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
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?
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
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.
(https://cdn.sparkfun.com/assets/f/0/a/1/f/51c206efce395f0f0d000003.png)
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. :D
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:
(https://i.imgur.com/ePEw9Wg.jpg)
(https://i.imgur.com/foWK8SY.jpg)
(https://i.imgur.com/imA4ss9.jpg)
(https://i.imgur.com/ADJNY4x.jpg)
I took pictures of both sides of the pcb as requested. If you need anything more detailed just ask.
Thanks a lot. :)
A
Links aren't working for me, can anyone else confirm that's the case or is it my browser?
I adjusted the links..something went wrong the first time. sorry :(
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.
Thank you for the help. I will do a meticulous check and re-flow tonight.
ty, :)
A
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
If you remove IC2 from its socket, what voltages do you get on IC1, pin 5, 6 & 7?
IC1 voltages when IC2 removed:
pin5 0.01V
pin6 0.01V
pin7 -0.15V
Okay... what voltages do you get on Q1 & Q2, both with and without IC2 inserted.
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
I suspect your CA3080 is duff I'm afraid.
Ouch. :(
I ll try to find another on ebay to do the testing and hopefully make the pedal work a.s.a.p.
Thank you very much for all the support, Scruffie . Much appreciated.
I will let you know if the problem will be solved once the part is replaced.
Best regards. ty. :D
Aleks
Ouch. :(
I ll try to find another on ebay to do the testing and hopefully make the pedal work a.s.a.p.
Thank you very much for all the support, Scruffie . Much appreciated.
I will let you know if the problem will be solved once the part is replaced.
Best regards. ty. :D
Aleks
Ebay might not be the best place to find one...
Try asking in the parts jar sub-forum here.
Hello Scruffie.
I managed fo find a CA3080e in a vintage sinth parts shop online, it arrived via mail today and appears to be mint .
I replaced the component and took measurements on the pins of the Q1, Q2, IC1 and IC2 and found out completely different values compared to the ones with the old/duff IC.
Q1 : E_0.00V / C_0.00V / B_7.08V
Q2 : E_0.00V / C_0.00V / B_7.60V
IC1: p5_0.01 / p6_ 0.01V / p7_-015V
IC2: p1_0.00V / p2_0.00V / p3_0.00V / p4_7.60V / p5_7.08 / p6_0.01V / p7_9.00 / p8_-0,00
What do you think? Are these values closer to the ones that work?
Havent plugged it yet, wanted to hear your opinion first before "trying&frying" anything. :D
Thanks for your feedback.
br, A
Looks better, give it a try.
Hi Scruffie.
Tried the pedal after the component was replaced, but no success in solving the issue.
The blend, fuzz, tone and sensitivity pots seem to work fine although still no response from SubHarm pot (no audible octave / no chance while turning pot in any direction), also bass switch does not seem
to make any consistent change in sound, just a slight change in tone is perceptible. :(
I have remeasured all the values on IC pins and Transistors if you could find any clues or suspicious values... also checked all the soldering work for any cold joints and found just one anomaly that went unnoticed till now...there is a slight iron burn mark on CAP15 do you think this might have damaged the component and have a negative effect/ couse the SubHarm issue? Should I check the voltages on the cap to see if it still works fine?
Pics:
(https://i.imgur.com/jglgCol.jpg)
(https://i.imgur.com/gTCZAZe.jpg)
I am completely frustrated at this point. If you could give me any clue to check would be muck appreciated. Sorry for bothering you this much with the issue, I sincerely hoped it would work by replacing the faulty IC but the issue seems to be elsewhere. :(
Sorry to hear that didn't get it going yet, I'm pretty exhausted today but I'll check over the new voltages tomorrow. These things can take time :) it's a big circuit.
I don't think the melted cap will have harmed it, no.
Do you have an audio probe? http://diy-fever.com/misc/audio-probe/
If you probe IC1 Pin 7, you should hear your signal loud and compressed, Q7 collector it should be very muffled and IC11 pin 7, a square wave.
Thanks Scruffie.
Tyt and rest. I'm also having a stressful time at work, gets worse each year ;D. I replaced also C15 with a new component just to have all parts working...still no change in sound. I ll be in touch if you find any anomalies in the latest V measurements I sent you. No hurry, I will probably have no spare time to work on the pedal until next week. Appreciate your help. best regards, A
Hello Scruffie.
Build myself a probe and tried as you suggested...unfortunately none of the sounds were as you described...Both IC1/pin7 and Q/c emit a weak sound signal, on IC11/pin7 the signal is significantly stronger but linear and not wavy at all. :-[ ..frustration. Any other options/clues suggested by the Volt measurements I posted last time?
