Request for help finding GND on GCB 95 circuit

[jfd986]

Hi everyone.


Would someone be able to tell me where the "GND" or "Ground" is on this pedal, so I can do all of Aron's recommended debugging and then follow up with a completed post for all to review?

Here are pictures, and below is what I have so far for the troubleshooting post, which won't go up officially until my multimeter diligence is complete.

I don't know how to read a schematic, I usually find the circuit board picture with the lines going to the components etc but none of the internet pics of the Wah pedal seem to look like the one I have here.

Thanks in advance.











(Future post below, not complete yet)
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I have a Dunlop Cry-baby wah (not a DIY) where the sound is cutting out when the pedal is turned "on". Or the sound is cutting out when the pedal is turned "off" and the pedal isn't making an effect when turned "on", I figured the former is more likely than the latter, I am a novice at this though.

I think? This is a link to a schematic for the pedal.

https://www.freestompboxes.org/viewtopic.php?f=7&t=24983#p242455

I did not build this one, I am trying to help someone repair it for the experience of pedal repair. I have not made any modifications to the pedal, but it does come with a fasel inductor.

It is a center negative pedal in terms of polarity.. I can't really figure out from the schematic whether it's a positive ground or negative ground, I just know that this "ground" aspect of the pedal has not been modified from stock.

[GibsonGM]

Welcome to the forum!  One way to find out is connect 1 end of your DMM to that center pin on the power jack (when unplugged) and probe around using continuity setting - the beep is ground.   Zero ohms when set to resistance is the same thing.  Don't use your meter for this with power plugged in.

Another is to use the first metal tab on the jacks, closes to the hole you plug your cord into.  That is usually gnd, confirm against that gnd center pin.  I'd plug a cord into the input when testing (disconnect power unless measuring voltages!) since the input jack switches ground (turning on power to the circuit...it connects the gnds of the board to the gnd of power supply. You might get crap readings otherwise).

On a negative gnd circuit, you can find gnd by putting one probe on the metal sleeve of a plugged-in cord and locating a point with continuity on the board (the sleeve of the plug is grounded). 

[antonis]

Below are 3 obvious GND points..
(GCB95 is a negative ground pedal..)

[Rob Strand]

This thread has the schematic for the SMD version,
https://www.diystompboxes.com/smfforum/index.php?topic=98281.0