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If you set the trace to the reference line and the scope is set to DC coupling and the trace is at -50v, how can it be above the reference line?
I found with the irs2092 class d IC if the mosfets failed they often took out the 2092 too.
Any gate drivers should be tested too.
Any gate drivers should be tested too.
Sorry! I thought all you wanted to see was the wave form. I just moved it up on the scope so you could see it. Didn't even think to set the trace to the reference line. My mistake. I'll set the trace to the reference line and take another pic. Do you want it with signal in or without. If signal in, how much? Thanks!
On the oscilloscope page of the site (page 73), there is a 'best initial settings' section. Read through that section. USe the vertical amp and timebase settings you did previously.
Without signal, it's likely to be just a straight line. Take it as you did above.
Confirm that your scope's trace deflects to about -80v(or whatever it reads on a multimeter) and remains there when you touch the negative rail. If it does not, confirm that the negative speaker terminal is at 0v and ground your scope to the negative speaker terminal.
Post a photo showing the deflection of the negative rail (for reference).
Without signal, it's likely to be just a straight line. Take it as you did above.
Confirm that your scope's trace deflects to about -80v(or whatever it reads on a multimeter) and remains there when you touch the negative rail. If it does not, confirm that the negative speaker terminal is at 0v and ground your scope to the negative speaker terminal.
Post a photo showing the deflection of the negative rail (for reference).
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"On the oscilloscope page of the site (page 73), there is a 'best initial settings' section. Read through that section. USe the vertical amp and timebase settings you did previously" - What site? I clicked the link for new site. It said forbidden.
"Confirm that your scope's trace deflects to about -80v(or whatever it reads on a multimeter) and remains there when you touch the negative rail. If it does not, confirm that the negative speaker terminal is at 0v and ground your scope to the negative speaker terminal."-The scope has been connected to the negative speaker for all tests. Rail voltage is + and - 87VDC. Tested both with the volt meter on the scope and with a Fluke 8024B. Adj. trace balance. Made sure I had equal deflection positive and negative. Both are deflecting to about +80 on the positive rail and -80 on the negative rail.
"Post a photo showing the deflection of the negative rail (for reference)." - Sorry about the glare in the photos.
"Confirm that your scope's trace deflects to about -80v(or whatever it reads on a multimeter) and remains there when you touch the negative rail. If it does not, confirm that the negative speaker terminal is at 0v and ground your scope to the negative speaker terminal."-The scope has been connected to the negative speaker for all tests. Rail voltage is + and - 87VDC. Tested both with the volt meter on the scope and with a Fluke 8024B. Adj. trace balance. Made sure I had equal deflection positive and negative. Both are deflecting to about +80 on the positive rail and -80 on the negative rail.
"Post a photo showing the deflection of the negative rail (for reference)." - Sorry about the glare in the photos.
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R190 and R192 check good. Tested Q126 and Q127 out of circuit. Tested good. Replaced anyway with new MPSA56 transistors. No change in the sign wave. Voltages are the same.
There are several parallel transistor locations where either can be used. It's the transistor with its collector driving Q124-127 and has a 1k resistor between its base and secondary ground. Q118 is probably right.
Of course. I should have just assumed that. Checked good. Replaced anyway with a new MPSW92. Signal and voltage still the same.
I think you stated that the board wasn't burned internally. Did you use a bright enough light and look between the terminals of Q124/125 as well as between the resistor labeled C191 and Q124?
Rechecked. I don't see any dark areas around any of the transistors. Used a bright LED light and Mag glasses.
Unless someone else has suggestions, you may be left to check all connections and all components (out of the circuit, checking for leakage and open junctions) in the low-side drive circuit.
I have another amp here. I'm going through the driver board on it. I'll try it in this amp and let you know if it is the driver board. Thanks
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