Introducing myself and CE-2 debug cry for help!

[cathexis]

Hi everybody!

My name is Lars, I'm from Stockholm, Sweden. I've lurked on this forum for a year and a half
on a daily basis. I've built over sixty pedals since then, with no prior experience of
electronics whatsoever (I'm a psychologist). Everything I know about this I've learned from
you. I started out building from vero layouts by Torchy, Dragonfly, Marty, Slacker (loved the
EchoBase!!!) et al, then I started making my own vero layouts using Bancika's eminent
software. I've stuck to vero, since I have small children around and don't want to mess
around with the chemicals necessary for etching.
Vero has worked real well for me, and I've managed to build some rather big and complicated
circuits without much trouble. Among others I've built the following: Rebote 2.5, Small
Clone, Mu-Tron III, Meatball, Bassballs, Phase 90, Highway 89, BSIAB2, Big Muff, Vanishing
point and lots more - all sounding great.

All in all, I've had a great eighteen months on this forum, I have learned an immense lot
about the craft and the results have been overwhelming. Thank you!
I had planned to introduce myself to the forum as soon as I felt I could contribute
something, a nice vero layout maybe, but haven't really gotten around to it yet. So I'll
start with a call for help (maybe there's a nice vero layout in this after all...).

I spent christmas up north away from computers, and between meals I drew some layouts with
pen and paper. I'm still putting the finishing touches on a Neovibe vero, ant that's a big
one! I also did the CE-2 using the scematic at Tonepad, and as soon as I got back to
civilisation I started building - real eager since I loved the Heladito/Small Clone I did
last spring.

And I ran into trouble... I've had some lengthy debug sessions before, and can be pretty
stubborn. I have gotten all my prior builds to work eventually. Once I tore down a board
three times only to find a dead volume pot at the end of the week or so of tearing my hair
But this chorus has me super-stumped. The layout seems good to me (if a little large and
jumper-heavy), I've checked and checked, but I can't get my head around some of the voltages.

Can anyone help?

Pictures of my hand-drawn vero layout and the board can be seen here (hope I get this right):

[img=http://img222.imageshack.us/img222/2899/ce2veroboardlt7.jpg]

[img=http://img222.imageshack.us/img222/2972/ce2boardme1.jpg]

And here's the sad facts:

---------------------------------------------------------

1.What does it do, not do, and sound like?

Weak chorusing effect, hardly noticeable with speed and depth cranked, weird voltages on the MN3007 and MN3101, see below.
All controls seem to work as they should. No distortion on the output, hardly any clock noise.

2.Name of the circuit =

Boss CE-2 chorus, Corrrral Chorus

3.Source of the circuit (URL of schematic or project) =

http://www.tonepad.com/getFile.asp?id=101

I made my own veroboard layout, see:

[img=http://img222.imageshack.us/img222/2899/ce2veroboardlt7.jpg]

4.Any modifications to the circuit?

Vibrato Mod
Wet bass switching mod
Effect level mod
Chorus intensity cap switch mod
(as per the Tonepad project instructions)


5.Any parts substitutions?

TL062 substituted for the original TL022 (IC2), I also tried a TL072 with no noticeable difference.
11v zener diode instead of the RD11B.
(these subs have worked for many others on the forum)

6.Positive ground to negative ground conversion?

N/A

7. Voltages:

Battery= 9.3v

IC1 (4558)
1= 6.1v
2= 6.1v
3= 6.1v
4= 0v
5= 6.1v
6= 6.1v
7= 6.1v
8= 9.3v

IC2 (TL062)
1= VAR
2= 4.6v
3= VAR
4= 0V
5= 4.5v
6= 4.6v
7= VAR
8= 9.2v

IC3 (MN3007)
1= 9.0v
2= 13.7v    (!!!)
3= 5.3v
4= 0.6v
5= 0v
6= 13.3v    (!!!)
7= 4.7v     (?)
8= 4.7v     (?)

