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Old 23rd January 2012, 12:45 PM   #11
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I will replace those with the correct part and see what happens.
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Old 24th January 2012, 12:23 AM   #12
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That did it. What amazes me is the fact some of the solder joints were factory. So those diodes were replaced with resistors intentionally when manufactured. Maybe that is why the company went out of business. Diablo Audio Technologies, model Hellfire 2500.1 I heard these production model amps would burn up and my guess this is why.

It's to bad it is a nice amp.
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Old 19th April 2012, 03:09 AM   #13
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I'm back working on this, the output fails when driven hard. Only thing I notice is the noisy gate signal on the upper fets. Is this a product of the output filter?
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Old 19th April 2012, 07:27 AM   #14
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Does it look noisy in differential mode?
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Old 19th April 2012, 12:12 PM   #15
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Yes, scope set to add, channel 2 inverted. Here is a pic.

Click the image to open in full size.
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Old 19th April 2012, 12:30 PM   #16
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That's definitely not right. Where does the signal become noisy?

input of opto
output of opto
base of driver transistors
emitter of driver transistors
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Old 19th April 2012, 01:02 PM   #17
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I see it on the +12V supply and the output of the opto.
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Old 19th April 2012, 01:21 PM   #18
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When you captured the last scope image, did you have one probe on the source leg and one on the gate leg?

By +12v do you mean the B+ 12v feeding the amp?
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Old 19th April 2012, 01:49 PM   #19
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If you reference the sinuslive a1500 schematic you sent me, the last measurement was from the drain to gate. The +12v I mentioned is the n_mos12 supply from a secondary winding of the transformer.
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Old 19th April 2012, 04:38 PM   #20
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If you look at the voltage across pins 5 and 8 of the opto-coupler in differential mode, is the DC noisy?

If so, check the capacitor connected across that supply.
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