Troubleshooting Shein Fuzz Companion

[bifbangpow]

Recently went back to look at a really old pedal I made with a kit. Gets clean sound but no sound at all when the fx is activated.
schematic: http://www.generalguitargadgets.com/pdf/ggg_secf_sc_bst.pdf
project: http://www.generalguitargadgets.com/effects-projects/fuzz-tones/shin-ei-companion-fuzz/

note: in the written instructions to this project it notes that the c8 c9 and c10 are marked differently in the diagram than on the board and to use the diagram not the pcb placement. ALSO it notes not to put in jumperwires. so I didn't.

no mods nor subs.

Voltage at the circuit board end of the red battery lead = 8.83
Voltage at the circuit board end of the black battery lead = 0

Q1:
C- 8.72
B- .45
E- 0

Q2:
C-7.74
B- .45
E- 0

Q3:
C- 6.4
B- .73
E- .09

D1
A  = 0
K  = 8.8

C1- .45
C2- .45
C3 - .45
C4- 8.58
C5- 0
C6 - 0
C7- 0
C8- 7.96
C9- .69
C10- 6.43
C11- 8.68

[antonis]

For a good  start, try to find out what's happening with 5 μA Q1 Collector current.. 
[(8.83 - 8.72) / 22k]

[bifbangpow]

How would one do that?

[antonis]

Probably by checking 22k correct value.. 

[bifbangpow]

did I @#$% up a resistor? let me see.

[bifbangpow]

the 22k looks like the right resistor to me.

[Mark Hammer]

"No sound at all" suggests that maybe something is installed backwards.
It appears you have a meter.  Set it to measure AC voltage.  If you have to set the range, set it for whatever is less than 10V.  With the power on, and your guitar plugged in, measure the AC voltage, when you strum, at the base of Q1, and at the collector of Q1.  You should see something around 20-50mv at the base, and maybe 200-500mv at the collector.

If that checks out OK, then look for the AC voltage at the Fuzz pot wiper, and at the collector of Q2.  The pot wiper should be something a bit less than what you got at the Q1 collector, and you should get something larger at the Q2 collector.

If none of those is checking out, consider the possibility that the transistors you are using have a different pinout than you thought.

[iainpunk]

i'd like to advice using an audio probe.



also, the collector voltages seem quite high, i echo Mark on the pinout thing
which transistors did you use for Q1 and Q2?

cheers, Iain

[aelling]

Check your wiring, your pots aren't wired like it's drawn in the GGG layout/wiring diagram.
http://www.generalguitargadgets.com/pdf/ggg_secf_lo.pdf

[bifbangpow]

"No sound at all" suggests that maybe something is installed backwards.
It appears you have a meter.  Set it to measure AC voltage.  If you have to set the range, set it for whatever is less than 10V.  With the power on, and your guitar plugged in, measure the AC voltage, when you strum, at the base of Q1, and at the collector of Q1.  You should see something around 20-50mv at the base, and maybe 200-500mv at the collector.

If that checks out OK, then look for the AC voltage at the Fuzz pot wiper, and at the collector of Q2.  The pot wiper should be something a bit less than what you got at the Q1 collector, and you should get something larger at the Q2 collector.

If none of those is checking out, consider the possibility that the transistors you are using have a different pinout than you thought.

Collector of Q1 measures 8V, and the base is 450mv.... now what?

[bifbangpow]

i'd like to advice using an audio probe.



also, the collector voltages seem quite high, i echo Mark on the pinout thing
which transistors did you use for Q1 and Q2?

cheers, Iain

I believe I used Transistor Fairchild NPN Low-Gain Silicon Dots, Hfe 10-50 but I built the board a long time ago and there are no markers on the dot.

[bifbangpow]

Check your wiring, your pots aren't wired like it's drawn in the GGG layout/wiring diagram.
http://www.generalguitargadgets.com/pdf/ggg_secf_lo.pdf

what the hell? how did i do this? what a nubskull. thank you

[bifbangpow]

ok New measurements and photos. Fixed the wiring but still having no sound when fx is active.

Q1:
C- 8.2
B- .43
E- 0

Q2:
C-7.5
B- .5
E- 0

Q3:
C- 6.2
B- .7
E- .0

D1
A  = 0
K  = 8.6

C1- .45
C2- .45
C3 - .45
C4- 8.58
C5- 7.5
C6 - 0
C7- 0
C8- 7.96
C9- .72
C10- 6.12
C11- 8.68

[bifbangpow]

Maybe I should replace y transistors with 2N3904s instead of the dots?

[willienillie]

I have an original FY-2 and will confirm that the transistors are indeed 2SC536.

[iainpunk]

well, those Fairchild dot transistors are to low gain to bias right in that configuration with such low collector resistors (R2 and R4), maybe swap them out with higher values, like 220k just to see what the bias change is, this cuts down on desoldering the transistors which may damage them, and resistors are cheaper than transistors.

cheers, Iain

[Rob Strand]

A point of confusion is (IIRC) there's two versions of the FY-2.  Germanium transistors fairly low gain.  Silicon transistors as per willinillie.    Low gain silicons wasn't one of the combinations.

[iainpunk]

well the Ge version is basically a fuzz face with some tweaks and a 2n output cap taking out all low end, the Si version is a rough interpretation of the FuzzRite. the nasty nature and amount of grit and gain is way higher with the Si version, compared to the Ge version.

cheers, Iain

[bifbangpow]

Alright. I'll pick up some 2Ns tomorrow and swap them out.

[Mark Hammer]

I have an original FY-2 and will confirm that the transistors are indeed 2SC536.

I'm not sure how this happened, but I have editted willienillie's post.  Weird.