General Guitar Gadgets Klon Centaur giving me headaches for some years now

[santuka]

Hi, my name is Santiago. I live in Argentina and I've been into the DIY world from some years now. I'm a electronic engineer. Built a few pedals, all proudly working.

Some years ago I built a the Klon from GGG. It never worked so I throw it away and never look at it again. Now, with this social distancing stuff, I finally have some spare time to get back to my hobby.
I've been reading a lot and debugging my Klon, finding some things that where bad and corrected them. But it still doesn't work.

The problem is in the "high gain" part of it. I get the clear "boost" tone when gain pot is at 0. But as I increase it, the sound is dark, cleaner and volume decrease.
I'm truly lost. Here are my voltage readings:

IC1 TL072:
Pin 1: 4.6
Pin 2: 4.6
Pin 3: 1.2 (according to the ggg instructions this should be around 3.7, which makes me think there's a problem here)
Pin 4: 0
Pin 5: 4.6
Pin 6: 4.6
Pin 7: 4.6
Pin 8: 9.2

IC1 TL072:
Pin 1: 4.6
Pin 2: 4.6
Pin 3: 4.6
Pin 4: -8.8
Pin 5: 4.6
Pin 6: 4.6
Pin 7: 4.6
Pin 8: 16.8

IC3 7660:
Pin 1: 9.2
Pin 2: 4.6
Pin 3: 0
Pin 4: -4.3
Pin 5: -8.8
Pin 6: 3.2 (Acording to GGG info should be 5)
Pin 7: 4.5 (Acording to GGG info should be 7)
Pin 8: 9.2

Both pin 6 and 7 of the 7660 are not NC, so I figure even if I'm getting different values is not important.

Any help will be appreciated.
Stay safe!!

[Slowpoke101]

Welcome to the forum. There have been quite a few new members show up since this social distancing thing was started.

Now to see if we can help.

The low voltage reading on pin 3 of IC1 is most likely being caused by your meter loading the pin down. I think that on the GGG version pin 3 is supplied via a 2M2 resistor so a reading of 1.2V makes sense if your meter has an input impedance of 1M. All the other voltages are within usable levels and do not point towards a problem.

Is there any chance that you can upload a few pictures of your board (both sides ) and your wiring? As clear as possible please. This would be very helpful.

[Rob Strand]

There's are a number of schematics and layouts for the Klon and some have wrong part values.

Can I suggest you look-up the thread "Klon Centaur: the correct and final schematic"
on www dot freestompboxes dot com.

Compare your part values against the good schematic.


Please follow-up with Slowpoke101's requests as the part values might not be your main problem.

[santuka]

Welcome to the forum. There have been quite a few new members show up since this social distancing thing was started.

Now to see if we can help.

The low voltage reading on pin 3 of IC1 is most likely being caused by your meter loading the pin down. I think that on the GGG version pin 3 is supplied via a 2M2 resistor so a reading of 1.2V makes sense if your meter has an input impedance of 1M. All the other voltages are within usable levels and do not point towards a problem.

Is there any chance that you can upload a few pictures of your board (both sides ) and your wiring? As clear as possible please. This would be very helpful.

Ok, here are some pictures of it.









I know I know, is BY FAR not my best job on soldering and I kept resoldering things because there where shorts and bad connections. But now is all correct (or at least it appears to be).

Thanks for the replies, I will read your advice!

[bean]

The values in the GGG schematic appear to be the correct ones. Your R2 is not visible in the pics but as long as you have a 1M resistor there (and not, say 10M) then assume it's correct. The charge pump voltages may not be concerning either since the one that counts is what you get out of pin5, which for you is about -9v. So, assume that's all good too.

R8 looks like it might be 150k and not 1k5 but I can't tell for sure from the pic.
Those diodes look like 1n914 instead of germanium. Not that those won't work but it is worth pointing out.
Also, I can't really see the wiring on the dual gang pot but an error there would surely cause a problem.

Really, the easiest way to solve the problem is to audio probe the circuit. Turn the gain pot full CW and probe the following in order:
Where C3 and R6 connect.
Pins 5 and 7 of IC1B.
Where C10 and R16 meet.

What you are listening for is where in that chain of signal your output is getting messed up.

[santuka]

The values in the GGG schematic appear to be the correct ones. Your R2 is not visible in the pics but as long as you have a 1M resistor there (and not, say 10M) then assume it's correct. The charge pump voltages may not be concerning either since the one that counts is what you get out of pin5, which for you is about -9v. So, assume that's all good too.

R8 looks like it might be 150k and not 1k5 but I can't tell for sure from the pic.
Those diodes look like 1n914 instead of germanium. Not that those won't work but it is worth pointing out.
Also, I can't really see the wiring on the dual gang pot but an error there would surely cause a problem.

Really, the easiest way to solve the problem is to audio probe the circuit. Turn the gain pot full CW and probe the following in order:
Where C3 and R6 connect.
Pins 5 and 7 of IC1B.
Where C10 and R16 meet.

What you are listening for is where in that chain of signal your output is getting messed up.

