My effect works for about a minute then quits....

[mikestahlme]

I clipped the negative lead to ground like before and tested with the effect bypassed, on, and after it quits. C5 is rated for 50V and C11 is rated for 35V.

C5
Bypassed (effect working):
Positive = 6.33V
Negative = 0V

On:
Positive = 5.98V
Negative = 0V

After it Quit:
Positive = 5.94V
Negative = 0V

C11
Bypassed (effect working):
Positive = 2.72V
Negative = 0V

On:
Positive = 2.63V
Negative = 0V

After it Quit:
Positive = 2.61
Negative = 0V

[R.G.]

I am very confused. I can only find a C5 in the GGG schematic for wiring. I don't see it in the pedal schematic.  I see a C5 in the mods schematic, but it's 0.1uF. I see a c10 and a c11 that are 100uF.

Which cap is which, on which schematic?

I *think* you have a power problem, as the voltages on the two caps appear to be the incoming "9V" and the bias voltage. But they are much lower than they should be.

It's not possible to tell what's going on until I know what cap is what and which number on which schematic.

[mikestahlme]

You're right, C5 is missing from GGG's schem. I think the mods schematic is actually a schematic of 1/2 of the actual King of Tone, since it's basically just 2 modded BB's anyway. There's a bunch of part values in that schematic that are different than the GGG version and are not mentioned in the mods done to the pcb.

I am not using the mods schematic at all for that reason.
The only schematic I'm using is the GGG true bypass schematic, the pcb layout schematic, and the image of the mods done to the pcb (along with the changes listed left of the image.)

C5 is supposed to be 47uf electrolytic. I'm using a 100uf electrolytic until I get a 47uf.
C6 is on the schematic, but not labeled.
C10 is 0.1uF (non polarized)
C11 is 100uF electrolytic

I drew C5 on the schematic and labeled C6
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

[mikestahlme]

I drew C5 on the schematic and labeled C6

[R.G.]

You're right, C5 is missing from GGG's schem. ... I am not using the mods schematic at all for that reason.
The only schematic I'm using is the GGG true bypass schematic, the pcb layout schematic, and the image of the mods done to the pcb (along with the changes listed left of the image.)

C5 is supposed to be 47uf electrolytic. I'm using a 100uf electrolytic until I get a 47uf.
C6 is on the schematic, but not labeled.
C10 is 0.1uF (non polarized)
C11 is 100uF electrolytic

I drew C5 on the schematic and labeled C6

AH. Thanks. That helps.

You have a power/bias voltage problem, at least.

You said earlier that the voltage on pin 8 of the opamps was 8.79V. According to the schematic, this must be equal to the sum of the voltages across C5 and C11. Furthermore, if all is working well, the voltages on C5 and C11 should be almost equal. Since you're measuring the C5 voltage to ground, this means that the "9v" power is dropping to about 5.9-6V. The top of C5 and pin 8 on the opamp should be connected by a wire.

So the question now is - does the opamp pin 8 drop to 6V, too? If so, you either have a nearly exhausted battery or a circuit mistake pulling lots of current. If not, there is a problem in that they're not connected like they should be.

[mikestahlme]

The top of C5 and pin 8 on the opamp should be connected by a wire.

Could you please explain? What do you mean by "the top of C5"?

I tested it again with a brand new battery. The effect wasn't working, so I couldn't get any readings for that.
C5:
After it quit:
Positive (on) = 8.86V  (8.82V when bypassed)
Negative = 0V

C11:
After it quit:
Positive = 4V   (4.02V when bypassed)
Negative = 0V

IC
Pin 8 = 8.81V (same when bypassed)

[R.G.]

Could you please explain? What do you mean by "the top of C5"?

Sorry. Techie slang for "the most positive point" or the + lead.

I tested it again with a brand new battery. The effect wasn't working, so I couldn't get any readings for that.
C5:
After it quit:
Positive (on) = 8.86V  (8.82V when bypassed)
Negative = 0V
C11:
After it quit:
Positive = 4V   (4.02V when bypassed)
Negative = 0V
IC
Pin 8 = 8.81V (same when bypassed)

OK. Well, that means that all we've found and fixed is a weak battery.  Rats. Thought I had it there.

With the info at hand, there is once again no definitive answer. We're left with the usual suspects: (1) wrong component value or orientation (2) bad solder joints (3) bad wiring or (4) oscillation.

What happens if you temporarily short pins 1 and 2 of the opamp, and the diode-ends of R10 and R11?

[mikestahlme]

I shorted pins 1 and two, and at the same time shorted R10 and R11 together at the diode ends of each. It was very noisy and the guitar signal was quieter than usual. I could get some light od if I cranked the gain up and played hard.
then it quit again.

my diodes are germanium, would overheating them cause this problem? I have the same ones in silicon that I can try.

