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Old 05-21-2019, 08:50 AM   #51
R_J
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Join Date: Jun 2012
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Default Re: Onkyo SKW-591 subwoofer is dead

If you look at the schematic you will see where the ground is. That large black ground line that connects to q501 pin2. There seems to be only one voltage that does not use that ground, that is Q501 pin 12 vcc, It uses the minus of C503 or the minus of C902. If you follow the VCC (Q501,Pin12) it goes through R528, to VB Q901 (78M12) This 12 volt regulator has it's ground connected to -B so to measure THIS voltage you would just measure across C907.
If you used the normal ground to check this voltage it would not show correctly, it would likely show around -30 volts.

If you don't have VAA +5volts that will throw off the bias of the whole amp circuit so you will likely show a high voltage on the speaker terminals.
Again just look at the schematic, +40 comes to R433 and connects to Q433 emitter, this transistor acts like a switch, R435 should be low on the end opposite the transistor. If the transistor is turned on you should have ~10 volts on the input of Q435 and +5 on the output.

Last edited by R_J; 05-21-2019 at 09:26 AM..
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