Wired DC jack backward on Clandestine preamp

[mathteam]

Hey everyone, first time post here.

I recently built the Clandestine preamp and it had worked when I tested the board using a screw terminal DC jack for testing (everything else was mounted in the 125b). When I added the DC jack to the box, I accidentally wired it backward. It didn’t work when powering on (of course) but now it also doesn’t work after I switched the connectors between the jack and the board. I’m using an MXR iso brick for the power supply. Did I fry something on the Clandestine board? If so, which components need to be replaced?

Pics:



Thanks in advance!

 

[Mcknib]

Replace or jumper the 1N5817, D100 that's the most likely culprit

 

[blackhatboojum]

What Mcknib said. D100 is a reverse polarity protection diode and is there for this very reason. Did you leave it hooked up and powered in reverse for very long?

 

[Robert]

D100 shouldn't have been damaged by reverse polarity, that's why it's in series. The idea is that it will block reversed polarity without damaging any components. (Unlike a parallel diode to ground which can short and take out PCB traces with it)

If you have a DMM measure the DC voltage on both ends of the diode and see what you get.

 

[Mcknib]

It's a shame the datasheet doesn't tell you how long you can reverse polarity but it can take up to 24V I edited that bit out just thought too much Info

Not 100% but if C100 blows would that not stop power

 

[mathteam]

Thanks a ton! It was only connected for a short time (guessing around 30 sec). Do diodes have any visible proof of failure to look for?

Thinking I may have some issues with DC jack also -- potentially a short or something. The power supply showed similar behavior (indicator light flashing on and off for that port) even after I switched the +/- on the DC connectors.

I’ll dive into it tonight and will report back. Really appreciate the insight in this.

 

[blackhatboojum]

You can't always tell by physically looking at a component whether it's bad or not. As Mr @PedalPCB suggested, check your voltage on both sides of the diode. I would also check the voltage on the dc jack and that port of your power supply. It's possible that the power supply took some damage.

 

[mathteam]

Pretty quickly into investigating, I found a short across the power terminals on the pcb.



Good lesson in clipping leads (and tinning them properly) I guess.

Power supply seems to be fine.

Does it make sense for the pedal to sound best with the bias trim pot fully ccw? I’m using the ear technique for biasing and it seems to go from no sound (fully cw) to noisy (mid way) to clean (fully ccw) with no real peak in sound quality. Maybe worth trying out a few other 2n5457s?

P.S. what’s the etiquette here on secondary questions? New thread or same thread?