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  • bad hum Blues Junior

    Hum all the time, I have installed the upgrade output transformer, and the amp already had the presence control, twin tone stack mod.

    Trouble is that I'm getting constant bad hum at idle. speaker, cables, tubes have been ruled out. the EQ can change the sound of it, but still sounds like a ground problem. any ideas ?

  • #2
    Sounds like my problem I've posted on within yesterday and today. This occurs with no input device (guitar) plugged in? Sounds like you have done Bills mods. I did them about a year ago and the results where outstanding but my amp developed a similar hum recently. The hum changes as I change the position of the V1 ribbon cable (last one on the right when looking at the back of the amp). In some positions, feed back occurs. Is something oscillating???

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    • #3
      It could be getting worse. - almost sounds like when a guitar cable is plugged in and you hold the end of it in your hand instead of plugging a guitar in it, but not quite as loud! I've spent more time and effort on this amp than I should have. The hum is very annoying. of course can't hear it when cranked, but ...

      anyone have a link to the proper wire dress inside. Maybe I have the wrong set of wires braided or something..

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      • #4
        the presence control seems to have the most effect on the total hum and is almost gone when it's wide open, but it probably is just accenting whatever comes through it.

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        • #5
          Bluespower, Did you do any of the Bill M mods to your blues jr? I've been checking out his new site, its pretty cool. Maybe I'll dig into mine after all. Some advise on where to start to get rid of a hum with nothing plugged in to it would be great though.

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          • #6
            yes, it has the twin stack mod, the presence control and the upgraded transformer. it sounds pretty good in a larger 1-12 cabinet and a better speaker...... until I blew an EL84, which shorted and burned R33 resistor. got it fixed and it was OK for about an hour. Iit's been humming ever since. It may have to go back to the shop if I don't get some leads.

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            • #7
              Does the quality of the hum change if you move the ribbon cable coming from V1 (the 12ax7 tube on the far right)? I don't know if you're comfortable around live voltages..if not don't mess with it. If yes, use a chop stick or something wooden and just move the ribbon cable. I'm thinking that mine has a bad solder connection somewhere on the lower chassis.

              If your amp only worked 1/2 hour after the repair, I would bring it back to the tech.

              I'm thinking I may just go to another amp eventually...something with no printed circuit boards. Although I do love the tone I've been getting out of this tghing until recently.

              Good luck, Pete

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              • #8
                I just found this on Bills site (http://billmaudio.com): Bad Filter Caps in New BJrs

                I’ve got yet another Blues Junior on the bench with bad filter caps. In this one, all three of the 22μF filter caps had leaked. The owner had sent it to me with a note requesting the usual mods, plus a rather plaintive “… and maybe you can find out why it hums while you’re in there.”

                Virtually all of these failures are on rev. C (2003 or newer) cream boards, and they’re almost always the 22uF filter caps, not the larger 47uF. They’re not stressed very hard in the Blues Junior, so I think that Illinois Capacitor (the IC brand) cranked out a bad batch of caps. The leakage looks like tan foam or glue, right around the + lead of the cap. Sometimes it drips onto the circuit board.

                The symptoms may include hum, buzz, or high-frequency oscillation. Or sometimes a dirty, raspy edge to the notes that just doesn’t go away. If your Blues Junior exhibits any of these symptoms, definitely check out the filter caps.

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                • #9
                  Had one more thought. The tube socket holes may need to be tightened up a bit. Any advise from you very knowledgeable members?

                  I'll give it a rest til I get a chance to really have a look at it, hopefully tomorrow.

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                  • #10
                    Fender has had a few problems with their amps, filter caps and tube sockets being the most common.

                    Yes bad filter caps can cause hum or oscillations in the amp.

                    The bad tube sockets are black in color and the contacts will not hold their shape, causing the tubes to fit so loosely that they will literally fall out of the sockets. Replacement is the only real fix for these sockets. The current ones are light brown or greyish brown in color.

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                    • #11
                      I have the light brown tube sockets and all of them are tight. I see no leakage from the caps at all. Its a 2003 model.

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                      • #12
                        A bad cap will not always show signs of leakage.

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                        • #13
                          it's at the techs (again) and I'm quickly losing confidence in the BJ's durability, or maybe the tech ?1?!?. I'll report back when it returns and let you know what he found.

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                          • #14
                            maybe try different outlets, I have a blues junior when I first got it was quiet, but for no reason it started buzzing after a couple of days since then, I can't play it in my basement cause it makes that buzzing sound.

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                            • #15
                              already did. Several. I even went to a GF outlet just to be sure. It's a hum, as if you grabbed the end of a guitar cord while it was plugged in to the amp. all the time, with all controls on zero.

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