voltage on all of the pins if you need help.

here are the measurements: thanks!
FRom left to right
1. +74
2. +61.8
3. +62.6
4. -73

15. 4.4

16. -73
17. -73
18. -61
19. -73
21. +63
22. +73.7