# Son of Ben: Shorting when pots are tightened



## ch ra (Aug 26, 2020)

I feel very stupid right now posting this, but I think it's time to get an outside perspective. I built the Son of Ben and it sounds spectacular. The problem is, when I boxed it and tightened up the nuts on the pots (not ridiculously tight, just a bit more than hand tightening) the sound and power cut out. I thought it might be the dual gang pot, which does not have a plastic dust cover. I had put tape between it and the PCB, but I went through several iterations or more tape and plastic thinking that something was shorting under the dual gang pot. That didn't work.

Today I went back and tried again and now I've shorted out the LED. The rest of the circuit is ok though--it plays fine when the nuts are loose and reliably shorts when they are all tight. This is really puzzling because the short is happening between DC+ and DC-. I am not seeing the Vcc points shorting to ground, and it looks like D100 is intact. This makes no sense to me because the DC jack looks fine and I don't even see how I could get a short between the + and - ends with the standard pedalpcb wiring setup. I can post a picture, but it will be hard to see much of the back side of the PCB (where the short is most likely taking place) because the pots pretty much cover everything. 

Does anyone have any thoughts here? Thank you!


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## moonlightpedalbuilds (Aug 26, 2020)

Try checking if the pots are soldered properly on the board on both sides.


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## ch ra (Aug 26, 2020)

It looks like this is the case at least for the top of the PCB. But I need to unbox to check the bottom side. Shot of the PCB top is at the following link:
https://ucdavis.box.com/s/8at4bqz402yjfm6bfpj7lhuxj86cyx3u


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## ch ra (Aug 27, 2020)

Here are more pictures (the forum won't let me upload them because the files are too large:
https://drive.google.com/file/d/1Tp44jUplO2qsgUoYJUa93cqXRG5MkKtS/view?usp=sharing
https://drive.google.com/file/d/1Lvkr7nv6ynaNoRBQ1pIIPEDfxqqKPAcC/view?usp=sharing
https://drive.google.com/file/d/1QEm_F88iMWHnTSuBstEvWsFxlZa9ruBs/view?usp=sharing

I resoldered the pots and will try again, but I'd really appreciate it if someone could take a look and see if you can spot anything. Thanks!


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## Robert (Aug 27, 2020)

I don't see anything that stands out but I will say that every time a build involving a dual pot has an issue like this it has been the dual pot causing the issue.

On the other hand, is that a metal LED bezel I see in your pic?     The +9V pad is directly above it, that could certainly cause a short to ground. (and would explain your issues with the LED)


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## ch ra (Aug 27, 2020)

@PedalPCB Thanks for taking a look! You might see in the photo that I had put electrical tape under the dual gang pot, but that didn't prevent the problem. Also, looking at the schematic, I am not sure how shorting any of the pads under the dual gang would cause continuity between the + 9v and ground inputs. 

It doesn't look like the LED bezel can make contact with the +9V pad, but maybe I can remove it and see if it makes a difference. I am not sure what else to try at this point!


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## ch ra (Aug 27, 2020)

Well I took out the LED Bezel, boxed it again, and it looks like it works fine even with the pots very tight. I am not sure the bezel was the problem, because I also replaced the electrical tape under the dg pot with paper and I re-soldered the pots. But I am thinking that the bezel is the most likely culprit, given the 9V pad. I just don't see how they would contact each other though. Does this mean I should give up on the bezel? Could it be that one of the leads from the LED was making contact with the ground or the 9V pad?


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## moonlightpedalbuilds (Aug 27, 2020)

Metal bezel? Happened to me before. The LED leads can touch them and mess up your pedal. Slap some tape on the legs.


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## Robert (Aug 27, 2020)

ch ra said:


> Could it be that one of the leads from the LED was making contact with the ground or the 9V pad?



Yep.  The LED anode is directly connected to the +9V line (before the 1N5817 protection diode) so if the leads managed to touch the side of the bezel that would do it.


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## ch ra (Aug 27, 2020)




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## ch ra (Aug 27, 2020)

OK, @PedalPCB I think your explanation has to be right. I'll install a new LED, put heat shrink on the legs and have the legs poke out of a strip of electrical tape that will serve to cover the bottom of the bezel. That should be enough, right?


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## Nostradoomus (Aug 27, 2020)

Just heat shrinking both legs should be fine unless the board is making contact with the bezel.


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## ch ra (Aug 29, 2020)

It's working and sounds great, thanks everyone for your help! Gotta say, it is impressive how this pedal sounds considering the simplicity of the circuit!


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