Thanks,
best regards,
Alex
I should have mentioned, you need the sensitivity control turned up or else there wont be any signal in those areas.
Also, just to be sure, you do get your input signal at IC1 pin 1, yes?
Ok, redone the experiment..I actually plays as you said loud+comp on IC1, muffed on Q7 and IC11 sq. waves of distorted signal. This means the pedal works? Or is there a step 2? :D
Well, only you can tell if the pedal is working and the octave is present now?
If not, that at least tells us that all the signal conditioning circuitry is working and narrows the issue down to the 4013 & Q4/8.
So if you audio probe pin 2 & 12 of IC13, do you get 1 & 2 octave down?
If yes, we know for some reason Q4 & 8 aren't passing it through to the output, if not, replace the 4013.
Hmmm...probed all 3 positions with the same result... very distorted hot lead like sound...cant hear difference in octave of any kind...probably 4013 duff too?
...that would be the 2nd faulty part in the kit so far :(
You can try re-flowing the solder joints on it again which may be all that's wrong, but they are a static sensitive part so having fried it is a possibility.
Thanks a lot for your help. I will try re-flow the component later and test again. In the worst cse I ll tryto find a substitute part.
Will stay in touch. thany again,
best regards,
A
Hi again.
I checked and reflew some joints on IC13 dis some probing and another round voltage measurements...
While probing I noticed no sound on pin 2 and 12, also on q4 and q8. Also theE on Q7 and IC11/p7 appear quiet this time... no muff, no sq. wave.
voltage measurements on Q4 and Q8 same as last time but consistant change on IC13 pins since last time (the component probably got busted while handling I suppose?).
1st measurements: p1 0.00 / p2 9.04 / p3 8.99 / p4 0.00 / p5 9.03 / p6 0.00 / p7 0.00 / p8 0.00 / p9 9.03 / p10 0.00 / p11 0.00 / p12 9.03 / p13 0.00 / p14 9.03
2nd measurement: p1 6.99 / p2 7.65 / p3 8.98 / p4 6.99 / p5 9.03 / p6 6.99 / p7 6.99 / p8 6.99 /p9 7.00 / p10 6.99 / p11 6.99 / p12 6.99 / p13 7.59 / p14 9.03
There is a 7v on all positions that had 0.00 before...joints seem all good now...probably a fried IC then?
:(
You must have muffled sound (which is actually a sine wave extracted from your input signal) on Q7 collector first, followed by square wave on IC11 pin 7 (follow the schematic) before you get anything on IC13, so you need to find out why that's disappeared again.
But also, your new IC13 measurements, on the second set, you have no ground on pins 4,6, 7, 8, 10... they should all read 0V. Your first set was closer.
Hello.
I managed to re-flew the joins on IC13, voltages are now the same as in the first measurement, must have been a bad joint somewhere.
I probed all the way from Q7 to IC11 and probably found the cause of the issue...I have the muff on Q7, the signal is fine past R82 and C12 as well as on pins 2 (3.5v) and 3 (3.5v) of IC11.
In the other side voltages on pin 5,6,7 of IC11 are p5 8.95 / p6 8.69 / p7 8.99 ...are such voltages adequate on these pins?...because there is no audible wave as before...just empty signal...does this tell me that probably the LM311N in bad? Reflew all joints on IC11 but no change. :o
LM311 aren't hugely sensitive and you said it worked before, although I suppose it is possible it died with overheating...
What happens to it if you a) remove IC13 and b) remove IC12?
Hi Scruffie me again.
I removed temporarily all the sensitive components and did a reflow on some suspicious pin joints of IC13 and IC11...Still no change in Subharm function.
I tried replacing both IC13 and the LM311 with new components from the local electronix shop. Done probing each component after IC12 ...just jacked in my pc with some easy acoustic guitar riffs, 15w amp and go...it resulted that from IC12 forward music could be heard on every component until the region of c30, c31, r85 and finally IC13...Could be a fried cap maybe?
Moving forward I also did the test you suggested...removing IC13 but probing on IC11/p7 no wave...the only audible thing is just a slight whistling noise that my 9v adapter makes. When I removed IC12 changes happened...no clean sound could be heard, just a distorted noise coming in sq. waves on IC13/ p2, p12 and IC/p7...does this give us any clues?
When plugging in my guitar the fuzz is more fuzz-like than the first testing a few weeks ago that sounded more overdrivish with no fuzziness. Bass switch works, tone, blend all works except for the subharm that is not present nor does change while turning the pot.