IC4 (MN3101)
1= 9.0v
2= 13v      (!!!)
3= 0v
4= 13v      (!!!)
5= 0.6v
6= 8.7v
7= 3.7v
8= 0.6v

Q1
C= 9.3v
B= 5.2v
E= 4.8v

Q2
C= 9.2v
B= 5.8v
E= 5.3v

Q3
C= 9.2v
B= 5.4v
E= 5.0v

Q4
C= 9.0v
B= VAR     (?)
E= VAR     (?)

Q5
C= 7.3v    (fluctuates a little)
B= 0.6v
E= 0v

Obiously something is very wrong here, but I cannot find it nor figure it out. Go ahead - make me feel stupid

Debugging performed: Went through the board several times, can't find any components in the
wrong places, no solder bridges. I reflowed every solder joint. Electrolytics and diodes have
the right orientation. I read through lots and lots of posts, learned a lot about the
circuit, but found no mention of those weird voltages. I even tried to lift the eigth pin of
the 3101 (bad batch theory) - no go. Stumped. Utterly and terribly stumped...

And finally - if you don't want to end up like this: BUY YOUR PCB:S FROM TONEPAD! They're
great, and vero can be hazardous to your mental health

Thanks for your time,

LARS

[miqbal]

Have u try turning the trimpot on any direction? Just in case....

[cathexis]

Thanks, yeah I've turned the trimpot to where i get the most prominent chorus effect - not that it is very prominent at all. 

All the voltages seem pretty consistent with those posted earlier by André Schaap, here:

http://www.diystompboxes.com/smfforum/index.php?topic=56283.20 reply # 30

apart from those really high ones on pin 2 + 6 on the 3007 and pin 2 + 4 on the 3101. 13 volts?!? How is that possible?

Still stumped,

LARS

[johngreene]

Thanks, yeah I've turned the trimpot to where i get the most prominent chorus effect - not that it is very prominent at all. 

All the voltages seem pretty consistent with those posted earlier by André Schaap, here:

http://www.diystompboxes.com/smfforum/index.php?topic=56283.20 reply # 30

apart from those really high ones on pin 2 + 6 on the 3007 and pin 2 + 4 on the 3101. 13 volts?!? How is that possible?

Still stumped,

LARS

What do you get with the vibrato switch enabled? (eliminates the dry, to check the audio level of the wet).

[cathexis]

What do you get with the vibrato switch enabled? (eliminates the dry, to check the audio level of the wet).

I get a nice vibrato, but just as with the chorus effect it's really, really subtle. A slight volume loss without the dry signal added, not much at all.
If I put a large cap in parallel with C22 (like maybe a 2 uF NP) the modulation of the wet signal gets to be more noticeable, but still by far not as deep as to be expected.

[johngreene]

What do you get with the vibrato switch enabled? (eliminates the dry, to check the audio level of the wet).

I get a nice vibrato, but just as with the chorus effect it's really, really subtle. A slight volume loss without the dry signal added, not much at all.
If I put a large cap in parallel with C22 (like maybe a 2 uF NP) the modulation of the wet signal gets to be more noticeable, but still by far not as deep as to be expected.

It sounds like the modulation of the clock is not working very well. So the problem is more than likely in the area of IC2, Q4 and IC4. Since you are getting some kind of vibrato, the MN3101 appears to be running, it just isn't moving much. C22 and the switch are located pretty far from IC4 which could be a problem. I would remove the jumpers going to the switch and tack C22 to the strips closest to IC4 until you get the circuit working.
I just noticed that the connection between pin 8 of IC4 and pin 4 of IC3 is not at a good voltage. I would try lifting Pin 8 and measuring it to see if it is sitting at around 8.7 volts. If not, your MN3101 may be damaged. If it is at 8.7 volts with the pin disconnected, then you either have a short on the board or a problem (bad?) 3007.

--john

[cathexis]

I just noticed that the connection between pin 8 of IC4 and pin 4 of IC3 is not at a good voltage. I would try lifting Pin 8 and measuring it to see if it is sitting at around 8.7 volts. If not, your MN3101 may be damaged. If it is at 8.7 volts with the pin disconnected, then you either have a short on the board or a problem (bad?) 3007.
--john

Thank you for your suggestions, I'll try them as soon as I get home from work. Do you mean I should lift pin 8 of the MN3101?

