Justify cleaning effects loop jacks.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by jbird, Nov 17, 2005.


  1. jbird

    jbird Member

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    I have volume issues with my '99 Mesa Dual Rectifier! Namely, non linear volume drops and increases! I don't employ my effects loop, and have replaced all tubes! I've seen people recommend cleaning the effects loop jacks! How would this work? Thanx!
     
  2. Fuchsaudio

    Fuchsaudio Member

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    Back in the day, I "fixed" more Peaveys by simply working the jacks a few times with a plug and spraying them out it's silly. Not sure if that Mesa has the same arrangement, but it's a likely source. Maybe a jumper cable between the jacks to test the possibilitys.
     
  3. VintageJon

    VintageJon Member

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    As mentioned above- Plug a cable fron Send To Return, (or whatever they are labeled).

    If problem does not occur then it's the N.C. connection on the
    Return jack..

    -Jon
     
  4. trdlasvegas

    trdlasvegas Member

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    On a Mesa Recto, if you have the Effects Loop switched out, those jacks don't even come into play. Your wasting your time cleaning them. That's not your problem.

    -Tony
     
  5. Enzo

    Enzo Member

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    It only takes a second to patch a cord from send to return to find out if it is involved.

    On some amps the loop is always in the circuit. On others, the loop can be bypassed with a footswitch.

    The way it works is this. When you are Not using the loop jacks, ther are internal contacts that carry the signal past them on through the amp. When these contacts get dirty or oxidized, then they can't do their job and you lose the signal.

    Very common problem, and it has nothing to do with brand of amp. I have fixed it on plenty of PV amps, but also had to do it on many Crate amps, and for that matter on brands A to Z.

    If you encounter an amp that changes channels on its own or maybe the reverb is intermittant, check the contacts on the footswitch jack for similar condition.
     
  6. trdlasvegas

    trdlasvegas Member

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    Enzo,
    Your totally correct BUT Mesa's are different. Their Effects Loop can be bypassed from a back panel switch. The switch is actually switching the loop out of the circuit via opto's. With the "Loop Bypassed" there is no signal on these jacks.
    -Tony
     
  7. jbird

    jbird Member

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    Thats what I was thinking! Anyways, the problem persists with or without the loop engaged!
     
  8. trdlasvegas

    trdlasvegas Member

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    jbird,
    I'd take a look at the pots, especially the treble pot. It is very typical for pots to break from pushing on the front of the knobs. In fact Mesa has now installed a nylon washer on each pot shafts to take the shock of the knobs getting hit from the front. What happens is the metal cover over the back of the pot loosens up and they their is less pressure on the wiper to make contact with the carbon track.

    If you take a look under the chassis it is pretty obvious what I'm talking about. In most cases you can just hold the metal can in postion and use a small screwdriver to bend the tabs tight. The upper row of pots may require you to take out the lower ones to gain access to them.

    See if this helps.
    -Tony
     
  9. jbird

    jbird Member

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    I've almost ruled out pots, happens on both channels! It seems only the lower volume regions are affected, with the amp opened up, it performs well!
     
  10. Enzo

    Enzo Member

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    That's certainly true, I have fixed plenty of pots with the back pushed out on these things.

    I don't disagree with your assesment, Vegas, I was more concerned with not wanting folks to think up reasons NOT to check something. You know as soon as you say "well, it COULDN'T be so and so..." that is what it will be. For example, in this case wiring to or the switch itself could be involved.

    On the other hand a failing LDR could fool everyone.
     
  11. Fuchsaudio

    Fuchsaudio Member

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    Never looked at the schemo for that amp, but clearly if the loop is out of circuit when not used, look elsewhere. Good call Tony.
     
  12. rockon1

    rockon1 Member

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    +1
     

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