Author Topic: Big Muff Pi Build (Green Russian) - Troubleshooting - No Sound  (Read 301 times)

ericlaw02

Big Muff Pi Build (Green Russian) - Troubleshooting - No Sound
« on: January 31, 2021, 04:22:15 AM »
Hi, noob here, I built a Green Russian Big Muff Pi, and I get no sound at all with the effect on (only bypass works).

Built with the layout from http://effectslayouts.blogspot.com/2016/05/electro-harmonix-big-muff-1590a.html, which corresponds to the Kit Rae schematic here (http://www.bigmuffpage.com/Big_Muff_Pi_versions_schematics_part3.html).

So far I can see the transistor voltages are completely messed up, but I have no idea why it's that way (no electronics background, only know how to solder :icon_redface:):

Power In: 9.13V
Q1: C=6.96V, B=7.7V, E=6.96V
Q2: C=0.87V, B=0.87V, E=0.26V
Q3: C=0.88V, B=0.87V, E=0.26V
Q4: C=0.88V, B=0.87V, E=0.26V

D1: A=0.63V, K=0.88V
D2: A=0.88V, K=0.63V
D3: A=0.62V, K=0.88V
D4: A=0.88V, K=0.62V

Reference transistor voltage for reference: (Q1, Q2, Q3, Q4 order in reverse versus compared to Kit Rae schematic)
http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf

I've gone through the board with a light and I couldn't find any bridges, tried wiggling everything for cold solder joints and still no dice.

antonis

Re: Big Muff Pi Build (Green Russian) - Troubleshooting - No Sound
« Reply #1 on: January 31, 2021, 06:52:16 AM »
Could you post some photos of your build..??
(both items and soldering PCB side..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

iainpunk

Re: Big Muff Pi Build (Green Russian) - Troubleshooting - No Sound
« Reply #2 on: January 31, 2021, 08:41:42 AM »
i have a strong suspicion that R10 R11 and R18 are the wrong values.
we need to see the pictures of the board to be sure tho

cheers, Iain
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail - snail man is fuccing real
『snailpilled』

ericlaw02

Re: Big Muff Pi Build (Green Russian) - Troubleshooting - No Sound
« Reply #3 on: February 02, 2021, 12:34:32 PM »
Hi, thank you both for your help!

Finally got to the taking the photos:
Component side: https://i.imgur.com/fLs5fir.jpg
Component side (with light underneath): https://i.imgur.com/KiuHRjz.jpg
Trace side: https://i.imgur.com/u9pRRSw.jpg

In-circuit resistance:
R10: 377 ohm
R11: 10.4k ohm
R18: 10.8k ohm

EDIT: Supplemented photo for the resistor hidden between the 103J & the transistor on the top left corner: https://i.imgur.com/u34Ozaw.jpg
EDIT2: Also supplemented mapping between component values and the schematic I did for debugging purposes: https://i.imgur.com/ZHmAtvR.jpg.
Also realized the photo doesn't show the transistor types, they are all 2N5088s.
« Last Edit: February 02, 2021, 12:46:23 PM by ericlaw02 »

antonis

Re: Big Muff Pi Build (Green Russian) - Troubleshooting - No Sound
« Reply #4 on: February 02, 2021, 01:19:18 PM »
Trace side: https://i.imgur.com/u9pRRSw.jpg

Don't get me wrong but that's unacceptable both for solder joints and tracks/pads etching..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Keeb

Re: Big Muff Pi Build (Green Russian) - Troubleshooting - No Sound
« Reply #5 on: February 02, 2021, 01:45:31 PM »
So it seems you have a solder bridge here
https://imgur.com/a/IrTddcS

There might be more but it's difficult to make sure from your photos. I would suggest audio probe or going over the pcb and checking continuity along the traces (and their neighbors!) to find any bridges/open tracks.