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Old 1st October 2012, 08:09 AM   #11
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It's an old Russian scope. If you tell me what settings to use, I can try to use it, but the waveform isn't going to be pretty. Also, my multimeter can measure frequency.
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Old 1st October 2012, 08:40 AM   #12
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For the gate waveform, use 10uS and 5v/div.

You should read the oscilloscope page of the car audio site, pay close attention to information in the section "Best Initial Settings".
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Old 1st October 2012, 11:42 AM   #13
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The waveform below is the mosfet drive signal pulsing. Sorry about the bad quality of the pics. I used 2V/div instead of 5V, because the amplitude wasn't enough and it was too difficult to see anything. Doesn't appear like a proper square wave to me.
Attached Images
File Type: jpg IM000579.JPG (388.7 KB, 22 views)
File Type: jpg IM000581.JPG (393.2 KB, 20 views)
File Type: jpg IM000571.JPG (637.5 KB, 20 views)
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Old 1st October 2012, 11:49 AM   #14
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It appears that the pulse width is changing rapidly. Which of the pins of the driver IC have DC voltage that's not constant?
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Old 1st October 2012, 12:27 PM   #15
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These are the voltage measured from tl494.
1: 0V
2: 3.95V
3: 59mV
4: pulsing between 1.6V and 2.7V
5: 1.07V
6: pulsing between 2.2V and 2.5V
7: 0V
8: 12.4V
9: pulsing between 150mV and 350mV
10: same as pin 9
11: 12.4V
12: 12.4V
13: pulsing between 3.7V and 3.9V
14: same as pin 13
15: 3.88V
16: 0V
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Old 1st October 2012, 12:32 PM   #16
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Lift pin 4 from the socket and connect it to pin 7 of the IC. Does that make the voltages more steady?
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Old 1st October 2012, 12:43 PM   #17
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Lifted the pin 4 from the socket and shorted it to pin 7 of the IC. The protection LED was still pulsing, but now the amp started drawing current and the mosfets got warm.
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Old 1st October 2012, 05:48 PM   #18
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Can you see a cleaner square wave?

Did the voltage on pin 14 return to 5v?
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Old 1st October 2012, 06:21 PM   #19
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No, pin 14 is still at 0V. When the jumper is in place, the gate drive signal is wider. Please see the attached pic.
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Old 1st October 2012, 06:33 PM   #20
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The IC cannot operate with pin 14 at 0v. Re-check the readings. If it's still 0v (or well below 5v), find what's dragging it down.
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