A couple of questions for you guys

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Jack Dotson, Feb 1, 2012.

  1. Jack Dotson

    Jack Dotson Supporting Member

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    I recently picked up a Marshall 4001 Studio 15, built in 85 and original except for the tubes.

    It has some damage to the knob and some were loose. Also, the volume pot is intermittent. I pulled the knobs off and was able to spread the gap in the shaft's enough to get the knobs back on snugly. However, the volume pot is still intermittent and cuts out until I jiggle it to where it will work. One other is a little scratchy, but after working the other a bit they seem to be fine.

    I pulled the chassis and it looks like the pots are attached to the PCB. They are also gold in color and appear to be Marshall branded. So, is it possible for me to obtain replacements and install? Are there other options, like spraying the pots with some kind of cleaner and if so, how is this done?

    Second issue is with the speaker. It's in good shape, almost looks new, but the dust cover in the center of the speaker has come lose and was laying in the cabinet. The amp is really dusty and dirty and appears to have set for several years. Does it hurt not having it on? And if I can just re-glue it what type of glue should I use.

    I'm not crazy about the Vintage 30 speaker, but these are becoming collectible amps and to keep it original I'd like to get this speaker at least to where I can install if needed. BTW, any recommendations for a good sounding speaker for this amp. Something that would take the top end and add some nice (not flabby) bass?

    Thanks so much.
     
  2. donnyjaguar

    donnyjaguar Member

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    I'm old enough to remember these amps. They sound wretched. I'm surprised they are collectible now.

    I'm pretty sure the pot's are of very light duty design. If the fingers were bent its entirely possible the collective pot' is in need of replacement. Antique Electronics Supply has this stuff.

    I'll let someone else address the missing dust cover and which glue to use. I wouldn't operate the amplifier without it as its likely to draw dirt between the magnet-coil gap and this will shorten the life of the speaker. I'm surprised it came off. Thinking perhaps the amplfiier was in a damp area for a long time.
     
  3. Stu Blue

    Stu Blue Member

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    Clapton did a whole album (I forget which) with a Studio 15... it's a good amp not wretched, just unusual for Marshall. DrZ used 6V6 for the REmedy, his take on Marshall tone BTW.
     
  4. Ronsonic

    Ronsonic Member

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    If the shaft is wobbly in the pot you may be able to recrimp the body of the pot back together. You'll see that it's made mostly of stamped sheet metal and folded together. Take needle nose and carefully tighten it up.

    To clean the pots find an opening in the pot body while the amp is open and give a short spray of DeOxit D5, exercise the pot and repeat if necessary. Info somewhere on my blog.

    For loose knurled knobs, take a q-tip, dip it in acetone, shove it into the hole in the knob and then push the knob into place. The acetone will melt the plastic just enough for it to now have a grip.
     
  5. Jack Dotson

    Jack Dotson Supporting Member

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    Thanks so much for the info. It worked. They're all snug now and the wobble on the volume cap is fixed too. Still have a little noise and cut out so I to get the DeOxit and hope it will help. which I think it will.

    I'm still looking for some info on how to properly re-glue the center dust cover back into place. Have thought about just trying some super glue, but don't want to chance it until I hear from someone who knows.
     
  6. 900z1

    900z1 Member

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    MG chemicals makes a Speaker Service Cement, about 2 oz for $12.00, more than enough to do a dozen speaker dust covers. Active carries it, so does CE.
     
  7. Ronsonic

    Ronsonic Member

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    Most glues will work. I've got a bunch of "official" speaker glue so, of course, I use that. But in the past something like Duco or even rubber cement has done the job. Super glues tend to be brittle and may give up under vibration.
     
  8. Jack Dotson

    Jack Dotson Supporting Member

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    Thanks for the responses. BTW, found an thread with a guy who got a response from Celestian and they said to use white glue, I used a lttle elmers and so far so good. :0)
     
  9. MoPho

    MoPho International Man of Leisure Silver Supporting Member

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    Sooooo...how does she sound?
     

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