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Electronics => Repair => Topic started by: d3vCr0w on August 14, 2020, 04:41:29 pm

Title: Guitar pedal with possible input jack ground issue
Post by: d3vCr0w on August 14, 2020, 04:41:29 pm
Hello people, hope you're all doing great. I'm in trouble with this guitar pedal, when I have the instrument plugged in and the pedal is not engaged, the bypass signal goes through and I can hear it, but when I engage it, all I can hear is a 'hum' noise. I took it apart and noticed that there's something wrong with the input jack, I somehow wiggle it and depending on whether it makes a ground contact with the case or not, the pedal works and I can hear the effect (how it's supposed to be), here's a short video explaining it https://www.youtube.com/watch?v=T5Hl-1Lbiro (https://www.youtube.com/watch?v=T5Hl-1Lbiro) and some pictures https://imgur.com/a/EG1OnTf (https://imgur.com/a/EG1OnTf).

Can any of you help me figure out what's wrong with it? Thanks beforehand.
Title: Re: Guitar pedal with possible input jack ground issue
Post by: Buriedcode on August 14, 2020, 05:59:26 pm
Well it sounds like you've already found the problem - the input jack.

Most pedals I've worked on have a stereo input jack - so that when you plug a mono jack into the input it shorts the ring (connected to the battery negative) to the sleeve (which is ground) which turns on the pedal.  The footswitch just switches between the effect and bypass.

I suppose it could be a bad contact with the case as you stated, in which case a simple continuity test between the grey wire on the input jack and the inside of the case.  It couldn't hurt to do the same on the output jack, because that doesn't have a sleeve/ground wire, because it is also in electrical contact with the case.

Either way, with these things, it is often a mechanical failure - the switch, the connectors, or the knobs, things that move. The sockets generally take a bit of a beating, with regular use, and years of rough "stomps" that can hit the jack plug.  I'd just replace both the sockets, they look to be fairly standard - just remember, you'll need one stereo, and one mono, although you could just use a stereo on the output, as you're only connecting one wire to the tip.
Title: Re: Guitar pedal with possible input jack ground issue
Post by: d3vCr0w on August 14, 2020, 06:42:10 pm
Thanks for your reply Buriedcode!, I just checked with the multimeter and there is effectively continuity between the gray wire of the input jack with the case, and between the lifted tab of the output jack with the case.
Title: Re: Guitar pedal with possible input jack ground issue
Post by: Pete66 on August 14, 2020, 07:38:48 pm
Does the LED light up when you turn the switch on?
Are you running it on a battery or adapter?
Title: Re: Guitar pedal with possible input jack ground issue
Post by: d3vCr0w on August 14, 2020, 08:01:16 pm
Yes, the LED turns on when I engage the pedal, and I tried both with a 9V battery and two different power supply adapters.