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6G3 - where to find a couple capacitors?

Discussion in 'Shock Brother's DIY Amps' started by Lavely, Mar 2, 2021.

  1. Lavely

    Lavely TDPRI Member

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    My 6G3 build sheet calls for these capacitors:

    .003 uf, 1000V - used on circuit board between V1 & ground
    .01 uf, 1000V - used on tone pot

    I have been looking for Ceramic caps that fit these values, and I can't find them! Where can I buy these, or given the circuit below, are there substitute values that would work?
     

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  2. NTC

    NTC Tele-Holic

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    The 0.003 is really 0.0033uf or 3300 pf. 1000v rating seems a bit much, though this looks like it connects across the plate load. Look up 3300 pf at Mouser. They have mica and film caps that can work. The 0.01 uf should be very common. You should consider a film cap there as well.
     
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  3. dan40

    dan40 Friend of Leo's

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    As NTC mentioned, searching for .0033uf will result in a few more options. Any cap in the 500v or 630v rating will suffice in these positions and may be easier to find. If you are not dead set on ceramic, any polyester or polypropylene film cap will be fine in these positions.
     
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  4. Lavely

    Lavely TDPRI Member

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    Good to go - thanks for the input!
     
  5. NTC

    NTC Tele-Holic

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    If you DO use ceramic for the 0.0033 uf, 1000v is probably the right value. Capacitance in ceramic caps drops as the dc voltage goes up. The can have about 1/2 rated capacitance when operated at their rated voltage.
     
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  6. Nickfl

    Nickfl Friend of Leo's

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    This is a good point, although it should be kept in mind that if you are copying a vintage circuit and using ceramic capacitors because that is what the original used, that poor stability is probably part of the "mojo" and you may not want to go with a part with a higher voltage rating.
     
  7. NTC

    NTC Tele-Holic

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    Would they have used a ceramic cap in a 6G3?
     
  8. Sam VanLaningham

    Sam VanLaningham Tele-Meister

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    Im surprised by this. Im no expert on the circuit but have built two, swapped components a zillion time as well. The .003 should only be hit with less than 200v and the tone pot probably similar, or less!

    I do not think (but also do not know) that the original had these voltage ratings and i dont see other layouts calling for this.

    i and many others just use regular poly caps rated in the 400-600v range in these spots...
     
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  9. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Are you building from the Mojo layout? But without their kit to supply the components?

    Mojo may well just list the specs (like 1000V) their particular parts come with. They may have derived these values somehow, though that's less likely.

    Mojo's a great outfit, but be aware their layouts often have issues, like switching the neutral leg of the household wiring. I like to build to the original Fender layout as a *circuit* foundation but with modern updates to things like power, bias, ground scheme, resistor wattage, etc. Unless Rob has drawn a version of your amp, it's often best to hybridize, to pick and choose from several sources.
     
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  10. NSB_Chris

    NSB_Chris Tele-Meister

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    +1 on this! I have built two Mojo kits Vibro Champ and 5F2A I think and both had errors in the schematics. As I remember, the chassis layout was pretty much correct, but the schematic was had minor errors.
     
  11. David Barnett

    David Barnett Doctor of Teleocity

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    Do they still publish the 5F2A schematic with both caps on the tone control grounded?
     
  12. NSB_Chris

    NSB_Chris Tele-Meister

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    Don't remember. Maybe that is the issue I was thinking of. I do remember that the VibroChamp had something wrong with the vibrato circuit.
     
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