Germanium 4 Big Muff issue

[Marbles]

Hi everyone!

First of all Happy New year (is that allowed still??). Hope everone is well. Saw Zach post some new layouts, awesome to see there are still new things being posted!

I hope someone might be able to help me, since I'm a little over my head. someone I know has a Germanium 4 "Big Muff" with one side not working. I offered to have a look and already said: If it's not an issue with a pot or anything, I probably won't be able to help, but I opened it up anyway. Not sure if anyone is familiar with the circuit? On freestomboxes there is a handdrawn layout I tried to follow.

I have probed a bit and the issue is at the end of the circuit I feel. There is an R26 with clear loud sound, but after that the volume drops considerably.

I took my multimeter out and started measuring. Not sure if its my multimeter, but measuring SMD parts is kind of tough for me. Most of them have a correct reading.

I know this is hard without visuals, so I will show where I'm at :D



What I dont really understand is: Lots of sound on that green circled R26. Almost no sound at the R27. I marked the point where no sound starts with the cross. I measured that one and it gives a proper 10k reading however. All the resistors do. The R29 on the left of that (underneath the arrow), I can't get a reading.

Could a resistor failing in this position cause a volume drop? Or should I be looking at the capacitors in the path from this point on? I have no experience with replacing smd, so I'm trying to rule out as much as I can :D

Hope someone knows if I can be more precise in my hunt!


The drawn schematic on the (public thread) would be here:

https://www.freestompboxes.org/viewtopic.php?t=20612

[rocket88]

I just took a look at the posted schematics, which are unverified, at I would venture to say that based on what you found check the solder connection on the other end of R26, and pull it out to test. It could be more than R26, but if signal is good up to that point, but after that it's not that could be the culprit. It could be the IC, but not sure.

[Marbles]

Thanks so much for replying!

I will have to desolder my first SMD component then :D Wish me luck ;)

[Marbles]

One more question if I can (to try and understand it a bit more):

If the schematic would be correct:

I have sound on both sides of R26. It measures correctly as well. I would assume it's ok.

R27 also measures ok. If my signal goes from R26 to R27, why don't I have sound on one side of R27? What am I missing in my simplified way of thinking? :D