SOLVED Tone Vendor MKII Enigma...

[Coda]

Just completed the Tone Vendor MKII build. I plugged it all in, and got nothing. Bypass tone was fine, LED was on, but no fuzz...just a very high-pitched whistle...like something a dog could hear. After about 2 hours of checking and re-checking everything, I finally got sound. However, it sounds like the fuzz is on 5...even though the fuzz control is maxed.

It seems that after poking around (I literally was just pressing my finger against the board...especially around where the fuzz control/output ground/9v hooks up), it just came on. Is this a bad connection? What would make the fuzz control useless, while delivering a half-assed fuzz? Should I just chuck this build in the ocean and start over?

 

[Mcknib]

Your R3 looks like a 22K last band looks orange unless it's the glare if it's red red red then it's the 2K2 you said you'd put in

 

[Coda]

Your R3 looks like a 22K last band looks orange unless it's the glare if it's red red red then it's the 2K2 you said you'd put in

That was the value suggested to bias the transistor. Maybe I put it in the wrong place?...

 

[Mcknib]

R3 in your image is R5 in the pedalpcb schematic I think comes off the collector of Q2

Steve at smallbear would have selected those biasing resistors based on the hFE and leakage of your transistors

So you've currently got a 100K in R5 where they're saying you should have the 22K for correct bias

Its understandably confusing because 100K in R5 is correct in the ppcb build doc
and just to make it a little more confusing R3 and 5 just happen to be swapped around so as said your R3 is ppcb R5 and your R5 is ppcb R3

 

[Coda]

R3 in your image is R5 in the pedalpcb schematic I think comes off the collector of Q2

Oops. So I probably have the bias resistors in the wrong place. Makes sense. I never though to compare the two schematics.

 

[Mcknib]

Easily done my heads hurting just trying to explain it without confusing it more

A weird coincidence they've used the same R numbers and swapped their positions 3 & 5 or is it 5 & 3 haha I'm retiring good night

 

[Coda]

Easily done my heads hurting just trying to explain it without confusing it more

A weird coincidence they've used the same R numbers and swapped their positions 3 & 5 or is it 5 & 3 haha I'm retiring good night

Thank you very much. This is my second build, and I'm kind of getting tired of learning new things, if you know what I mean. Thanks again. I'll swap them tomorrow and see how it works.

 

[Mcknib]

Your 91K and 8K2 are in the right place hopefully the weirdness stems from a misbiased Q2

A 22K where it is would have some affect on the output it's normally 470R so a wee bit bigger

 

[Coda]

I swapped the resistors around and I now have normal volume control. However, I still have no fuzz control. Interestingly, with the fuzz control off the guitar volume control acts as the fuzz control.

I wonder if the issue is the extra small 100k at R1. I was never to confident in those mini resistors.

 

[Chuck D. Bones]

Thank you very much. This is my second build, and I'm kind of getting tired of learning new things, if you know what I mean. Thanks again. I'll swap them tomorrow and see how it works.

Building stuff with germanium can be challenging. If you're looking for easy builds, stick to silicon.

Resistor physical size is unimportant, as long as it fits on the board, it will work as intended. Better recheck all your parts. Did you get all of the transistors in the right place? They are not interchangeable.

 

[benny_profane]

That also sounds like there could be a short somewhere. Did you check your connections after replacing the parts?

 

[Mcknib]

Might be a good idea to post pics of it now after your changes

Your guitar volume will interact with the fuzz that's normal most folks just set the volume and fuzz to where they want it and use their guitar volume to clean it up or max the fuzz

Most of the tb's I've made are fuzzy as hell if you're saying your fuzz pot doesn't do much I'd check C3 the + side looks like it's got a big blob of solder on it and it's not completely flowed onto the pad

Stick yer iron on it for 3 or 4 seconds till you get a nice flow obviously be careful you don't wanna start pulling pads off

I'd perhaps reflow any ball like joints you can see, they're usually dry inside after that I'd snip off as much of the component legs as you can you've got a few longish bits on the solder side

 

[Coda]

Building stuff with germanium can be challenging. If you're looking for easy builds, stick to silicon.

