LectricFx Downtown - SubHarm pot not working

[aleximan]

Hello folks.
I am Aleks and I am a total noob in pedalbuilding with just a basic understanding and knowledge in el. components to put together a pedal kit.
I recently built a Downtown - octave multiplexer kit. The build is quite neatly soldered and meticulously put together following building instructions and the technical material.
Yesterday i tried it for the first time. Everything seems to work properly (sensi,tone,fuzz, bass, blend), except for the "SubHarmonic" pot that is completely mute/dead (no octave up or down, it does not have any effect while turning the pot).
I already spoken to Keefe from LectricFx who kindly suggested that I should seek help in this section and that Mr. Scruffie might be the right person to help me out in locating the cause of the issue.
I was hoping for some schematic of control points with voltages in order for me to be able to measure and locate the issue.
Also if anyone has any suggestions about what the cause of the unresponsive pot might be, help would be much appreciated.


Thanks in advance for feedback, best regards

Aleks

[Scruffie]

Mr Scruffie is going to request you post clear photos of the front and back of your PCB and voltage readings from all the IC's 

And a little question about your issue... do you get any octave down at all? Or just the SubHarmonic pot itself seems to have no effect?

[aleximan]

Hello,

Thanks for the fast feedback. 
Will try to provide all the necessery material a.s.a.p.

The SubHarm pot does no change, neither any harmonic effect is audible...like the whole segment is muted.

Thanks a lot.

A

[Scruffie]

Thanks 

Okay, just to say as you proclaim yourself pretty new to all this and it's a pretty common mistake, this is how you should order voltage readings.

[aleximan]

Hi Scruffie.

Thanks for the support. Yeah I am quite green in elctronics but I belive being quite a quick learner...one has to be these days.
It took me some time but I managed to measure all the voltages on the IC pins...and wrote the values directly close to each pin on the schematic... Keefe told me you are quite an ace solving these issues. I appreciate much your helpful instructions on where to look for the cause of the problem.

Pics and voltages that you requested:






I took pictures of both sides of the pcb as requested. If you need anything more detailed just ask.
Thanks a lot. 

A

[Scruffie]

Links aren't working for me, can anyone else confirm that's the case or is it my browser?

[aleximan]

I adjusted the links..something went wrong the first time. sorry 

[Scruffie]

IC11 has no supply voltage on pin 8 and no bias voltage on pin 2 or 3, fed from R83.

There's a problem around IC2 and the connected half of IC1 (pin 5, 6 & 7).

Check around those two areas on the board, I see a couple of suspect solder joints so a re-flow might be in order.

[aleximan]

Thank you for the help. I will do a meticulous check and re-flow tonight.
ty,
A

[aleximan]

Ok, so far I got some progress. I re-flew some connections in the IC11 group and now it has other voltages: pin 2 and 3 have 3.56V each, and the 8 has 9.04V. I believe this segment should be ok now.
I also re-flew some suspicious joints in the IC1 and IC2 area but when measuring again all values seem the same as before. I went thoroughly through all the nearby components involved (c3,c2, r5,r6,r7 and r10) and rechecked pins 6 and 7 of IC2 but no change. What values should I achieve on pins 5,6,7 of IC1?

thanx
A

[Scruffie]

If you remove IC2 from its socket, what voltages do you get on IC1, pin 5, 6 & 7?

[aleximan]

IC1 voltages when IC2 removed:
pin5 0.01V
pin6 0.01V
pin7 -0.15V

[Scruffie]

Okay... what voltages do you get on Q1 & Q2, both with and without IC2 inserted.

[aleximan]

With IC2:
Q1
E=7.41V
B=6.74V
C=7.42V

Q2
E=0.59V
B=-0.00V
C=-2.62V

_____________________

Without IC2:
Q1
E=0.00V
B=0.00V
C=-0.02V

Q2
E=0.00V
B=0.01V
C=-7.62V

[Scruffie]

I suspect your CA3080 is duff I'm afraid.