more Corral Chorus/CE-2 debug

[ncudahy]

Hi! this is my first post to this forum ( I think ). I'm a musician living in Brooklyn, NY. Just got back into building stuff after a long time off. Made a lot of the the Craig Anderton stuff in the 80's....

Anyway my issue with this pedal is that the signal makes it to the output but with only a trace amount of chorus effect. I had everything in nice tables that i can't seem to get to work here, but anyway, here are my voltages:

SUPPLY VOLTAGE: 9.05

Q1 E5.38 B4.22 C9.03
Q2 E5.9 B5.76 C9.03
Q3 5.51 B4.61 C9.03
Q4 E3.1-3.9 B3.0-3.9 C8.9 seems to be varying according to LFO
Q5 E0  B0.4 C7.1

4558
1: 6.72   8: 9.03
2: 6.72   7:6.72
3:6.63    6:6.72
4: 0       5:6.7

TL022
1: VAR 3.XX-5.XX    8:9.03
2:VAR 4.4-4.42        7:VAR
3: VAR 3.6-5.1         6:4.03
4:  0                     5:VAR 4.40-4.42


MN3007
1:8.9                                 8: 5.86-5.88
2:4.66-4.68 1Usec sq wave  7:5.86-5.88
3:3.6-5.1                            6:4.03
4:0.6                                    5: 0


MN3101
1;  8.9           8:0.6
2:4.59-4.60    7:2.88-2.93
3:0               6:7.78-7.85
4:4.66-4.67    5:0.27-0.30


I replaced the 3007 and 3101 with extras that i ordered from the same supplier. with no change.  Everything looks healthy to me compared to voltages of a functioning ce-2 that someone posted. I did read a post though, that said that the LFO voltage swing should be from almost 0 to 9 volts. Not the case with mine. I get around 3.5-5.5V. i replaced the TL022 with a TL072 with no change. The trim pot is working. I included those minor variations in voltage because they might mean something to someone more knowlegeable than me. they appear to just be following the LFO.

I put a cap substitution box in parallel with C22 to see if that would increase depth. What I got was oscillation added to the signal which was modulated by the LFO rate and varied in pitch as capacitance increased.  I also tried to vary the resistance of R13 by putting a resistor sub box in || but there was little or no audible result. 

So right now the only thing i can think to try is to increase the output swing on the LFO, or possibly beef up the wet signal coming into IC1b. Not sure how to do this so any help there would be appreciated. Thanks for taking the time to read this and thanks in advance for anyone kind enough to take this on!

ok i better post this now before i get signed out haha!


   

[scuzzphut]

I've just finished my CE-2 and had a SWINE of a debug with it.

Here are some of the things I found :

• One of the problems I had was that all of my transistors were back-to-front.  I followed the orientation of the layout , but later discovered that the 2N5088s I had bought were the opposite pinout.
• One leg of the trimpot for the bias voltage had a cold joint.  My bias voltage was swinging around 8v where it should be 4.5ish.
• An issue with no oscillation - a static voltage at pin 7 of IC4 and pin 3 of IC2.  THis was traced to a solder bridge at C19 to the 9V rail.
• An issue with the 9V supply to IC3 and IC4 dropping to 8V when the ICs were inserted - a quick scrape around their pins sorted that out.

It's all documented in this thread - which also has more wisdom relating to the Corral. Give it a quick scan !!

http://www.diystompboxes.com/smfforum/index.php?topic=99887.msg876882#msg876882

[ncudahy]

Thanks man, glad you got it going! that thing with the 5088's is bizarre! will check out that link.

[scuzzphut]

I meant to wish you good luck and to encourage you to keep going.

I got incredibly frustrated with my build, but now that it's working I am really happy I persevered. This chorus is really thick and lush.

I sold my Boss CE-5 once I'd finished my Corrall. I knew I'd never use it again.  (true story - *clink*)

[ncudahy]

Hehe! Thanks! Yeah it can be really frustrating at the same time you learn A LOT when this happens. and it can be fun to check out all the different stages of the circuit on the scope. still I'm ready for it to work now haha! checked out that thread and the trick of lifting R21 was a good one. So the effect signal sounds the way it is supposed to but the level is a fifth of what it should be when i compare the input waveform with just the effect waveform on the scope. but my signal tracer tells me the output from the 3007 is about the same level as the input at least to my ear anyway. more difficult to compare those on the scope.

anyway it seems like maybe something in the path from the output of the 3007 is overly attenuating the signal. checked the resistor values everything is what it's supposed to be. but one resistor looked kinda lumpy and funky so i changed it...and lifted the pads while doing so kludged everything back together and it's still working in the same dysfunctional manner as before.

could it be a cap?

ok, well thanks for the encouragement and sharing your story. Got a gig in a while so I guess I gotta switch gears now.