Paragon - Defective PCB ?

[SCTTWTR]

Hi All-

I finally got around to building my Paragon that I bought about a year ago. It is the version with the separate double switch daughter board / battery holder cutout.

Anyway was getting some weird results with my test rig but went ahead and added jacks and power supply jack and temporaily boxed it and then I was getting absolutely nothing (no signal through either engaged or bypassed both switches).

Started troubleshooting ... verified I had DC power (I built with the gain switch mod that uncouples the charge pump and it seems fine ... getting either (ish volts or 17+ volts).

Setup my signal probe and didn't get too far ... was getting nothing at the input jack ... cut the jack off and tested it with ohmeter and it fine ... poked around and found the + and - pads were shorted (0 ohms between them). Visually solder looked good and no stray wire strands but resoldered anyway with same result.

The + pad looks to connect to a trace that runs along top of board over to the pads that go to the switches. Lightly scrated between the pads on the underside and it looks like the "-" pad connects to a ground plane tha may be shorting the "+" pad on the underside of board (see photo ... best i could get). There are some copper traces running between the 2 pads.
Anyone hear any reports of defective boards ?
Not sure best approach since the board is already fully populated and I spent a fair amount on the diodes to get the right ones.

Thinking I can either scratch some more between the two pads on the underside and see if the short goes away but was hoping one of you experts could verify that the copper traces in the photo are to ground and they go to "-" pad in case I destroy them.

Other option I'm thinking is to cut input trace on top of board and just wire input directly to input switch pad at the front edge of board ... which I think is the first one on the left viewing from top ? (The diagram in the build documents is the PCB with integral stomp switch pads).

Any thoughs from the experts ? As always any comments greatly appreciated since I am a neophyte compared to most of you

 

[Laundryroom David]

Please post pics of both sides of board and all connections.

Board defects are exceedingly rare. Experience has taught me that my own mistakes happen with far more regularity. No criticism implied or intended - just my observation.

 

[SCTTWTR]

No problem ... I 've made my share of mistakes and that's why I've gotten pretty good at troubleshooting these especially simple overdrive pedals.
Anyway here is the other side of the input connection (closeup) and back of board and front of board. I did the tone mod from this forum which are the 2 small MLCC caps on the underside (I put them underneath rather than straddling the resistor on top). Also as mentioned before I didi the switch on the charge pump diodes mod from this forum which is the switch in the photo. They seem fine from my multimeter checks with it powered up. (The input jack is off right now and just the 2 dangling wires where the measured short is).
Thanks for the help !

 

[swelchy]

are the backs of the pots insulated?

 

[Laundryroom David]

no sound in bypass or engaged makes me wonder about those pots as well, but also wonder about your i/o wiring and the footswitches. Do you have continuity in your footswitches? Are both input and output jacks wired properly?

edit: hard to tell exactly, but appears you’ve soldered the output jack backwards in above pic. Looks like you have ground soldered to tip.

 

[SCTTWTR]

Thanks for input but I had already checked all those things.
The covered pots have electrical tape on back and they are not touching anything - verified
The output jack I just switched the wiring color because when I originally wired it to the board I thought the order was same as input (left to right) but according to build document it is opposite ... verified correct according to my multimeter readings too
Footswitches seem fine according to my multimeter readings although it gets a bit complicated with two wired together depending on which switch combination is engaged but kind of hard to mess up if the daughter board and main board pads are correct (I've checked all of the pads and there are no solder bridges and likewise with the switch lugs).

The Input "+" and "-" pads are definitely shorted somewhere so the input is going right to ground. I will do some more tinkering and report back.

 

[szukalski]

Get out the audio probe and schematic. Time to start tracing your way forward and see where it stops.

 

[SCTTWTR]

Yes that is where I started (with audio probe) after I verified the power supply ways good. It literally stops at the input pad on the main PCB. I have a decent probe setup with a tone generator and as soon as I plug input into jack the tone stops because it is going to ground.

