Frying an Ernie Ball by using 'wrong'/'damaged'/ageing Y-cable

Discussion in 'Effects, Pedals, Strings & Things' started by nitefly7, Mar 10, 2008.

  1. nitefly7

    nitefly7 Member

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    Hi guys 'n gals,

    I just noticed that my Musicom midi-switcher gets reset when I'm using a particular Y-cable to use my Ernie Ball VP Jr as an expression pedal..
    By moving to the 0-position, the Musicom locks up and reboots..

    To make things worse, my VP Jr. smells like burnt electronics..!
    Using another cable makes the problem disappear, so I'm guessing it's the cable... (it's a Tasker insert-/Y-cable..)
    Using another cable helps the 'reset'/lock-up problem go away, but I'm wondering if it's not just a matter of time until this cable starts acting up..

    any thoughts?
     
  2. this1smyne

    this1smyne Member

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    i just use the output on my vp when i'm using it with line 6 pedals... i'm not sure if the switcher uses the TRS cables or not....
     
  3. nitefly7

    nitefly7 Member

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    what kind of cable are you using? a single TRS-TRS ?

    the switcher is supposed to use the TRS cable..
     
  4. Scrutinizer

    Scrutinizer Member

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    To understand what happened, it is necessary to understand how the expression pedal works. The expression pedal connects via a TRS connector. Shield is ground, obviously. The tip and ring carry reference (Vref) and control voltage (Vcontrol). There is no industry standard that specifies which signal (Vref or Vcontrol) corresponds to tip or ring.

    In the expression pedal, Vref connects to one side of the pot, and ground to the other. Vcontrol is the pot's wiper.

    What can happen if we connect Vref to the wiper, then set the expression pedal to heel-down position? Vref is shorted to ground! If the Musicom device connects it's internal supply rail directly (i.e. no current limiting resistor in series) to the expression pedal Vref output, it would explain the reset you observed. This connection shorted the internal power supply to ground!

    There is a good chance that the burning smell is symptom of damaged pot in the VP JR. As you approach heel-down position in the VPJR, the resistance between wiper and ground approached zero. And as resistance decreases, current increases (assuming voltage is steady).

    FWIW, I don't have a Musicom product. But I do have some EB VPJR pedals, successfully used as expression pedals with a number of effects units & midi footcontrollers.
     
  5. nitefly7

    nitefly7 Member

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    wow thanks! I figured it had to be something like that (voltage/current), but wasn't really sure..

    But is there any reason why the effect only takes place with a shorter insert cable?
    using another (3ft instead of 1ft) insert cable doesn't produce any reset at all...!
    Or is it only a matter of time before this cable will cr*p out on me too ?

    I'm using the pedals as expression with much luck, but as soon as I move to heel-down, with that one cable; reset-city..!

     
  6. Scrutinizer

    Scrutinizer Member

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    So ... it resets in heel down, but otherwise works correctly? That is really strange.

    Without knowing more about the Musicom unit, I am very hesistant to make suggestions. What does the owner manual say about expression pedal connections? Have you checked your insert cables with a DMM? Perhaps the 'tip' and 'ring' labels are not on the correct wires. What happens if you reverse the connection at the VPJR?
     
  7. nitefly7

    nitefly7 Member

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    it works perfectly, until I 'heel down' using that one cable (maybe cross-talk?)

    If I use either the VPJR or the 6188 (is that the big one?), with my other y-cable; it's a 100% working thing, without any glitches or resets..

    The manual states:
    "The EFX Mk II contains a XPDLXPDLXPDLXPDL port for expression pedal input. This can be
    used to alter parameters(via MIDI) in effects device that offer this capability.
    These setting is Global(the same for all banks/presets). Any passive volume
    or expression pedal can be used. Recommended pedals are Boss FV500L/H,
    FV300L/H, FV200 and FV100.
    The cable required is a stereo (TRS) to two mono 1/4" phone plugs. Connect
    the tip(stereo plug) to the pedal input, ring to the pedal output and sleeve to
    ground on all 3 plugs. See chart below.
    Stereo 1/4" plug MONO 1/4" plugs
    EFX Mk-II Pedal in = out
    Tip --- Tip (pedal in)
    Ring --- Tip (pedal out)
    Sleeve --- Sleeve(both in and out) "

    If I reverse the jacks on the VP jr, it's a no-go..
    But it only happens with the one Y-cable..

    would just buying a 'expression pedal' with a single TRS-single TRS work, or would I suffer the same problems, you think?

    Would the 25k pot matter ? I know the FV-300L (recommended ones) have a different one, but would that matter a lot?

     
  8. nitefly7

    nitefly7 Member

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    do you think the cable will matter this much?
     
  9. Scrutinizer

    Scrutinizer Member

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    Sorry, I don't have any more answers for you. The behavior you describe (works if heel-down avoided; heel-down resets unit) does not make any sense if the expression pedal wiring is correct.
     
  10. nitefly7

    nitefly7 Member

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    then my best bet would be a faulty cable; trying a different cable with 2 different EB's leads to 0% failure...

     

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