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Old 16th September 2012, 09:48 AM   #11
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This amp uses 2sa1015 as drivers, collector is tied to ground.
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Old 16th September 2012, 10:15 AM   #12
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Are you sure that those are the right transistors?

Unless this amp uses a drive circuit that's very different from most amps, that transistor should be a PNP transistor.

Does this amp use an emitter follower pair (NPN and PNP transistors) for the drivers?
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Old 16th September 2012, 10:24 AM   #13
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It is PNP transistor.2SA1015 is printed on the board on all 4 locations for drivers. Two have their bases connected to pin 9 of 494, two of them to pin 10 of 494.

All collectors tied to ground, emitters connect to gates of two IRFZ44N through a 100 ohm resistor.
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Old 16th September 2012, 10:53 AM   #14
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I misread the part number. Does the amp use any NPN drivers or does it have a diode connected across the base and emitter of the PNP driver?

If it uses a diode, what is the DC voltage on pins 11 and 12 of the 494?
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Old 16th September 2012, 11:12 AM   #15
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It uses a diode.
Voltage on pins 11 and 12: 9,8 and 8,9V.
Voltage across B+ and GND: 10,2V
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Old 18th September 2012, 11:10 AM   #16
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Why is your power supply producing only 10.2v DC?

What is the amplitude of the square wave on pins 9 and 10?

How does that compare to the voltage on the gates of the FETs?
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