Surgically removed the bottom of the input pad grommet ring on the underside of the board this morning with an exacto knife tip so convinced myself that short isn't there.

Thinking of either doing same thing on top of board or cutting the daughter board free in case there is a short in one of the switches or elsewhere. Switch continuity looks good simply checking with multimeter in both positions.

Does anyone know the order of the pads on the main board to daughter board offhand ? (build document isn't labeled). I know far left is input and far right is output and I can see the LED traces. Middle looks like ground. There ar 9 pads. So guesing there ar (2) "SW" and (2) "+" ...I guess I can stop being lazy and measuretrace with my multimeter.

Probably should have just hardwired the 2 switches. Not really a fan of these utility switch boards especially with multiple switches ... IMO they don't save any/much time and they pretty much make the switch useless if something gets messed up ... sorry for the rant ...

Thanks for the help ... you folks in this community are great.

 

[KR Sound]

What do you get when you put your probe on Lug 2 and 8 of the first footswitch? That would be the switch’s in and out. Or can you work backwards from the output when in bypass.

 

[swelchy]

Just to put in my $.02 Electrical tape on the back of pots is lipstick on a piggie… Those little pointy bits on solder joint will poke through the tape and ground out the circuit…Most likely when you box it and pull all the nuts tight and try to test it in the box..
Have you taken out of the enclosure.. bend the pots up a bit and test like that?

 

[zgrav]

tell us more about issues you might have seen in your test rig.

 

[SCTTWTR]

Thanks for the input everyone ... after giving it a rest for a bit I got an idea from szukalsi's post and worked backwards on the input trace ... when I desoldered and removed the input lead between the main board and daughter board (1st one on left) the short went away. Checking the switches again (now I knew exactly what I was looking for) there is a short somewhere (inside ?) one of the switches between the input lug and the center ground lug. So I guess I will cut the daughter board loose and hand wire up a couple of switches.
Thanks again for all the help everyone ... stay tuned I will post final results hopefully when it is working

 

[PunchySunshine]

Thanks for the input everyone ... after giving it a rest for a bit I got an idea from szukalsi's post and worked backwards on the input trace ... when I desoldered and removed the input lead between the main board and daughter board (1st one on left) the short went away. Checking the switches again (now I knew exactly what I was looking for) there is a short somewhere (inside ?) one of the switches between the input lug and the center ground lug. So I guess I will cut the daughter board loose and hand wire up a couple of switches.
Thanks again for all the help everyone ... stay tuned I will post final results hopefully when it is working

Thread 'Paragon footswitch brute trace lifting'
https://forum.pedalpcb.com/threads/paragon-footswitch-brute-trace-lifting.16480/

 

[drew.spriggs]

Thanks for the input everyone ... after giving it a rest for a bit I got an idea from szukalsi's post and worked backwards on the input trace ... when I desoldered and removed the input lead between the main board and daughter board (1st one on left) the short went away. Checking the switches again (now I knew exactly what I was looking for) there is a short somewhere (inside ?) one of the switches between the input lug and the center ground lug. So I guess I will cut the daughter board loose and hand wire up a couple of switches.
Thanks again for all the help everyone ... stay tuned I will post final results hopefully when it is working

Check you don't have a little whisker of solder between the switch lugs - I had HOURS troubleshooting a board that would bypass without power, but would only work when it wasn't bypassed with power.

I had a whisker of solder between the unused LED leg and output leg. No power, board worked fine. Plugged it in, and it sent 9v DC straight into my amp (didn't kill anything, just stopped it working)

 

[Drayve85]

Just saying here, before you get “surgical” check everything else out first!lol those lil copper traces are pare of the ground. The pcb is two thin layers of copper with a layer of phenolic, or fiberglass material in between. Then, the traces are cut out on either side of the traces, so the ‘ground’ is surrounding practically every trace! You should start cleaning you populated boards with alcohol and a toothbrush too! BEFORE adding the pots!!! Alcohol ruins pot tracks, IME!