I'd appreciate any clues. I tried to explain in detail all the testing and results...frustrated. I think something must be wrong just before IC13..should I try to remove or. at least test the caps?
thank you, Alex
Okay, so you wont get octave or anything from IC13 without a square wave coming from IC11.
But, we've determined without IC12, you do get a square wave... does it change in pitch with playing?
IC11 is an oscillator that tracks the pitch of your guitar, IC12 'mutes' this so that it isn't constantly running (oscillating) and you get single notes.
So if without IC12 you are getting a square wave that tracks your input pitch, then the issue must now be around IC12.
Hmm..playing without the ic12 does not change the pitch. The effect souds like a vibrato. :-[
Where are you probing when you get the 'vibrato'?
By vibrato I assume you mean tremolo? As in a repeating on/off signal?
Pitch might have been the wrong word, does playing change the on/off time?
The trem effect occurs while playing guitar without the ic12...wasnt probing...just tried it plugged normally. On off time does not change by playing...like a tremolo effect all the time when the pedal engaged.
You need to be probing IC11 output (pin 7) but first be sure you definitely still have an input signal to it at pin 3 and make sure sensitivity is full CW while you are testing.
Hi Scruffie.
Spent a few hours during weekend doin some testing and probing...
I am clueless except for onbe thing...while probing around diode n16 I noticed that there is sound on the + pole but a static whistle on the opposite side...same whistl can be heard on IC11/p7 and IC12.
Could that be a faulty diode causing the issue? It is right before the IC12 or am I wrong?
ty,
Alex
My second guess would be a faulty 150p cap on C30 position...one pin has 8.99V and the other 0.00. burned???
Quote from: aleximan on April 11, 2022, 09:54:33 AM
My second guess would be a faulty 150p cap on C30 position...one pin has 8.99V and the other 0.00. burned???
One pin is the 311 output which is obviously giving 8.99V and one is the ground, so no, that's not faulty.
Audio probing is only really useful if you're tracing your input signal, for example on cathode of D16, when playing, you should get a fuzzy octave up version of your guitar signal.
Did you have input signal on pin 3 of IC11?
I suspect it's probably just a bad solder joint or two somewhere rather than faulty components... just a question of where!
Probing D16 cathode the speaker of my amp plays a fuzzy and bright octave effect...as you said.
Problem is the input signal on IC11/p3...signal voltage = 3.54v but the sound comes out in form of a perceptible static whistle (my 9V adapter emits this sound usually when attached to my other mooer pedal.) ...
and I agree it is probably just a cold joint somewhere before IC12...er else?...which part of the diagram comes prior IC12 and it is key? For example: The whistle is heard on both pins 6 and 7 of IC12..one louder, the other almost mute but still a whistle, no music...should I check the joints of components from D16 or other directions?...feel a bit lost. It has become such a tought maze for me to resolve...It is definitely not a project for greeners like me :D :D :D
Oh, okay, when you talked of a static whistle before I thought you were just talking about around D16.
So, if you probe C27, do you have a muffled representation of your input signal on both sides?
Assuming that is the case, the areas to focus on for bad joints, incorrect values etc. will be everything south of D16 anode, so R45-49, IC12 and IC11, R80-85 plus caps.
Is this your very first project then? While it doesn't involve the set up complication of a delay based effect, on sheer parts count alone, certainly a... brave choice :D
It may be wise after a couple more stabs at it to set it aside and come back to it once you've got a few more projects under your belt, even the experienced builders know when to take a break.
This is actually my 2nd build. I put together succesfulla a germanium fuzz face clone and I wanted to continue in fuzzy style but adding the octaves...the kit seemed perfect in terms of taste, now I realized a little less perfect in terms of my knowhow to put it together :D :D :D
Probed C27...I have the muffled sound on both pins..
Gave another try re-soldering the IC12 base and I found again the wave (whw IC12 removed), vhen installed music can be heard only on pin2 of IC11, the other have the same whistle as before.
...as you suggested..I will probably put it in a drawer, learn a few more things in electronics ant the maybe someday reopen itand succesfully fix it. Its frustrating at this time.
thanks for all the assistance. Will stay in touch ;)
best regards,
Alex
A fuzz face to this is less of a jump and more attempting to flap your arms and fly ;D
Oh, sorry, that's my fault, audio at IC11 pin 2 is right.
Well, I think you're close, but I can't think of what to suggest at the moment apart from methodically checking all your values and solder joints in the two areas. You've tried replacing the chips and while not impossible, passives such as diodes, caps and resistors being faulty is rare. Perhaps a week or two away will give you a fresh set of eyes.