Diagnosis of Marshall 8100 Valvestate head problems

Discussion in 'General Electronics Chat' started by HawkDogger, Mar 16, 2015.

  1. HawkDogger

    Thread Starter New Member

    Mar 16, 2015
    1
    1
    Hi Bertus, great response to the very amp I'm working on/trying to understand. I understand your voltage divider calculations but when I use a voltmeter to take readings at R117,118 and 116 I get very low readings. .007 vdc. I thought that maybe the transistor wasn't turned on so I put a 1khz signal through amp and also played my guitar through but very little change. The amps works great so perhaps it's my measuring technique. I measured from one side of the resistors to ground and also across but nothing like the 1.92 volts from your calculation. What am I missing? Thanks.
    e
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Last edited: Mar 16, 2015
  3. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    In normal operation, the voltage will be low.
    The transistor will only be activated when an overcurrent situation occurs.

    Bertus
     
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