MOSFET failure? Help diagnosing problem

Discussion in 'General Electronics Chat' started by Veracohr, Apr 4, 2016.

  1. Veracohr

    Thread Starter Well-Known Member

    Jan 3, 2011
    551
    76
    The attached circuit is the input stage of a guitar distortion pedal I'm trying to fix.

    The problem is that the gate voltage isn't what it should be and the transistor is off. When powered up the DC gate voltage is about 72mV. R2 and R3 measured in-circuit are quite different from what they should be: R2 measures 93.6k/90k and R3 measures 80k/82.4k. There's two numbers for each because they measure differently depending on which way the meter leads are connected. There are no other components in parallel with R2 or R3 which would account for the differing values.

    Could a MOSFET failure account for this? There's no visible damage.

    Screen Shot 2016-04-04 at 6.34.52 PM.png
     
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