Help with Sunking 2, gain pot not making any gain...

[pauloman80]

I solved my first issue of no signal when the pedal is engaged, swapped out IC3 for that fix. (I actually found a whole bag of IC's still sealed in electrostatic bags, I think I killed the first ICs I put into this build which is why it wasn't working.)

Now my issue is the gain pot doesn't increase gain. Instead there's a slight decrease in volume, not really like compression I don't think, but still not correct. Tone and Volume work perfectly & cleanly. I'm still completely ignorant when it comes to the math of these builds, so be gentle.    Any ideas? Thanks in advance, you geniuses!

EDIT: I did true-bypass wiring as well as the Thick & Fat & Clip switchable mods.

[mgwhit]

Are you using PCB-mount pots or solder lug pots?  If solder lug I'd suggest maybe you miswired them, but if you're using PCB-mount pots that's highly unlikely.

I'm guessing it's an incorrect component value, but it could be a bad solder joint or even a short.  Post some good photos of both sides of your board so we can check those out.

And, unless you know all your voltages are right, go ahead and put up your IC pin voltages, too.  Good luck!

[pauloman80]

Are you using PCB-mount pots or solder lug pots?  If solder lug I'd suggest maybe you miswired them, but if you're using PCB-mount pots that's highly unlikely.

I'm guessing it's an incorrect component value, but it could be a bad solder joint or even a short.  Post some good photos of both sides of your board so we can check those out.

And, unless you know all your voltages are right, go ahead and put up your IC pin voltages, too.  Good luck!

Okay, finally had a chance to test my values. I triple-checked my solder points, everything's clean. Still getting signal through it, but there's still the *very* slight decrease in volume when I turn up the gain knob.

(I wish I understood the math of all this.)

IC1:
1=4.67
2=4.67
3=1.19
4=0.00
5=4.64
6=4.67
7=4.67
8=9.24

IC2:
1=4.70
2=4.67
3=4.61
4=-9.02
5=4.62
6=4.67
7=4.65
8=17.85

IC3:
1=9.24
2=5.31
3=0.00
4=-3.83
5=-9.02
6=4.47
7=4.34
8=9.24

[midwayfair]

Examine (and measure if you have to) every single resistor connected to the "dirt" half of the gain pot and IC1B. Those are the only things affected by the gain control. Your voltages are fine.

[mgwhit]

Okay, finally had a chance to test my values. I triple-checked my solder points, everything's clean. Still getting signal through it, but there's still the *very* slight decrease in volume when I turn up the gain knob.

...

IC1:
1=4.67
2=4.67
3=1.19
4=0.00
5=4.64
6=4.67
7=4.67
8=9.24

Actually, I think IC1 pin 3 looks low.  I would expect something closer to the values on pins 2 & 3.  I'm not sure if that would cause the problem you're having, but it's worth looking at. 

Photos!

[midwayfair]

Okay, finally had a chance to test my values. I triple-checked my solder points, everything's clean. Still getting signal through it, but there's still the *very* slight decrease in volume when I turn up the gain knob.

...

IC1:
1=4.67
2=4.67
3=1.19
4=0.00
5=4.64
6=4.67
7=4.67
8=9.24

Actually, I think IC1 pin 3 looks low.  I would expect something closer to the values on pins 2 & 3.  I'm not sure if that would cause the problem you're having, but it's worth looking at. 

Photos!

Oh, you're right. It should be about 3.8V. I don't know what would pull it down like that, though.

[pauloman80]

I checked Pin 3 again, still low. No idea why, you guys would know better than me. Would I address that by checking the values of the parts coming into it?

**EDIT: I checked R7 coming off Pin 7 of IC1, and I've got a 430k instead of 422k. I couldn't find any 422k resistors but still had 430ks, so I used that instead. Is that enough of a difference to cause the problem? Back to checking...

Pics...

[MarcFive]

The solder on R29 looks suspicious from my house.

[mgwhit]

**EDIT: I checked R7 coming off Pin 7 of IC1, and I've got a 430k instead of 422k. I couldn't find any 422k resistors but still had 430ks, so I used that instead. Is that enough of a difference to cause the problem? Back to checking...

Yeah, there may be a few dodgy solder joints from what I can make out in those photos.  R13 stands out from here.

But what are the color bands on your R7.  A Four-band 430K resistor should be yellow-orange-yellow-gold.  That third band looks like it might be brown for 430R instead of K.

That would explain the gain pot issue, but it wouldn't explain the weird voltage on IC1 pin3.  i would suggest reflowing the solder on that pin.  Can't tell if it's bad, but it's one of the few things that could explain an out-of-place voltage.  I checked all the resistors in that part of the circuit and they looked good.

Edit: Oh, and to answer your question, no a 430K in that R7 position (assuming that's what you really have) wouldn't matter a hill of beans compared to the specified 422k.  Those odd values in Klone circuits come from component measurements, not necessarily their spec, so the original value was probably 420K or 430K and the part was somewhere within the range of its 5% tolerance.

[pauloman80]

**EDIT: I checked R7 coming off Pin 7 of IC1, and I've got a 430k instead of 422k. I couldn't find any 422k resistors but still had 430ks, so I used that instead. Is that enough of a difference to cause the problem? Back to checking...

Yeah, there may be a few dodgy solder joints from what I can make out in those photos.  R13 stands out from here.

But what are the color bands on your R7.  A Four-band 430K resistor should be yellow-orange-yellow-gold.  That third band looks like it might be brown for 430R instead of K.

That would explain the gain pot issue, but it wouldn't explain the weird voltage on IC1 pin3.  i would suggest reflowing the solder on that pin.  Can't tell if it's bad, but it's one of the few things that could explain an out-of-place voltage.  I checked all the resistors in that part of the circuit and they looked good.

Reflowing solder joints is no problem, I'll give it a full examination on that.

You're right about R7, it's 430R currently. What the heck did I do? I pulled it from a bag labeled 430k, unless it's mislabeled. Ugh! I'll have to hit the electronics surplus store next week and try swapping that piece out. Thanks, I'll update next week.

[MarcFive]

That would explain the gain pot issue, but it wouldn't explain the weird voltage on IC1 pin3.  i would suggest reflowing the solder on that pin.  Can't tell if it's bad, but it's one of the few things that could explain an out-of-place voltage.  I checked all the resistors in that part of the circuit and they looked good.

R29 feeds to R2 which feeds into IC1 pin3. Looks like R29 end @ IC3 pin8 is not soldered.

[MarcFive]

PM me, I'll mail you the resistor. NC

[mgwhit]

R29 feeds to R2 which feeds into IC1 pin3. Looks like R29 end @ IC3 pin8 is not soldered.

R29 does look dodgy, but it also feeds every point in the circuit that is receiving ~4.5V (VB).

[MarcFive]

R29 feeds to R2 which feeds into IC1 pin3. Looks like R29 end @ IC3 pin8 is not soldered.

R29 does look dodgy, but it also feeds every point in the circuit that is receiving ~4.5V (VB).

Yep, I missed that fact.

[pauloman80]

PM me, I'll mail you the resistor. NC

I see what I did, I combined my 430k with my 430R. Gonna swap that out right now. I'll also reflow the solder on R29, that top pad does look dodgy.

Edit: SUCCESS!!! It was that darned R7. According to a local builder buddy of mine, I did the same swap on my first Klon build because he fixed it for me. Looks like it was the fault of my organization and failing to test my components before installing. Lesson learned. Thanks, guys!