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Help with Musicmaster Bass Amp

Discussion in 'Amp Owners Clubs' started by whatdisay, Jan 22, 2017.

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  1. whatdisay

    whatdisay TDPRI Member

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    Houston
    I'm at my wits' end trying to get the tone stack on this amp done right. I bought a '77 Fender Musicmaster Bass Amp in September. After reading on this forum and others about the Harvard tone stack mod, I took it to my tech in November.

    In early December I got it back, plugged it in and there was a big leap/jump in tone and volume when rolling up the tone knob (I think around 4). Clearly the tech had not fully tested it out with a guitar after making the mod. Took it back in early December.

    Just got it back today. While there is no longer any big jump when rolling up the tone knob, now when the tone knob is all the way down the amp is not dark--certainly not as dark as the amp should be with the tone knob at 0.

    Just wondering if someone might be willing to walk me through checking out what the tech did and possibly fixing this myself. If so, please send a PM, or if you're interested in sharing on here, great. I could take some pics of the chassis if that would help. For all I know the tech didn't even make the proper Harvard mod.
     
  2. czech-one-2

    czech-one-2 Friend of Leo's

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    Hi, a little late to your question but I tried the Hassrl Harvard vol,tone wiring and didn't like it. I finally got around to wiring the pots like a typical Fender Deluxe and its perfect.
    Check the diagram and just ignore the second vol pot. Use a 1meg vol pot if you have one.
    Also, if you add the one meg resistor to the input jacks you can remove the 470k resistor in the MMB.
    I also don't like jumpering that .0047 cap on the input as it adds break up and drives the 12ax7 harder. Might be what you want though.
    I've got mine sounding exactly like I wanted it and this tone/vol arrangement was part of it. Just solder that .0047 cap on the tone control to the back of the pot.
    [​IMG]

    [​IMG]
     
    Last edited: Jun 18, 2017
  3. czech-one-2

    czech-one-2 Friend of Leo's

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    Aha, this thread is in the wrong forum. Maybe the mods can move it?
     
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