[R.G.]

I shorted pins 1 and two, and at the same time shorted R10 and R11 together at the diode ends of each. It was very noisy and the guitar signal was quieter than usual. I could get some light od if I cranked the gain up and played hard.

The shorting was an attempt to bypass a lot of the passive components and convert it into a near-unity-gain circuit just to see if it would continue to work. I'm guessing that you did your shorting by hand. If you had temporarily tack-soldered on a bit of wire in both cases, the noise would not have been there, I think. But in any case...

then it quit again.

Obviously, this didn't bypass the failing part, though.

my diodes are germanium, would overheating them cause this problem? I have the same ones in silicon that I can try.

Probably not. In any case, the shorting test took them out of circuit entirely, so if they were the problem, it would not have quit again.

It is possible that the gain pot or tone pot is going open, or that there is still a solder problem lurking in there, or that (most unlikely of all, but possible) that the opamp is damaged.

For such a simple circuit, from here it's probably simpler and quicker to remanufacture it. Clip out the opamp from the component side, then use your soldering iron to lift out the pins one at a time. Heat the pads on the solder side with your soldering iron and poke a wooden toothpick into the hole to clear it while the solder is liquid. Once that's done, get out your multimeter and check the resistance from lead to lead on each component. Every cap should show open circuit except C2, 4, 8, and 9, which are paralleled by resistances. Each resistor should show close to its nominal resistance. Correct any issues. Reinspect the soldering (sorry, yes, again) and wiring. Use your meter to verify that that the controls do in fact show resistance variation from the PCB back to the PCB when turned, on both sides of the pot. This tests the pot wiring and the pot wiper connection.

Be careful with the soldering iron. If you heat pads too long, they loosen from the board material.

[mikestahlme]

I'm about to do what you instructed above, but I thought I'd mention that I did solder the wires I used to temporarily bypass the diodes.
the effect usually makes that noisy static sound right before it quits.

[R.G.]

OK. That's even another vote for remanufacturing. There is some demon hidden in there. In spite of how casually we've approached this, we have eliminated the vast majority of simple defects. If we hungered and thirsted for knowledge, we could go ahead and track the demon down and kill it, but I suspect you'd rather have your pedal work.

[mikestahlme]

Good news! I started from scratch with a new board and built the original GGG project without doing the mods. It seems to be working perfectly. 

Now I guess I'll rebuild the original board, test it, then redo the mods if it works.

[R.G.]

That is good news. Congratulations.

Bad luck running into a difficult bug on the first one.

[mikestahlme]

I have both boards running in the same box. I did all the mods except the part replacements. I wanted to try playing it after each time I replaced a part. I did this once with R2, changing it from 4k7 to 27k, and the effect didn't work. Should I  do all the part replacements then try it out?

[StereoKills]

If you do all the replacements at once, how will you know what changed the sound in what way, or if the effect doesn't work - where the problem is?

[mikestahlme]

That's exactly what I was thinking, but it was working without the part changes, and as soon as I changed R2 it didn't work.

[mikestahlme]

Ok it started working after I changed C7 from 0.22uF to 0.1uF. It doesn't really sound different other than that the tone is a tiny bit fatter sounding. I think I'll leave the other board with the unchanged parts.

Thanks so much for all the help

it sounds amazing!
THANK YOU

[R.G.]

That's exactly what I was thinking, but it was working without the part changes, and as soon as I changed R2 it didn't work.

Ok it started working after I changed C7 from 0.22uF to 0.1uF. It doesn't really sound different other than that the tone is a tiny bit fatter sounding. I think I'll leave the other board with the unchanged parts.

This tells me that there are still hidden issues, possibly layout related. Neither changing R2 nor C7 should cause it to quit, unless it's doing something to make it oscillate at some unhearably high frequency.

[mordechai]

Just out of curiosity -- since on the TS808 a reduction of the 4.7K series resistor to ground increases gain...where is the corresponding resistor on the BB schematic that, when reduced, increases gain a bit?  Or is this circuit such a different beast that there is no corresponding resistor carrying this function?

[amptramp]

Just out of curiosity -- since on the TS808 a reduction of the 4.7K series resistor to ground increases gain...where is the corresponding resistor on the BB schematic that, when reduced, increases gain a bit?  Or is this circuit such a different beast that there is no corresponding resistor carrying this function?

The corresponding one would be R7 - but you have a strange connection where you have two resistors and two capacitors in series: C6, C7, R7, R8.  Changes to R7 and R8 have the same effect.  You could combine these into one resistor of 9.4K and one capacitor of 0.11µF.  You should note that this circuit uses an inverting amplifier whereas the TS uses a non-inverting amplifier that lets some of the original sound through at a gain of one even when clipping.  Therefore, the two circuits do not behave similarly - this one remains at the clip level when the signal is clipping.