[SOLVED] This one got me (Bellum Fuzz MKII)

[pi.cast]

Hi folks,
A couple of weeks ago I finished a bellum fuzz mkii and although simple pedal, it kicked my ass in every way possible.
The first time I drilled the enclosure, it cracked.
Then when tried to paint the new enclosure, the clear coat got messed four times.

Now the pedal is assembled but it isn’t working properly.

To be fair, it is the first pedal pcb circuit not working at the first take, and I already checked for the usual suspects.

I get sound from it, but the signal is very weak in volume and there’s only very little fuzz which is really fizzy/hissy.

I’ve retested the solder joints for continuity and they seem ok.

I would bet my money on the transitors. Unfortunately I only had four 2N5088 left so I just used them without looking at individual/matched gains.

Did I have to look out for specific Hfe values? Should they be matched or selected for different gains?

Any other attention points for this circuit I should have cared for?

I don’t have a lot of experience with big muff style pedals (I understand this is where the fuzz war mkii is coming from).

Thanks a lot to anybody willing to help

 

[BuddytheReow]

Can we see the underside of the board to check your soldering? Since you'll have the board out you may want to clean it with IPA. You've got 5088s in there which are pretty stable so there's no need for matching. The way you're describing the problem it sounds to me like a bad solder joint somewhere.

Instead of waiting for others to chime in take a look at this https://forum.pedalpcb.com/threads/troubleshooting-101.9028/

 

[fig]

Of course there is a pot condom on that tone pot...

R12 is 100Ω?

This is awfully close as well.

 

[pi.cast]

Thanks for the suggestions!
Eventually, I managed to get it to work. It seems the legs of one transistor were slightly oxidized and not making proper contact in the sockets.
I've scraped them with an x-acto blade and everything started working correctly.
I discovered the problem with a component tester as the transistor was giving me a completely different reading on multiple tests.

R12 is 100Ω?

This is awfully close as well.

View attachment 18660

Yes R2 is 100ohm. I think the picture doesn't represent the color of the bands really well.
Good catch! The jack is really close to the enclosure casting, even though it wasn't touching. I will cover the contacts with some heat-shrink tubing for good measure.

 

[fig]

That's good news!

 

[almondcity]

nice looking pedal!