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Old 25th July 2013, 12:04 AM   #1
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Default Dead Kicker ZX650.4

Hi there - I am new to this forum and really hoping I can get some assistance here.

I have a Kicker ZX650.4 that doesn't power on. There is nothing visually wrong with the components on the board and the amp itself was only used for about a week (at moderate volumes) before it failed.

I've taken it apart, and with guidance from Perry's car audio repair tutorial I've learned a great deal about amplifiers and poked around some of the components.

I have a soldering iron, basic tools, and a Fluke 117 multimeter.

I believe either the TL494 or the emitter follower BJTs are defective. I don't think the output voltage from the driver IC is high enough to turn on the FETs. Without further ado:

TL494:

1: 1.072
2: 3.127
3: 0.062
4: 0.001
5: 1.511
6: 3.419
7: 0.001
8: 2.163
9: 0.701
10: 0.701
11: 2.162
12: 12.97
13: 5.009
14: 5.009
15: 5.009
16: 4.047

From looking at the board, it appears that the two emitter follower pairs are being driven from pins 9 and 10. However, surely the voltage there should read higher? I'm not sure what the function of pins 8 and 11 is in this particular amplifier, but I believe these should be higher too.

All of the voltages on the gates of the power FETs are equal: 0.568. None are shorted. If this was an issue with one of the emitter follower BJTs, I'd see different gate voltages on from one bank of FETs to another, right?

Please let me know what else I should check. I am not averse to desoldering components, but would prefer to start with simpler tests. Thanks in advance
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Old 26th July 2013, 12:07 AM   #2
RiLoWa is offline RiLoWa  United States
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The low voltage on pins 8 & 11 is not allowing the 494 to turn on and function causing the low output you measure on pins 9 & 10.

You need to find out why there isn't ~12V there by working back from those pins to find the defective component.
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Old 26th July 2013, 02:34 AM   #3
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Indeed! The problem was a blown PNP BJT in position Q6. Had slight visible burn mark that became visible upon closer inspection. It fused open.

Thanks for the help!
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