Need some quick help with my Big Muff

[Cenzoru]

That Sustain pot behaviour seems to me like a Log pot (not Linear) without R1..
(mute at full CCW with very "low" responce a about 1/3 of initial wiper travel..)

Exactly, but I'm pretty sure that sustain is a 100K Linear pot (see attachment). Only the volume pot is a 500K Log Pot. I'll change the sustain pot, who knows, maybe it has some manufacturing issue.

[antonis]

Befor Pot change try to "simulate" its lower settings with a resistive voltage divider of same total resistance value..
(i.e. for an about 20% adjustment use 82k & 18k respectively, for 33% use 68k & 33k, etc.)

[duck_arse]

a slap on the wrist for antonis! why didn't you say "why have you left-right mirrored your build?" or "what transistors are you using?" and you didn't even mention the curse of the purple wire.

and, antonis, no welcome?

welcome to the forum Cenzoru.

[antonis]

 

Is there any amount of apologies enough for excuse, Stephen..??
(written by hand - not copied-pasted, of course..)

[duck_arse]

it is not for me to say, Antonis. you are at the mercy of Cenzoru.

[Cenzoru]

Befor Pot change try to "simulate" its lower settings with a resistive voltage divider of same total resistance value..
(i.e. for an about 20% adjustment use 82k & 18k respectively, for 33% use 68k & 33k, etc.)

I'm a total noob on electronics and this is my first pedal.( also this being the explanation about mirrored vero board).
I tried some measuring: resistance between pin 1 and 2 = for example at 1/4 of a full turn and it shows 25k and between pin 2 and 3, 75k at the same position, and so on.
Is that what you meant by "simulate"  ?
I did the measurements without connecting the pedal to 9v. Is that ok ?

[Cenzoru]

Got it  . All the transistor were reversed  . Maybe because of the mirrored built.

I read the debugging section and found that NPN transistor must have its base higher than its emitter. In my case was the reverse. So I reversed the position of the four transistors.

Thx a lot to all of you.

[duck_arse]

Cenzoru - wait, don't go just yet. it is often we get people misinterpreting vero layout convention. they are most often shown looking down on the top of the components, imagining the board is transparent. and then if the underside of the board is shown for the cuts placements, the builder needs to be aware of whether it is looking at the copper side, or still looking thru the transparent board from above.

and so we get mirrored builds. most common is the left-right mirrored, which in general doesn't affect transistor orientation, but makes a real mess of IC's. so, to my point - you transistors should not have been reversed. what transistors did the build specify, and what transistors did you build with? [the 2nxxx series transistors are backwards to the BCxxx series.]

and, because we always ask, can you post the transistor voltages now that the board works, please?

[Cenzoru]

what transistors did the build specify, and what transistors did you build with? [the 2nxxx series transistors are backwards to the BCxxx series.]
and, because we always ask, can you post the transistor voltages now that the board works, please?

The part list of the scheme specifies (see scheme below):
Q1 - BC550C
Q2 - BC550C
Q3 - BC550C
Q4 - BC550C
I used BC550C in every position (see photo below).


Transistor voltages:
Q1
C =4.24
B =0.66
E =0.06

Q2
C =4.22
B =0.66
E =0.06

Q3
C =4.28
B =0.66
E =0.06

Q4
C =4.88
B =0.66
E =0.06

Is that ok ?

Anyway thx a lot. I feel so enthusiastic with this. For sure you remember your first pedal.

[mth5044]

You should probably name it after the Duck's Arse       never forget...

[duck_arse]

Q4
C =4.88
B =0.66
E =0.06

well now, see those two resistors, R7 (470k) and R3 (100k) on the base of Q4, we would expect to see about 1V5 on the base there.

also, are those tayda transistors, by any chance?

@ mth - you might be thinking of elephants.

[Cenzoru]

this is the transistor info from the local store I bought:

NPN 45V 0,1A 0,5W B:420-800 TO92

Technical Specifications
• Collector Emitter Voltage At Open Base: 45V
• Collector Current: 0.1A
• Power Dissipation: 0.5W
• Transition Frequency: 100MHz
• DC Current Gain: 420...800

I don't think they are tayda transistors.