Re: Need Help with this Circuit Please
But are they being Bias ON and OFF (no Gate Voltaeg applied) by the control circuit to mute the signal. Put in new parts does not mean they are working if it is not getting the Voltages. It is like putting in new light bulb but you still have bad light switch.
Those FETs work like as I explained before about the input of the power amp being grounded out (by the FET) to mute the input signal to GND.
You have one FET per channel (Q201, and Q217) for muting, both FETs are being controlled by the same control line as you see in the circuit page 25. Since both channels are making noise then it has to be something in common which will be the control line to both, but if one channel does not make the thump then it is not the control problem but the FET or the components connected to that muting circuit for other channel that is bad.
You need to check the DCV between the Source and Gate to see the Voltage level changes when the unit is powered up and when powered down.
J112 is the N-CH JFET.
Page 2:
Low RDS on at zero gate voltage.
No GATE Voltage means the audio is Grounded out.
Originally posted by tfs2015
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Those FETs work like as I explained before about the input of the power amp being grounded out (by the FET) to mute the input signal to GND.
You have one FET per channel (Q201, and Q217) for muting, both FETs are being controlled by the same control line as you see in the circuit page 25. Since both channels are making noise then it has to be something in common which will be the control line to both, but if one channel does not make the thump then it is not the control problem but the FET or the components connected to that muting circuit for other channel that is bad.
You need to check the DCV between the Source and Gate to see the Voltage level changes when the unit is powered up and when powered down.
J112 is the N-CH JFET.
Page 2:
Low RDS on at zero gate voltage.
No GATE Voltage means the audio is Grounded out.
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