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Fender Princeton 112 Plus Pop and Master Volume Mod

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  • Fender Princeton 112 Plus Pop and Master Volume Mod

    Does anyone have the Pop and master Volume schematics and instructions for the mod that fixes the pop and add a master volume to the old Princeton 112 plus amps? Lots links to an old post on this.. but that post is long gone... Anyone have a copy of a decent write up on how to do this?

    THanks

  • #2
    The popping is discussed here: https://music-electronics-forum.com/...tronics/49657-

    I don't see as there was any easy solution unless adding capacitors to the power switch reducse the noise sufficiently.

    As to the master volume... Why? The amp isn't designed to make more distortion beyond the volume controls that are in it. In other words, the volume controls that are there now ARE (sort of) master volumes for their respective channels.

    And... It's customary to provide a schematic when asking for circuit evaluations. You didn't, you asked if there were known modifications. But we may need this anyway

    Click image for larger version  Name:	pp1.png Views:	0 Size:	601.7 KB ID:	955223
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    • #3
      If you just gotta have a MV, the simplest thing to do is slap a volume pedal in the FX loop.
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        Originally posted by Enzo View Post
        If you just gotta have a MV, the simplest thing to do is slap a volume pedal in the FX loop.
        Sure. Though I can't see that it would do anything the existing volume controls don't do? And it looks like the reverb circuit and effects loops are parallel. So it would only attenuate the dry signal.
        "Take two placebos, works twice as well." Enzo

        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

        "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

        Comment


        • #5
          Originally posted by Chuck H View Post

          As to the master volume... Why? The amp isn't designed to make more distortion beyond the volume controls that are in it. In other words, the volume controls that are there now ARE (sort of) master volumes for their respective channels.
          I almost got the impression that Steve A came up with that as a way of dealing with the 'pop' (turn down prior to turn off). https://music-electronics-forum.com/...198#post458198

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          • #6
            Originally posted by Chuck H View Post

            And... It's customary to provide a schematic when asking for circuit evaluations. You didn't, you asked if there were known modifications. But we may need this anyway

            Click image for larger version Name:	pp1.png Views:	0 Size:	601.7 KB ID:	955223
            Thanks,

            I'm actually looking for the schematic that documents the Mod that Steve Aloha posted about 7 years ago. The Master Volume control is a crutch for the old Princeton Plus 112 Amps as Fender failed to install a logarithmic potentiometer and used linear volume pot... As a result these amp are super sensitive from 0-1 and then are just way too loud and over driven after that. There are a couple of older YouTube vids that try to document the mod (with links to long lost posts here) I was hoping that either the original poster is still here and could send me the instructions and parts list needed or... That someone else had done the mod..and had a copy of the process.

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            • #7
              Well, sorry to say Steve passed away quite some time ago. You can visit blueguitar.net and look around.
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                This, perhaps?

                https://music-electronics-forum.com/...ome-mods-i-did
                "Take two placebos, works twice as well." Enzo

                "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

                Comment


                • #9
                  Ok, anayzing the Princeton 65r it is indeed basically the same amp.
                  Regarding the pop they added :
                  1) a 100nf/250V X rated cap before the transformer
                  2) a 100nf/250v x rated cap after the transformer
                  3) 100nf decoupling caps on all opamps rails

                  For the volume they didn't touch the pots but lower the gains of following stages

                  Also the power amp is a total redesign (and they added a zobel network on the out)
                  it seems a better design overall

                  If I have time I'll post the changes on the schem

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                  • #10
                    also there's a 1meg resistor on the power amp in

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