Valvestate 2000 avt 275

Discussion in 'The Workbench' started by Susan Shocks, Aug 10, 2011.

  1. Susan Shocks

    Susan Shocks New Member

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    Location:
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    Hi Guys
    I've been asked to take a look at a friends 2000 avt 275. There's absolutely no sound AT ALL coming from it, not even through the headphone socket. I changed the 12AX7, and I've jumped the effects loop, but still nothing. Also, there's no LEDs on the front panel switches. He didn't leave the footswith with me, but surely you can manually switch without the footswitch????

    Any help much appreciated

    Ta!
     
  2. SFGTech

    SFGTech New Member

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    I just sent one of these out the door after fixing a problem that seems similar to this ... Is the power switch light on? If it is and you have no lights on the panel (od1/2 and so on) then inside the amp 2 2.2ohm resistors have blown ... These resistors are being used as fuses :wtf: .

    All I did was trace the problem straight to these resistors which took all of 5 minutes to desolder and replace ... they are on the board and schematic r202 and r223 and the replacement is 2x 2.2ohm 1/2watt resistors ... I will expect to see this amp back in my workshop in about a year with the same problem :( .

    The science behind it: the 2 resistors each take about 0.13w of dissipation ... when one shorts (Goes open circuit) the other takes 0.51w of dissipation. Now in conclusion you could replace these with 2 2.2ohm 1watt resistors but without a full test I cannot garrentee the outcome will cure the problem in the long run ... Also what the hell were marshall thinking when trying to use resistors as fuses!?

    If you need any help or if you are in my area (Bournemouth) then feel free to shoot q's at me :)
     

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