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Old 5th December 2010, 06:07 AM   #11
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Can you desolder Q515? If you can lift two legs and leave it in place, it will be easier to reinstall it later.

The transistor is under the preamp board near the large white resistor near the speaker terminals.

It's going to appear that it's leaking if you check it. That's normal.

With that transistor out of the circuit, does it produce audio at a normal level?
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Old 5th December 2010, 04:51 PM   #12
ivkata is offline ivkata  United States
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Yep i took it off and now the amp works great.Man u really know ur amps ,what parts i have to replace
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Old 5th December 2010, 05:00 PM   #13
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I don't have a schematic diagram so I'll have to trace the circuit back on a junk board I have here. I may not get a chance to do this until tomorrow.

What is the resistance between the two legs on the bottom of the transistor? It should be about 30 ohms.
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Old 5th December 2010, 05:41 PM   #14
ivkata is offline ivkata  United States
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my meter shows 28ohm so its accurate to ur reading
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Old 6th December 2010, 12:28 AM   #15
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Since the amp is working, measure the DC voltage directly across the speaker terminals (red on +sp term, black on -sp term). What is the DC offset?
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Old 6th December 2010, 04:57 AM   #16
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Check that transistor to confirm that the gate (at the top of the transistor) is not shorted to the other two legs. On diode check, you should read ~0.6v one direction and open when you reverse the position of the probes.
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Old 6th December 2010, 01:21 PM   #17
ivkata is offline ivkata  United States
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sorry for the delay in repply i had internet conection problems.I mesured the dc offset at the speaker terminals and its steady 0.00v from min to mac gain.when tested the transistor shosw ~0.9 one direction and ~1.2 in the other
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Old 6th December 2010, 07:50 PM   #18
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If at least two of the legs of that transistor were off of the board, it appears to be defective.
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Old 6th December 2010, 10:10 PM   #19
ivkata is offline ivkata  United States
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I took it of the board just to verify the test and the same result came
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Old 6th December 2010, 10:21 PM   #20
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Replace it and post the results.
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