OK, first of all Brian you are one of my, let´s say, chilhood heros. So, very glad you're answering!  Love your pedals and your page! I wanted to buy a PCB for the DMM but restrictions in Argentina for shipping where really bad at that time...and now is discontinued 

Regarding the pedal:
R8 is 1k5, double checked. Diodes are 1n60, germanium diodes. I've changed the pot making sure it was correctly connected. There was a moment when pressing down a cable on that pot gave what (I think) is the correct sound and gain. But I'm not sure if it was just luck or me messing up the pot with my fingers. That's when I changed the pot to be sure that wasn´t the problem.
I'll try the audio probe thing and let you know...

Thank you!!

[willienillie]

There appears to be a lot of loose bare wire around your footswitch, make sure there are no shorts there.

Also, probably more related, you have soldered wires into the rivet holes on the pots.  It has been my experience that doing so ruins pots, I think the flux wicks down between the solder lug and resistive track and kills that connection.  I would replace all of the pots, and solder only to the proper lugs or PCB pins.

[Rob Strand]

The values in the GGG schematic appear to be the correct ones.

Thanks for checking - I'll try to remember that.

[bean]

OK, first of all Brian you are one of my, let´s say, chilhood heros. So, very glad you're answering!  Love your pedals and your page! I wanted to buy a PCB for the DMM but restrictions in Argentina for shipping where really bad at that time...and now is discontinued 

Regarding the pedal:
R8 is 1k5, double checked. Diodes are 1n60, germanium diodes. I've changed the pot making sure it was correctly connected. There was a moment when pressing down a cable on that pot gave what (I think) is the correct sound and gain. But I'm not sure if it was just luck or me messing up the pot with my fingers. That's when I changed the pot to be sure that wasn´t the problem.
I'll try the audio probe thing and let you know...

Thank you!!

Well, that's praise I'm not sure I deserve but thank you And hey, it goes up the ladder - there are several of my personal DIY "heroes" on this forum, too (for lack of a better term. Maybe guru is appropriate (not for me)).

In any case, the audio probe is the second most important tool after the multimeter, IMO. I use both all the time b/c I am constantly f-ing up my own builds. Usually, those two tools and some thinkybrain time solves almost every problem.

[santuka]

There appears to be a lot of loose bare wire around your footswitch, make sure there are no shorts there.

Also, probably more related, you have soldered wires into the rivet holes on the pots.  It has been my experience that doing so ruins pots, I think the flux wicks down between the solder lug and resistive track and kills that connection.  I would replace all of the pots, and solder only to the proper lugs or PCB pins.

Well, I've been touching it these past days. And the problem is with the gain pot apparently. When I touch it or push it in certain ways it engage the real tone. It lasts a few moments until I touch it again and then the same problem appears. I changed the pot, changed all wires that connect to it, the problem persist. I soldered the new pot on the rivet holes, didn't read your advice in time. And that was my last dual gang 100K pot, which is a shame. I think you're right, I believe this is the problem, the pots get messed up when you solder them that way. I don't find any other explanation than that... Which is weird because it NEVER happened to me to be honest.

If I manage to make it work I will post pictures and audio samples of it.

Thank you for your help!

[santuka]

OK, first of all Brian you are one of my, let´s say, chilhood heros. So, very glad you're answering!  Love your pedals and your page! I wanted to buy a PCB for the DMM but restrictions in Argentina for shipping where really bad at that time...and now is discontinued 

Regarding the pedal:
R8 is 1k5, double checked. Diodes are 1n60, germanium diodes. I've changed the pot making sure it was correctly connected. There was a moment when pressing down a cable on that pot gave what (I think) is the correct sound and gain. But I'm not sure if it was just luck or me messing up the pot with my fingers. That's when I changed the pot to be sure that wasn´t the problem.
I'll try the audio probe thing and let you know...

Thank you!!

Well, that's praise I'm not sure I deserve but thank you And hey, it goes up the ladder - there are several of my personal DIY "heroes" on this forum, too (for lack of a better term. Maybe guru is appropriate (not for me)).

In any case, the audio probe is the second most important tool after the multimeter, IMO. I use both all the time b/c I am constantly f-ing up my own builds. Usually, those two tools and some thinkybrain time solves almost every problem.

Yeah! I've done what you suggested and that was what make me think maybe the pot was the problem! Audio probing is really good actually.
These two pedals are the best pedals I have, both designed by you!

Catalinbread Dirty Little Secret Clone (Don't know how you named it, maybe Grapevine? Can't remember haha!)



Deep Blue Delay Clone (Think you named it "Sea Urchin" or something like that) Paint job on this went to hell!



They are a little bit f-up because I made them long time ago and been using them ever since!

Thank you guys! Take care! 

[santuka]

All right! So I made it work!! 
It was the pot, as we all suspected. Too much heat when soldering makes those contacts get a little loose, weird but true.

Now is working, and here is the video to probe it as promised: https://www.youtube.com/watch?v=DMedI1tdcKU&feature=youtu.be

Thank you all for the support! I was inspired and I make an old phase 90 that I abandoned years ago work too! Turns out it was a CLEAR short beetween two TL072 pins I never saw (still can't believe it).
So Santiago 2 - Quarantine 0 so far!

Take care guys! And keep the good vibes!