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Do These Adj DC Offset - Pioneer SX-9000

Alaska Bill

Alaska Bill

Member
Oh generous helpful learned ones, are the two circled variable resistors the correct ones for adjusting the DC offset on the Pioneer SX-9000. Thumbnail is the schematic of the main amp unit (W15-052).

Many thanks...Bill
 

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Alaska Bill said:
Oh generous helpful learned ones, are the two circled variable resistors the correct ones for adjusting the DC offset on the Pioneer SX-9000. Thumbnail is the schematic of the main amp unit (W15-052).

Many thanks...Bill
Click to expand...

This one's humble opinion is that the circled variable resistors DO :thmbsp: adjust a DC voltage, called C+ voltage on the schematic (it should be 1/2 of the B1 or B2 voltages), but this DC voltage CANNOT be measured at the speaker terminals due to the presence of the 2200uf 50v capacitors, which is what one normally thinks of when the words DC offset and hi-fi amplifiers are mentioned together.

I'm picking nits here.... :stupid:
 
Hummm

Thanks for the reply, Mark.

So I thought I was going to be measuring DC offset (in the mV) range. But it is like you said, C+ (39V) is about half of the B1 voltage (83V).

So is it possible to measure DC offset in this receiver or is it not possible due to the caps (2200/50V) being in the circuit? Just trying to understand at this point.

Bill...
 
Alaska Bill said:
Thanks for the reply, Mark.

So I thought I was going to be measuring DC offset (in the mV) range. But it is like you said, C+ (39V) is about half of the B1 voltage (83V).

So is it possible to measure DC offset in this receiver or is it not possible due to the caps (2200/50V) being in the circuit? Just trying to understand at this point.

Bill...
Click to expand...

Trying to say it ANOTHER way, there IS NO DC OFFSET. IT IS CAPACITOR COUPLED. The dc voltage is measured across a 1k resistor or less at the speaker terminals and if there is ANY appreciable DC the cap is BAD. The reason for the 1k resistor (or speaker load) is that there is a LITTLE leakage, and the super high (10 megohms) resistance of the voltmeter would make it look worse than it is.
 
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