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Adjusting the idle current on the Pioneer A-107.

Does anyone know how to adjust the idle current on a Pioneer A-107, I've downloaded the circuit diagram but it doesn't have this information.



Re: Adjusting the idle current on the Pioneer A-107.

Yes, the service information is totally useless; no procedure at all, not even voltage readings. If that were my amplifier, I would adjust for minimum DC voltage on the outputs, then check the output transistors to make sure they did not overheat.

Re: Adjusting the idle current on the Pioneer A-107.

Thanks Johnnysan,
Someone has suggested checking out the service information for the Pioneeer A-207 which is very similar and much clearer, and includes idle current adjustment.

Re: Adjusting the idle current on the Pioneer A-107.

Hi!
From quiescent current is independent constant output voltage at the output of the amplifier. Only the power consumption - heating and distortion. - Often, the more heat, the lower distortion. Thus turning VR301 and VR302(Idle Adj) - you can change the quiescent current. Himself current can be measured by the voltage drop on the R373 / 375 and R374 / 376, respectively. In your case, I guess the quiescent current should be 50-100mA - resistors - voltage drop 5.5-10mV DC. At the moment, you need to try on the voltage drop across the resistors of the above, to assess the heating radiator (it should not be more than 50-60C after heating of 0.5 hours) and understand for myself -what we want and whether we need it? -If current is different in the right and left channel - to align with each other very slowly rotation VR301 / 302, and the watching voltage drop R373 / 375 and R374 / 376, respectively. -After This for 0.5 hours in a custom control whether the current channel and the heatsink. - If inaccurate quiescent current regulation likely failure of the output stage transistors Q323-326.
All measurements and adjustments are made without a signal and acoustics. Volume knob - at the minimum position.
After all, verify that the DC voltage at the amplifier output - left leg (under the scheme of service manual) of resistors R381 / 382. It must be less than 100 mV. If it is a few volts - I congratulate you burned your amplifier...