Son of Ben - No Wet Signal

[khaymanr]

Hey guys, first time pedal builder here. I recently got the Son of Ben kit from Musikding, and after many issues with delivery, finally got my hands on it. Went to build it, and it just didn't work at all. Bypass works fine, but once the pedal is engaged, no sound from the guitar, just a horrible crackling noise.

I figured I probably fried my transistors with my bad soldering iron (and also I did connect them backwards, so I also figured that should be it). Went out, bought another iron, purchased another kit, and had a second shot at it. Still the same issue.

I've attached some pics from the second build, since it's a lot cleaner than the first one, and it's the one that (I think) should not be giving me any issues.

It feels like I'm doing something very wrong, but I don't know what else to check for anymore. Everything I checked so far seems to be in working order at least (the JFETs, the switch, trimpots, jacks...). I'm at a complete loss.

P.S.: I can add more pictures if needed, and thanks in advance for any guidance

 

[Bricksnbeatles]

Looks like you’ve got all 3 trimmers maxed out. Try setting them as recommended in the build doc. It would make sense that you’re not getting signal since the JFETS are all going to be totally misbiased it looks like.

 

[temol]

I know that picture is worth thousand words but here we prefer measurements..

Time to measure some voltages. Take the multimeter, set to DC Voltage, then - black probe to GND, red to marked points.

 

[khaymanr]

I had tried to bias Q1, 2 and 3 right after I finished building everything, but it didn't really change anything really. So Idk.

Measurements as of right now are:

Q1: 1.20V (maxed out trimmer)
Q2: fluctuating an awful lot between 1.30V and 3.00V
Q3: 1.28V (also maxed)
Diode: 8.84V

Also something I forgot to mention that might be important (or not): the LED doesn't really turn off, it just dims a lot, sometimes it flickers, all when it is off. When it's on, it's solid red as it should be.

 

[CheapSuitG]

Looks like it is missing a 10uF missing on the right side.

 

[temol]

C10 is optional, should not affect normal operation.

Is it the same when you desolder the LED? or desolder IN/OUT/GND/SW wires from main pcb?

 

[khaymanr]

Well, I desoldered the LED and the measurements are as follows:

Q1: 1.18V (maxed out trimmer)
Q2: fluctuating around 5.00V (closed trimmer)
Q3: 1.20V (also maxed)

Diode voltage unchanged.

Without the switch pcb wires:

Q1: 1.18V (maxed out trimmer)
Q2: fluctuating between 1.30 and 3.00V (closed trimmer)
Q3: 1.50V (also maxed)

Diode voltage unchanged.

 

[Flying]

What voltage are you getting on the polarity protection diode, D100? The Red dot on temol's diagram.

The solder joint looks a little 'lacking' on the topside. It's not looking too groovy on the bottom either

​

 

[khaymanr]

In all three measurements, 8.84V

 

[khaymanr]

I just took a better look at some of the solder joints that looked a little shabby, like flying mentioned, reflowed them, but nothing changed, measurements seem to be the same still...

 

[temol]

Hm.. I think a photo will be needed after all - show a close-up of the transistor adapter boards. It can be a board without a transistor, it's about the pinout.

 

[khaymanr]

There you go. As far as I understand from the schematics that should be the right orientation at least..?

 

[swelchy]

pinout seems oriented correctly

 

[temol]

Yep, it's correct. But there are different adapter boards available.
For example:



Remove Q2 + Q3 and measure the voltages. Then maybe remove Q1 and Q3 and do the same.
I've already verified resistors (visually, from the photo) - nothing suspicious.

Also - make sure there's Vcc voltage (8.84V) on pin 1 and 2 of each trimmer.
Then - measure Source voltages.