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Zoom GFX-5 guitar pedal - no power

Discussion in 'Troubleshooting and Repair' started by StriderSubzero, Apr 3, 2018.

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  1. StriderSubzero


    Apr 24, 2017
    Hi all,

    I have this guitar pedal that does not power on with either batteries or the AC adapter. All the caps look okay, though if you see in photo 1 that random cap on the back of the board. The cap itself doesn't look damaged that I can tell, though it has that substance under it that I assume must be glue. Is it possible this was a factory repair? It looks really strange to me.

    Anyway, I can't tell what sort of fuses this has because I don't have much experience with boards like this, so I can't even tell where the fuse(s) are on this main board. Could someone point me in the right direction? Thank you!

    [​IMG] [​IMG]
  2. Tha fios agaibh

    Tha fios agaibh

    Aug 11, 2014
    I would plug in your power adaptor and check voltage at the jack terminals, establish which pins are positive and neg with your meter. Keeping the black negative meter lead there (first node), move your pos (red) lead along the traces until you find the point where you loose power. Then, swap and check opposite polarity.

    Check the power button for continuity, Check if that square silver component (Fg1) is a fuse in the power rail path.

    Any chance you have a schematic?
  3. StriderSubzero


    Apr 24, 2017
    Unfortunately I do not have a schematic.

    Can you explain what you mean by "swap and check opposite polarity" and why to do that?
    Last edited: Apr 3, 2018
  4. Tha fios agaibh

    Tha fios agaibh

    Aug 11, 2014
    In other words, if you are getting good voltage reading along positive traces, next try the negative rail traces with respect to positive to see if you are losing it along the neg rail somewhere.
  5. nepow


    Jul 18, 2011
    If you are ok with a soldering iron then gently remove the cap noting which way round its mounted. If that's glue it may be similar to an impact type adhesive in which case it may have caused some corrosion around the base of the cap and possibly rotted the PCB through hole tracks! Strange the cap has been mounted on the reverse side of the board unless some one has attempted a repair took out the original cap but couldn't clear its pcb solder through holes, in which case decided to tack on the reverse side.
  6. StriderSubzero


    Apr 24, 2017
    Okay, I honestly didn't understand how to check the continuity on the board besides verifying that the power switch itself was working, but thank you for that tip.

    Somehow I managed to get this working by replacing the cap (which initially did nothing) and plugging it in and fidgeting with it over the course of like 2 hours with a multimeter, trying to figure out what to do.

    I honestly have no idea what I did because the power jack solder points and switch solder points look fine. Thank you all for your help.
  7. Sparoow


    Dec 15, 2019
    Hola yo también tengo la zoom GFX5 y tiene el mismo problema no enciende ni con pilas ni enchufado sospecho que ....puede ser iodo?
  8. davenn

    davenn Moderator

    Sep 5, 2009

    Hi sparoow

    Please post the english translation
    This is an english speaking forum
  9. Martaine2005


    May 12, 2015
    Hello, I also have the same ‘zoom’ and it has the same problem. It doesn’t power on with batteries or plugged in. I suspect........ can it be (iodo) .. no idea what ‘iodo’ is. Google says iodine.

  10. Alec_t


    Jul 7, 2015
    It's a typo for 'diodo' (= diode).
    Martaine2005 likes this.
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