Foot switch solution gone horribly wrong

Discussion in 'Amp Tech Center' started by Mexitele Blues, Aug 25, 2019.

  1. Mexitele Blues

    Mexitele Blues Tele-Meister

    Age:
    41
    Posts:
    394
    Joined:
    Mar 7, 2018
    Location:
    Westminster, CO
    I wanted a single 2 button foot switch that would fit on my pedal board and could pull double duty between my Peavey & Fender amps. So I bought this FS, which works fine with my Peaveys:

    p-h471_copy.png

    https://www.amplifiedparts.com/products/footswitch-marshall-two-button

    And this adapter to plug into the rear of my silverface Pro Reverb:

    31HpCe1zKrL._AC_SY400_.jpg

    https://www.amazon.com/dp/B000068O5C/?tag=tdpri-20

    Now on the fender there is serious buzz when the reverb is on. The buzz gets louder with the reverb knob until 7 when it develops into a full-on squeal.

    I'd checked the schematics for reissue fenders that use a single TRS plug for the FS against my Pro's. The only difference I see between them is where the FS grounds come together. The newer style has the grounds connect inside the FS, then use the sleeve to connect to chassis, whereas the older rca plugs keep the grounds separate until they reach the chassis.

    65_Deluxe_Reverb_RI_Schematic.gif

    Pro Reverb - 74-75 Master Volume.jpg

    Have I created a ground loop by splitting the FS grounds with the adapter? If so, the reverb driver's cathode is grounded directly to the reverb FS jack, inside the loop. Could this cause the squeal? Maybe I can lift the sleeve connection on one leg of the adapter.
     
    Last edited: Aug 25, 2019
  2. 24 track

    24 track Doctor of Teleocity Silver Supporter

    Posts:
    13,660
    Joined:
    Nov 6, 2014
    Location:
    kamloops bc
    couple of question here first
    1) does the fender reverb buzz or hum with out the pedal?
    2) do you NEED the pedal to operate the fender reverb?
    3)could you open the pedal and take a picture of the wiring ? ( it would be easier to identify any possible issues with your rig)

    here is the inside of the fender pedal for my 65 twin RI ( the jack terminates to a RTS 1/4" [ring /tip/sleve] part of the problem MAY be that the peavey and the Fender use two differnt grounds

    P1012253.JPG
     
  3. Mexitele Blues

    Mexitele Blues Tele-Meister

    Age:
    41
    Posts:
    394
    Joined:
    Mar 7, 2018
    Location:
    Westminster, CO
    24 track,

    -The reverb is dead quiet without a FS, and with the original fender FS.

    -I would strongly like to have the reverb switchable.

    -The schematic of the new FS matches that of the DRRI's above.

    I covered the reverb FS jack with electrical tape to break the ground connection. It worked and everything was quiet! So I dug into the adapter and cut out the sleeve connection in that wire. Tested no continuity and taped it up. Pulled the tape off the jack. Still noise. I'm a little confued about that one.
     
  4. milocj

    milocj Friend of Leo's Ad Free Member

    Posts:
    3,532
    Joined:
    Aug 21, 2005
    Location:
    Michigan
    Is the lead on the footswitch that operates the reverb a shielded cable? Fender reverb runs the signal through the footswitch so that side has to be shielded to keep it quiet.

    The trem side doesn't need the shielded wire so it is a single conductor that grounds through the switch housing and the shielded run.
     
    Mexitele Blues likes this.
  5. Mexitele Blues

    Mexitele Blues Tele-Meister

    Age:
    41
    Posts:
    394
    Joined:
    Mar 7, 2018
    Location:
    Westminster, CO
    Ok that's got to be it. It is unshielded cable.
     
  6. 24 track

    24 track Doctor of Teleocity Silver Supporter

    Posts:
    13,660
    Joined:
    Nov 6, 2014
    Location:
    kamloops bc
    this is the fender RCA type footswithch notice that only one lead is shielded the other is just hot , what you may have to do is look at how this pedal is wired inside and duplicate that for your peavey pedals , theground may be wire so the the reverb switch is shielded but the temolo os just a short to ground , if that is the case it should be a simple fix to get it to work with both amps , is the Peavey solid state or tube ? the reason why I ask is that Solid state amps do not use a chassis ground but Isolate the circuits from chassis ground.

    Screen shot 2019-08-25 at 1.38.12 PM.png
     
    Mexitele Blues likes this.
  7. Mexitele Blues

    Mexitele Blues Tele-Meister

    Age:
    41
    Posts:
    394
    Joined:
    Mar 7, 2018
    Location:
    Westminster, CO
    (Foot) Switching gears, the fender FS with adapters to 1/4" TRS male works on the Peavey. I had just enough adapters to get there.

    20190825_142725.jpg

    I just can't use the fender's form factor. It's shape isnt conducive to pedal board layout, and it is too low and its buttons too close together for big feet.

    I suppose it's time to play Dr. Frankenstein and order one of these.

    41ELP3CoVAL._AC_SY400_.jpg
     
  8. Mexitele Blues

    Mexitele Blues Tele-Meister

    Age:
    41
    Posts:
    394
    Joined:
    Mar 7, 2018
    Location:
    Westminster, CO
    I'll swap the shielded cable into the new housing shown above and order a different adapter to use with the peaveys. Should be good to go after that. I am not sure about ss vs tube peaveys, as I have both, but they are compatible, foot switch-wise.
     
  9. 24 track

    24 track Doctor of Teleocity Silver Supporter

    Posts:
    13,660
    Joined:
    Nov 6, 2014
    Location:
    kamloops bc
    I get you on that,the pedals you ordered should work fine for both amps ( i dont use my fender pedals at all) , I built my own pedals to work with my system , I was asking about the SS v/s tube incase you were looking at an A/B situation for using both amps ( that may cause issues for you)

    heres what I built to make my system work

    pedalboard 20-42-45.jpg P1011758.JPG P1011968.JPG P1011996.JPG
     
    Mexitele Blues likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.