SOLVED Duocast enclosure grounding/short issue

[caiofilipini]

Hey all,

I recently finished building my Duocast, and the circuit. works fine outside and even inside the enclosure, but there's definitely something wrong with the input and output jacks, because it only works if the jacks are not attached to the enclosure. As soon as I get them through their respective holes, it stops working. If I move them around inside the holes, I get signal sometimes (I assume when they're not touching the enclosure). So it seems the wiring itself is correct because I get signal when the jacks aren't attached. The enclosure doesn't have any paint on the inside, but I filed around the jack holes anyway to make sure. I also used the exact same jacks (Lumberg) in my Paragon build without any issues.

Here are some pics:







Looks like I have some short/grounding issue, but I couldn't identify it myself. I know searched through older threads and saw most folks who had similar issues were using metal DC jacks, which isn't my case here.

Any thoughts?

Thank you!

 

[Robert]

It's not the jacks... Something else is touching the enclosure (or the back of a pot, etc) somewhere.

The enclosure is floating until the jacks make good contact so there is no problem. Once the jacks have a good connection it brings the enclosure to ground potential and the short becomes apparent.

Short version: The issue with the jacks is a side effect, not the cause.

Did you use metal LED bezels by any chance? If so make sure neither of them are touching the back of the board.

 

[Nostradoomus]

Give your board a good cleaning with a toothbrush and isopropyl alcohol, top and bottom, and see what happens.

 

[caiofilipini]

Did you use metal LED bezels by any chance? If so make sure neither of them are touching the back of the board.

I didn't use metal LED bezesl, they're plastic. But I think this was it:

Give your board a good cleaning with a toothbrush and isopropyl alcohol, top and bottom, and see what happens.

I had cleaned the back of the board before soldering pots and switches, so now I cleaned all of it again and that seems to have done it!

I'll post the results in the Build Reports forum as soon as I find a Germanium transistor that sounds good. I tried an OC71 and an AC128, and both sounded kind of boomy to my ears. I then tried a 2N404 that sounded better, but I got a couple more transistors I want to test before closing it up.

Thanks both of you!

 

[caiofilipini]

Here's the finished build:

Duocast

After an issue with enclosure shorts, here's my latest build, the Duocast: I used a BC549C in Q1 and an NOS GT2308 in Q2. I actually tried a few different transistors in Q2, including an OC71, an AC128, and a 2N404. The 2N404 and the GT2308 sounded better in my opinion, and I ended up...

forum.pedalpcb.com

Thanks again!