Problem with Sabotage build

[dalanglois]

Hello!
I’m on my second pedal build from a Pedal Parts & Kits kit with all the supplied components. The first one was the NostalgiTone Spring Reverb and it was a success. I’ve now assembled the Sabotage v2 kit (not 2.1), and I’m getting a sound that “sputters” and “farts out.” There’s tons of gain, but the controls do seem to affect what they’re supposed to. I’m also hearing an oscillation or a kind of warbling on certain notes.

I’ve double-checked all the components to make sure nothing was installed incorrectly, and I’ve carefully inspected the board for possible shorts or open circuits, but I can’t find anything. Swapping the JFETs in their sockets does change the sound, but the issues remain. I have a bunch of J201s on hand, and I know they’re not supposed to bias correctly in this circuit, but in my case they seem to make the pedal almost usable, at least by ear.

What could I check to make sure the 2N5485s are working properly?

Thank you!

[Billy]

Post some nice clear in focus images of the component side of the pcb so that all component values and orientation can be clearly seen and offboard wiring traced

It does sound like a mis biased transistor what transistor are you using in the Q1 position

[dalanglois]

Output jack was reverse wired hence the shrink tubing and color change. Q1 is a BC550.

[Crumpred]

C8 & C12 look to be reversed. Never mind … Just read the red amendment on the build document.

[dalanglois]

Hi! Thanks for having a look!

I read in Build doc for v2 specifically asks to reverse C8 and C12 from the silkscreen layout. Was corrected in v2.1.

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[Billy]

All your components I can see look to be the correct value and orientation

What voltages do you get on all transistor pins Q1 EBC and Q2 to 6 DSG take voltages with the range pot fully clockwise

I’d suspect a mis biased transistor from your fault description

Fets as you’ll know are all over the place even from the same batch the fact it changes when you swap them around could indicate a biasing problem it could be anything from a poor solder joint on a biasing resistor to a transistor not fully secured in its socket

[dalanglois]

Hi! Thank you for your time!

Here are the transistor voltages :
Q1 : 1.29V , 1,88V, 5,43V
Q2 : 8.19V , 5.82V , 3.9V
Q3 : 5.6V , 0.24V , 0V
Q4 : 8.18V , 4.14V, 0.5V
Q5 : 2.77V , 1.17V, 0V
Q6 : 8.18V , 4.3V , 3.7V

[Billy]

Q1 looks OK that’s the treble boost / naga viper ish part

Q3 and 5 look off to me but unfortunately I don’t have the circuit on hand to check voltages

That’s assuming your readings are EBC Q1 and DSG pin order for Q2 to 6

I’ve probably confused that a bit Q1 pins top to bottom are EBC, Q2 to 6 top to bottom are GSD

Check C8 and 12 negative sides have continuity to ground

Are the fets 2N5485s

[Author]

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