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Another amp blowing fuses... but why?

Discussion in 'Amp Tech Center' started by MrCoolGuy, Jul 10, 2020.

  1. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    Oh... that schematic does say "47n"
    If you're gonna handwrite a schematic... maybe print... I don't know, legibly...
     
  2. tubegeek

    tubegeek Friend of Leo's

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    You also have to READ with reality in mind.

    That schematic does NOT call out a .047 uF/600V cap as its primary reservoir feeding the output transformer. Regardless of what it looks like it says, which is debatable.

    nF is a typical value for coupling caps.

    uF is the only suffix you will ever see in guitar amp power supply filters. You can take that to the bank.

    Whoever installed that cap had absolutely no business opening an amp chassis - it's a good thing they weren't electrocuted.
     
  3. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    I'm not saying that cap is good or bad...
    But it is where it shows in schematic, is it not? But it definitely came from Mesa like that. It's on every SOB I can find online. Here's 5...
     

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    Last edited: Jul 25, 2020
  4. tubegeek

    tubegeek Friend of Leo's

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    OK then are the two stacked caps with two stacked resistors 120pF or 120uF each? Must be uF in which case I misunderstood what was going on. 47nF/600V makes sense if there are 120uF+120uF stacked on the other side of the switch. (Equivalent of 60uF.)

    I take back what I said above, I was misreading the (illegible) schematic this whole time. My bad.
     
  5. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    No, it's cool. The other two are 220uf each.
     
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  6. tubegeek

    tubegeek Friend of Leo's

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    In series, the equivalent is 110uF. The two resistors balance the voltage between the two caps so neither one sees a DC voltage beyond their rating.

    Together, THOSE are the main reservoir cap.
     
  7. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    Gotcha. Thanks.
     
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