Resistor physical size is unimportant, as long as it fits on the board, it will work as intended. Better recheck all your parts. Did you get all of the transistors in the right place? They are not interchangeable.

I have quadruple-checked the transistors. They are good to go.

That also sounds like there could be a short somewhere. Did you check your connections after replacing the parts?

Funny you mention that. When I swapped R3 and R5 I moved the 22k resistor to R5, and put a brand-new 470R in R3...except I forgot to trim the legs. When I plugged it in the legs were shorting against he enclosure. Opened it up and fixed it, and it all seems ok now.

Might be a good idea to post pics of it now after your changes

Your guitar volume will interact with the fuzz that's normal most folks just set the volume and fuzz to where they want it and use their guitar volume to clean it up or max the fuzz

Most of the tb's I've made are fuzzy as hell if you're saying your fuzz pot doesn't do much I'd check C3 the + side looks like it's got a big blob of solder on it and it's not completely flowed onto the pad

Stick yer iron on it for 3 or 4 seconds till you get a nice flow obviously be careful you don't wanna start pulling pads off

I'd perhaps reflow any ball like joints you can see, they're usually dry inside after that I'd snip off as much of the component legs as you can you've got a few longish bits on the solder side

I'll post some pics later, and I will go back through and double-check the joints.

 

[benny_profane]

Now that you have eliminated the short to ground, is the fuzz control still not working properly?

 

[Coda]

Now that you have eliminated the short to ground, is the fuzz control still not working properly?

I doesn't control the amount of fuzz, which it should. Instead, it slightly alters the tone of the fuzz, kinda brightens the tone up. With the fuzz control on 0, the guitar volume works like the fuzz control should.

 

[Chuck D. Bones]

Something's still not right. The Fuzz control should have a huge impact on the distortion and sustain.

 

[Coda]

Something's still not right. The Fuzz control should have a huge impact on the distortion and sustain.

Forgive my ignorance as I’m still learning, but this fuzz control is a stand alone component, correct? It’s basically a resistor, and doesn’t rely on any other component to function, correct?

 

[benny_profane]

What do you mean by a 'stand alone' component? It is a variable resistor. Its role in the circuit is an emitter degeneration resistor. In common emitter BJT amplifiers, added resistance in this area decreases the gain of the transistor. Here, the circuit is wired so that there is also a feedback network connected to the base of Q2. This circuit has very few parts and they are all very interconnected—changing the resistance of the Q3 emitter potentiometer impacts more than just the gain of that transistor.

Since that potentiometer is not doing anything, it suggests that the Q3 emitter is shorted to ground and the potentiometer is taken out of the circuit.

 

[Coda]

What do you mean by a 'stand alone' component? It is a variable resistor. Its role in the circuit is an emitter degeneration resistor. In common emitter BJT amplifiers, added resistance in this area decreases the gain of the transistor. Here, the circuit is wired so that there is also a feedback network connected to the base of Q2. This circuit has very few parts and they are all very interconnected—changing the resistance of the Q3 emitter potentiometer impacts more than just the gain of that transistor.

Since that potentiometer is not doing anything, it suggests that the Q3 emitter is shorted to ground and the potentiometer is taken out of the circuit.

That's exactly what I was asking; if the pot was dependent on other components, i.e., could a change down the line affect its function. Its not that the Fuzz control does nothing. It slightly alters the tone. The fuzz on 10 is full spectrum, harsh, brash...basically what it should be on 10. When you roll the fuzz control off, while the tone smooths out slightly, the amount of fuzz is the same. With the fuzz control on 0 the guitar volume acts like the fuzz control.

I'll look over the Q3 connections and see if anything is amiss.

 

[benny_profane]

Just to clarify: The guitar's volume knob will have that behavior when the circuit is behaving properly. That shouldn't be an indication that anything is wrong. If the fuzz control is just changing tone/timbre and not the compression/saturation of the signal, then there is a problem.

It would be helpful to troubleshoot this if you provided updated pictures since you've changed a decent amount of things since the initial pictures were posted.

 

[Coda]

Just noticed from the large image that C7 is in backwards.