Twin Face issues

[jwyles90]

Hey all,

Just put together a Twin Face build recently and while it technically "works", it's making some weird noises in the process. The silicon side is super noisy, and has a decent amount of hiss in the noise floor. For both silicon and germanium, if my guitar volume knob is at anything less than 10 there's basically no signal that comes through, and if I roll the volume all the way down on the guitar it just makes this loud buzzing noise instead of no noise at all. I thought initially it might be the guitar itself, but I tried it with multiple and the issue was present each time. I also noticed that it does something similar with my guitar tone knobs. Rolling them down to zero actually makes the signal sound more intense somehow, while anything in between doesn't seem to have a discernable difference from 0 to 10.

Any thoughts on what could be causing this? I know that fuzz faces can be kinda finicky at times, but this feels a little too finicky...

 

[Cybercow]

It's been a few weeks . . .. . have you solved this yet?

 

[jwyles90]

It's been a few weeks . . .. . have you solved this yet?

Unfortunately no. I tried everything I could think of, swapped out the silicon transistors, reflowed anything that looked sus and it still was doing the same thing. I put it into my drawer of unfinished projects to give it time to think about what it's done for a bit.

 

[music6000]

Unfortunately no. I tried everything I could think of, swapped out the silicon transistors, reflowed anything that looked sus and it still was doing the same thing. I put it into my drawer of unfinished projects to give it time to think about what it's done for a bit.

You made a big mistake putting that 072 Op Amp in, It's should be a TC1044SCPA!!!
I didn't even look at that first time around & everybody else missed it too!!!

 

[jwyles90]

You made a big mistake putting that 072 Op Amp in, It's should be a TC1044SCPA!!!
I didn't even look at that first time around & everybody else missed it too!!!

Yea I missed it initially as well, there was one hiding out in my bag of TC1044s for some reason. Probably should’ve put an updated picture on there, I swapped out the 072 for the correct chip fairly early into my troubleshooting journey.

 

[music6000]

Yea I missed it initially as well, there was one hiding out in my bag of TC1044s for some reason. Probably should’ve put an updated picture on there, I swapped out the 072 for the correct chip fairly early into my troubleshooting journey.

The other thing to look at is, are the Transistors NPN & PNP & put in the correct pins ???

 

[jwyles90]

The other thing to look at is, are the Transistors NPN & PNP & put in the correct pins ???

Yea I'm pretty sure they were in there the correct way. The germanium threw me for a loop initially with a wonky pinout, but once I figured that out it wasn't an issue. I don't think it was the pinouts either since I could get sound out of both sides, but only with my guitar volume knob all the way up. All the way down and I would just get this weird ground hum type sound. Anything in the middle on my guitar's volume and the signal was either super weak or just not there. Which is very strange...

 

[Cybercow]

Were you ever able to check the leakage on the Ge BJTs? From where did the Ge BJTs come?

 

[jwyles90]

Were you ever able to check the leakage on the Ge BJTs? From where did the Ge BJTs come?

I don't have a tool for checking leakages (unless there's a way to do that on a DMM?). I got them from either Amplified Parts or Guitar PCB, so I feel fairly confident that they're legit since I haven't had any issues with either of their stuff before. I was able to pop them into a Sunflower Fuzz Face build I had. They work and sound great in that build.

 

[Cybercow]

I don't have a tool for checking leakages (unless there's a way to do that on a DMM?). I got them from either Amplified Parts or Guitar PCB, so I feel fairly confident that they're legit since I haven't had any issues with either of their stuff before. I was able to pop them into a Sunflower Fuzz Face build I had. They work and sound great in that build.

OK. With the Ge BJTs from reputable sellers, it's beginning to appear that perhaps there is an incorrect value of one (or more) of the support (passive) components. Dbl-check the values of the resistors and caps. But first, without the transistors in their sockets, check the voltages around the board and ensure that they are correct in both Ge & Si modes. (Remember to toggle the switch for each section when testing.) We want to ensure that the correct voltages are being distributed around the board. Dbl-check the voltages around the chargepump especially.

To check the leakage on the Ge BJTs, you follow the instructions in this GeoFex article. Take your time and read it thoroughly. Note that for this method to work, the DMM must have at least a 10M Ω input impedance. (Check your DMM manual for that.)

 

[jwyles90]

OK. With the Ge BJTs from reputable sellers, it's beginning to appear that perhaps there is an incorrect value of one (or more) of the support (passive) components. Dbl-check the values of the resistors and caps. But first, without the transistors in their sockets, check the voltages around the board and ensure that they are correct in both Ge & Si modes. (Remember to toggle the switch for each section when testing.) We want to ensure that the correct voltages are being distributed around the board. Dbl-check the voltages around the chargepump especially.

To check the leakage on the Ge BJTs, you follow the instructions in this GeoFex article. Take your time and read it thoroughly. Note that for this method to work, the DMM must have at least a 10M Ω input impedance. (Check your DMM manual for that.)

That's super helpful, thank you! I'll have a look at that article too.

Life's been busy for me lately between work and going back to school and all of that, so I might not have time to take a whack at it for a little bit but that definitely helps to give me something concrete to look for. I suspect it might be something related to the charge pump as well too, since it almost behaves as if it's not getting enough electricity (but not in a cool fun way) when I've got the volume rolled back.

 

[jwyles90]

OK. With the Ge BJTs from reputable sellers, it's beginning to appear that perhaps there is an incorrect value of one (or more) of the support (passive) components. Dbl-check the values of the resistors and caps. But first, without the transistors in their sockets, check the voltages around the board and ensure that they are correct in both Ge & Si modes. (Remember to toggle the switch for each section when testing.) We want to ensure that the correct voltages are being distributed around the board. Dbl-check the voltages around the chargepump especially.

To check the leakage on the Ge BJTs, you follow the instructions in this GeoFex article. Take your time and read it thoroughly. Note that for this method to work, the DMM must have at least a 10M Ω input impedance. (Check your DMM manual for that.)

I'm looking at that article now. Sorry if this is a silly question, but would I basically solder wires from the bottom of a socket to a 9v clip and the two separate resistor leads? Then socket whatever transistor I'm trying to test?

 

[Cybercow]

I'm looking at that article now. Sorry if this is a silly question, but would I basically solder wires from the bottom of a socket to a 9v clip and the two separate resistor leads? Then socket whatever transistor I'm trying to test?

Yes. And yes. Just like it shows in the article.

 

[Cybercow]

That's super helpful, thank you! I'll have a look at that article too.

Life's been busy for me lately between work and going back to school and all of that, so I might not have time to take a whack at it for a little bit but that definitely helps to give me something concrete to look for. I suspect it might be something related to the charge pump as well too, since it almost behaves as if it's not getting enough electricity (but not in a cool fun way) when I've got the volume rolled back.

Same here. I may not respond the same day because life is all around me. But I keep coming back to check.

 

[jwyles90]

Same here. I may not respond the same day because life is all around me. But I keep coming back to check.

I appreciate that! That's one of the many reasons why this forum is so damn awesome. I'll be sure to keep y'all posted when I make more progress on it.