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Old 25th June 2010, 03:20 AM   #11
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You could try it but it's unlikely to help with this. They are generally removed when you have only half of the waveform being produced.

Is there any DC on the output?
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Old 25th June 2010, 03:27 AM   #12
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Alright, no significant DC ~15mV.
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Old 25th June 2010, 03:44 AM   #13
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What is the voltage across R166 (on the schematic diagram). It's part of the constant current source for the differential amplifier. The resistor may be R106 on the main board. It's probably the only 820 ohm resistor near the driver board.
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Old 25th June 2010, 12:23 PM   #14
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I read 0 across R106.(1K)
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Old 25th June 2010, 12:35 PM   #15
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Is that the same resistor (one end connected to the emitter of Q112 and the other end connected to the negative regulated 12v)?

If so and you read 0.000v across it, there is no current flowing through constant current source and the differential pair so there's no way for the amp to produce audio. Try removing Q114 from the driver board to see if the current across that resistor increases.
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Old 25th June 2010, 01:43 PM   #16
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R105 ties to the emitter and R106 to the base, they both tie to -12V. I can send you the 40DSM schematic if needed.

I lifted Q114(Q101 on the 40) and have 56mV across R106.
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Old 25th June 2010, 02:03 PM   #17
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Send it to me.
babin_perry@yahoo.com

That's still not enough. I'd expect ~8-10v across the resistor that's connected between the emitter of the CCS transistor and -12v.

What is the voltage across R112 and R113 on the driver board?

Also measure the DC voltage from the supply side of the resistors to ground.
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Old 25th June 2010, 03:02 PM   #18
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It slowly ramps upto 65mV sometimes on both and I have 46Vdc from supply to gnd.
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Old 25th June 2010, 05:35 PM   #19
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Does the voltage change on the base of Q112 when you turn the bias pot?
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Old 25th June 2010, 06:08 PM   #20
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Yes, starts at -11.45V and drops as you turn it cw. I have it all the way ccw now when I start.
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