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Fender Twin & Deluxe Reverb Input Jacks....horrible part!

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  • Fender Twin & Deluxe Reverb Input Jacks....horrible part!

    In the past, as well as now, while going thru the inventory of Fender Twin Reverbs, I've had so much trouble with the stupid plastic open-top T/SN input jacks...particularly on the Normal Channel (for reasons unknown). Why this part became a 'standard' in their better combo amps is beyond me. What so often happens in time with these jacks is you loose ground continuity. Ground is made by a rectangular 'hoop' routed up and around the 3/8"-32 threaded bushing part pressed into the plastic body, and pressed into the grooved channels around this ground bushing. Oxidation eventually sets in, the press-fit loosens and you suddenly have loud barking from the channel if your cord's phone plug is pulled to one side or another. And, the Normal contact doesn't always make good contact, so you have hum that comes and goes when you disconnect while the volume control is up. These are the parts I"m talking about:

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    I've even installed brand new jacks like these, fresh out of Fender's spare parts packages, and you STILL have the same problems over in the Normal Channel. And, of course, a couple de-solderings of the jacks on that input PCB assembly and you've now gotta repair the PCB, as the tiny annular ring solder terminals designed on the board by the novice PCB layout person who don't know squat about serviceable solder pads have lifted off the PCB. Those input boards in general need to be re-designed, just from a service stand point! Fat chance of that happening.

    I finally went in and retro-fitted some proper Switchcraft L12A open-frame T/SN phone jacks, and wired them in, scrapping these plastic wonders. There is enough space below to do it.

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    Those open frame jacks that we've been using for decades just can't be beat. Granted, not PCB mounted, so you have more fumble factor, particularly if you used the thin ITL washer between the chassis and the jack as I did, but all the jack problems are gone. No more scary noises when the cord is tugged on, nor do the cords pull out if you move out to far away from the amp (debatable attribute).
    Logic is an organized way of going wrong with confidence

  • #2
    Fumble Factor?

    What, a couple of jacks?

    I can deal with that if one comes in.

    A true 'Fumble Factor' would be anything made by Mesa Boogie.

    Comment


    • #3
      Agreed, better to fumble with a couple awkward retrofits than explain why newly replaced stock jacks still have the same problem .
      There's always the "jack-on-a-stick" solution, either make your own or get one something like this:
      STEWMAC.COM - Jack Installation Tool
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


      Comment


      • #4
        Nice clever tool, but completely unrelated to what we're talking about here
        Juan Manuel Fahey

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        • #5
          I took it that the "fumble factor" was a reference to it being a little more difficult to do future work on the jacks or the pot board due to them no longer being board mounted.
          I thought that a tool like that would make the task easier. It looks like there may be room for the chassis mount jacks to be installed after the board is back in place using such a tool.
          Originally posted by Enzo
          I have a sign in my shop that says, "Never think up reasons not to check something."


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          • #6
            [QUOTE=nevetslab;369821
            Those open frame jacks that we've been using for decades just can't be beat. Granted, not PCB mounted,[/QUOTE]

            Exactly why I like them.
            It's weird, because it WAS working fine.....

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            • #7
              Originally posted by g-one View Post
              I thought that a tool like that would make the task easier. It looks like there may be room for the chassis mount jacks to be installed after the board is back in place using such a tool.
              Heck I make my own "magic arm" with a foot or so of 12 ga solid - works great for fishing jacks into place on a hollowbody, and on rare occasion, tighten up an amp jack that's lost its nut. But I don't see how such a tool would really help here. If you're committed to making the amp work near-to-forever as possible, plastic board mount input jacks OUT, Switchcraft 12A or L12A IN. On some amps, I've cut away corners of the preamp circus board to fit 'em - no plan to retreat. Forward into the past, use what's been proven to work.
              This isn't the future I signed up for.

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              • #8
                I'll just say uncle then.
                Originally posted by Enzo
                I have a sign in my shop that says, "Never think up reasons not to check something."


                Comment


                • #9
                  Cha-Ching!
                  Easy money repairs.
                  I probably do about 50/50 ss vs tube gear, and the PC board stuff is usually easier.
                  And Mesa Boogies I love getting in ( not really) but those usually yield good money due to them being such a pia.

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                  • #10
                    Someone please help me, I have a fender twin reverb amp reissue. I'm getting audio out of both of my virbato channels but not the normal two channels, I tried switching to switchcraft, I tried swapping tubes, someone please help me troubleshoot.
                    Last edited by JosephhhGee; 05-23-2015, 06:54 PM.

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                    • #11
                      By "no audio through the normal channels", do you mean no sound at all, as in silence, or is there some noise? And if there is some noise, can you make it change by manipulating the input plug? One quick and easy thing to try is to swap the first two 12AX7 preamp tubes. The first one is the normal channel, the second one is the vibrato channel. Does anything change?
                      It's weird, because it WAS working fine.....

                      Comment


                      • #12
                        Originally posted by Randall View Post
                        By "no audio through the normal channels", do you mean no sound at all, as in silence, or is there some noise? And if there is some noise, can you make it change by manipulating the input plug? One quick and easy thing to try is to swap the first two 12AX7 preamp tubes. The first one is the normal channel, the second one is the vibrato channel. Does anything change?
                        I get speaker noise, when I turn the volume up it gets louder, but when I plug into channel 1 and 2 nothing happens, I tried switching the tubes already and that wasn't it.

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                        • #13
                          How good are you at troubleshooting a tube amp?

                          What test equipment do you have available?

                          Do you understand what is involved in safely working on a tube amp?

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                          • #14
                            Originally posted by Jazz P Bass View Post
                            How good are you at troubleshooting a tube amp?

                            What test equipment do you have available?

                            Do you understand what is involved in safely working on a tube amp?
                            I operate a studio so I have access to whatever I need, and I work on amps all the time I don't think there's a safety issue. We try to fix our own gear hear instead of sending it out obviously, but we can't get these 2 channels to work.

                            Comment


                            • #15
                              Good to know. Good to Know.

                              First off, prove that you have a connection from the Normal input jack to V1/ pin 2.
                              Should be 68K or something. #2 input will be higher still.
                              Go right into the jack with a guitar cord. Measure the tip to V1/ pin 2.
                              You can also prove out that the jack has ground. Ring to chassis.

                              If so, prove that you have the necessary voltages for V1 & V4 to work.
                              Pin 1 & 6 : plate voltage
                              Pin 3 & 8 : cathode voltage
                              Pin 4 & 9 : Vac heaters.

                              65_twin_reverb_ SM.pdf

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