[miqbal]

I just noticed that the connection between pin 8 of IC4 and pin 4 of IC3 is not at a good voltage.

I thought the voltage on the pin 8/IC 4, i.e. pin 4/IC3 is pretty close to Andre's  (cathexis's mentioned before).

This is from Andre

[johngreene]

I don't know anything about Andre's measurements but according to the datasheet for the MN3101 and MN3007:

http://www.synthdiy.com/show/file/?id=845

Pin 8 on the MN3101 should be 14/15 of the supply voltage. This provides bias to the gates of FETs inside the MN3007. Will it still work with the voltages measured? I don't know for sure, but the MN3101/MN3007 pairs I've measured have always been with a higher voltage on the pin 8 - pin 4 connection.

--john

[cathexis]

Thanks for taking the time to try to help me through this!

I tried lifting pin 8 of the MN3101 (IC4). It still reads 0.6v when I measure the pin. Pin 4 on the MN3007 (IC3) now slowly drops from about the same voltage to about 0.2v. I took out the MN3007 and tried it in my Small Clone, and that pedal sounds like it always has, so it seems the 3007 is OK.
I should probably desolder my IC sockets and check for shorts or mistakes there...

[johngreene]

Thanks for taking the time to try to help me through this!

I tried lifting pin 8 of the MN3101 (IC4). It still reads 0.6v when I measure the pin. Pin 4 on the MN3007 (IC3) now slowly drops from about the same voltage to about 0.2v. I took out the MN3007 and tried it in my Small Clone, and that pedal sounds like it always has, so it seems the 3007 is OK.
I should probably desolder my IC sockets and check for shorts or mistakes there...

You could also connect Pin 4 of the MN3007 to the supply (9V) through a diode to get approximately the same thing. If the MN3101 is generating clock then the MN3007 should be happy and all should work.

Did you measure pin 4 of the MN3007 in your small clone?

--john

[cathexis]

Found it!

Turns out it was one of the simplest errors - I miswired the switch for the chorus intensity switch. C22 was completely out of circuit... (you can see this on the pic of the board posted above - the layout is right, though). Fixed it, and now I got a working chorus! When I measure voltages now I get this:

Battery= 9.1v

IC1 (4558)
1= 6.1v
2= 6.1v
3= 6.1v
4= 0v
5= 6.1v
6= 6.1v
7= 6.1v
8= 9.0v

IC2 (TL062)
1= VAR
2= 4.5v
3= VAR
4= 0V
5= 4.5v
6= 4.5v
7= VAR
8= 9.0v

IC3 (MN3007)
1= 8.9v
2= 4.7v   
3= 5.3v
4= 0.6v
5= 0v
6= 4.7v   
7= 5.2v     
8= 5.2v     

IC4 (MN3101)
1= 8.9v
2= 4.7v     
3= 0v
4= 4.7v     
5= 0.6v
6= 5.5v   (?)
7= 4.4v   (?)
8= 0.6v

Q1
C= 9.3v
B= 5.3v
E= 4.9v

Q2
C= 9.0v
B= 5.8v
E= 5.3v

Q3
C= 9.0v
B= 5.4v
E= 5.0v

Q4
C= 9.0v
B= VAR     (?)
E= VAR     (?)

Q5
C= 7.8v   
B= 0.6v
E= 0v

As you can see the voltages now mostly corresponds to those posted by Andre (quoted above), apart from pin 6+7 of IC4 MN3101, and the variance of B+E of Q4. I'll see if I can iron these out before we can consider this vero layout verified as working. It sure sounds good already though. I A/B:d it with the built-in chorus of my Roland Cube and analog sure has the advantage...

Thanks for all the help this far! Suggestions on the remaining errant voltages would be very welcome, of course...

Unstumped, swirling,

LARS