LectricFx Downtown - SubHarm pot not working

[aleximan]

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. 

Aleks

[aleximan]

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. 

Aleks

[Scruffie]

Ebay might not be the best place to find one...

Try asking in the parts jar sub-forum here.

[aleximan]

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.
Thanks for your feedback.

br, A

[Scruffie]

Looks better, give it a try.

[aleximan]

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:



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.

[Scruffie]

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.

[aleximan]

Thanks Scruffie.
Tyt and rest. I'm also having a stressful time at work, gets worse each year . 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

[aleximan]

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

[Scruffie]

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?

[aleximan]

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?   

[Scruffie]

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.

[aleximan]

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

[Scruffie]

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.

[aleximan]

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