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Son of Ben (no sound when engaged)

robfallon

New member
hi there. I've built up the son of ben twice now. both times i've had the same issue. signal passes thru just fine in bypass. No sound when on. I've read a few threads on here about bad jfets. My first time i got some off of eBay... 2nd time bought from mouser. Same results no mater the transistors. I do get a little bit of scratchy sound when moving the trim pots, but no signal output. I've tried an audio probe, but I get nothing at the input jack as soon as the pedal is on. that tells me something is grounding out the input feed on the board but I can't for anything find what it could be. All the solder joints look good.. no stray wires. I've triple checked polarity on capacitors, diode, etc... Any ideas? (FYI, yes im a noob. please take it easy on me. The B1M solders look a little rough cause i've removed that pot a couple times troubleshooting) I have wrapped the back of the B1M pot with electric tape. shouldn't be the issue. Thanks in advance.IMG_0975 1.jpg
 
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phi1

Well-known member
What do you have in for R1? Looks like brown-black-gold-gold, which is 1ohm instead of 1M... which would explain why it’s grounding your input signal.
 

robfallon

New member
What do you have in for R1? Looks like brown-black-gold-gold, which is 1ohm instead of 1M... which would explain why it’s grounding your input signal.
ok wow... you are correct! i am an idiot. wrong resistors ordered and installed. Don't have any 1M on hand so will have to wait a bit to swap. thank you!
 
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phi1

Well-known member
No problem, your description of the problem was thorough and led me right to it.

Same for R3.

If you have enough extra 470k, you could put 2 in series to approximate 1M, should be close enough for this application...
 

zgrav

Well-known member
resistors, capacitors, and diodes are cheap compared to shipping costs. always order a few more than you need to build up a small inventory.
 

robfallon

New member
No problem, your description of the problem was thorough and led me right to it.

Same for R3.

If you have enough extra 470k, you could put 2 in series to approximate 1M, should be close enough for this application...
Ah ha. just tried that. Got me over the hump past the grounding out issue. Of course found a new one. I should hopefully be able to diagnose with the audio probe. thanks.
 

Grayscale

New member
I'm having the exact same issue with Son of Ben. I rewired the whole thing, LED and bypass work but there's no output. I got the Jfets from Amazon so I'm suspicious of those. I have a DMM on the way to see what's really going on. IMG_2859.jpg
 

phi1

Well-known member
@PedalPCB I think it would be helpful to have a note on the build docs of any J201/2N5457 circuit that folks are best off using SMD jfets with the adapter board you sell, unless they know for sure they have a good source. I myself got tripped up on this the first time I tried to build with J201s.

Grayscale I'm not saying that's definitely your problem. But even if you find another problem and get it working there's a chance those j201s are way out of spec and it won't sound like the original anyway. I'd recommend check the voltage at the drain of each jfet, and using an audio probe to see where you lose the signal.
 

thedwest

Active member
I'm having a relatively similar problem with mine although its most likely user error on my part. I just boxed it up and get no sound when its engaged. However, I unboxed it and it works fine. After some simple troubleshooting, it looks like my input and output jacks are grounding out when tightened into the enclosure. I can't for the life of me figure out why thats happening.
 

thedwest

Active member
Me neither. Maybe a pic or two would help.
This is after I tried adding some tape as a buffer. Long story short, I originally built this with an A500K pot in place of a A1M. It worked out of the enclosure but I didn't like the sound of the A500K. I swapped that with a B1M and was able to tweak it enough that I liked it. I boxed it up and it stopped working. Thought it might have had something to do with the pot, so I swapped back to the A500K. Then as I was putting the audio jacks back in, I saw the LED flicker and I'm assuming burn out, because it stopped coming on even when I had sound and when I replaced it it started to work again. So where everything stands, is that if i leave everything boxed except the jacks, it works. If the metal of either input or output jack touches the enclosure, it goes silent. Everything also still works in bypass, whether the jacks are touching the enclosure or not. I'm assuming that somewhere i created a grounding issue when I swapped out pots but I've looked over everything and cant find an issue.


IMG_3815.jpegIMG_3817-1.jpeg
 

Chuck D. Bones

Well-known member
Don't trust the tape to insulate the pots, trimmed leads can easily poke thru. Use actual dust caps or cardboard. You can install a dust cap on a dual pot, but it needs to be trimmed a bit. The parts in the sockets, are they in tight? Those sockets are made for IC leads which are larder diameter than transistor leads. A thin coating of solder on the leads will fatten them up a bit. Clean the board and inspect the solder joints.
 

zgrav

Well-known member
another thing to check is whether your your jacks might be shorting out to the case when your audio cables are plugged in. do you lose the sound when the jacks are mounted to the box? or only when you close the box?
 

thedwest

Active member
This is after I tried adding some tape as a buffer. Long story short, I originally built this with an A500K pot in place of a A1M. It worked out of the enclosure but I didn't like the sound of the A500K. I swapped that with a B1M and was able to tweak it enough that I liked it. I boxed it up and it stopped working. Thought it might have had something to do with the pot, so I swapped back to the A500K. Then as I was putting the audio jacks back in, I saw the LED flicker and I'm assuming burn out, because it stopped coming on even when I had sound and when I replaced it it started to work again. So where everything stands, is that if i leave everything boxed except the jacks, it works. If the metal of either input or output jack touches the enclosure, it goes silent. Everything also still works in bypass, whether the jacks are touching the enclosure or not. I'm assuming that somewhere i created a grounding issue when I swapped out pots but I've looked over everything and cant find an issue.


View attachment 4037View attachment 4039
Well, turns out, I'm just an idiot. I put this together late at night and wasn't paying attention to the kind of tape I was using. I put duct tape on the back of the exposed pot and that was what was causing the issue. I rewrapped the pot in electrical tape, and now everything works!
another thing to check is whether your your jacks might be shorting out to the case when your audio cables are plugged in. do you lose the sound when the jacks are mounted to the box? or only when you close the box?
The audio cuts out if the metal of the jacks or cables are screwed into or touching the enclosure (first picture). But as long as they are free of the enclosure (the second picture), everything works.

IMG_3819.jpeg
IMG_3820.jpeg
 

thedwest

Active member
Don't trust the tape to insulate the pots, trimmed leads can easily poke thru. Use actual dust caps or cardboard. You can install a dust cap on a dual pot, but it needs to be trimmed a bit. The parts in the sockets, are they in tight? Those sockets are made for IC leads which are larder diameter than transistor leads. A thin coating of solder on the leads will fatten them up a bit. Clean the board and inspect the solder joints.
I'll try shimming some cardboard in and adding solder to the parts in the sockets. They aren't in there super tight but enough that they dont seem to fall out.
 

thedwest

Active member
I'll try shimming some cardboard in and adding solder to the parts in the sockets. They aren't in there super tight but enough that they dont seem to fall out.
I added cardboard and added solder to the parts in the sockets. Everything is now closed up in the box and works as it should. I think the exposed dual pot must have been the culprit. That plus the loose socketed parts. Thanks so much for the help!! Now I can add it to the build reports.
 

Grayscale

New member
So I get 9v going into the diode and .03v on the other end, the .03 persists down the chain. I’ve got the diode installed with the corresponding stripe on the board and aligns with photos I’ve seen but .03 seems strange.
 

Chuck D. Bones

Well-known member
Does the diode get hot? If you have more than a 0.3V drop across that diodes, then it's blown. You probably have (or had) a short between the 9V rail and ground on the cathode side of the diode. You can test the diode in-circuit with the power disconnected and the pedal switched to bypass.
 
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