Help with CE2 debugging

[vex]

First off this place has been an excellent resource for me to lurk and search through.  I've done five successful builds and this one.    I've been looking at it on and off since May and decided it's time to ask for some help.

http://www.tonepad.com/project.asp?id=53

I'm using the board from Tonepad, signal is passing through but I'm getting no chorus effect.  I do hear a faint ticking but I'm not concerned with that.

This is a straight build with no modifications.

Any advice on where to start looking is appreciated.

Here is what my voltages look like.

IC1 4558
1-   6.5
2-   6.5
3-   6.5
4-   0
5-   6.5
6-   6.5
7-   6.5
8-   8.5

IC2 TL022
1-   Var
2-   4.2
3-   Var
4-   0v
5-   4.2
6-   4.2
7-   Var
8-   8.4

IC3 MN3007
1-   6.8
2-   1
3-   5.6
4-   .1
5-   0
6-   .1
7-   2.7
8-   2.7

IC4 MN3101
1-   6.8
2-   .1
3-   0
4-   1
5-   .6
6-   5.8
7-   2.5
8-   .1

Q1 5088
C- 8.2
B- 5.5
E- 5.1

Q2 5088
C-8.2
B- 6
E- 5.5

Q3 5088
C- 8.2
B- 5.6
E- 5.2

Q4 5088
C- 6.7
B- Var
E- Var

Q5 5088
C- 5.3
B- .5
E- 0

[Andre]

The voltages on pin1 of both the MN3007 and the MN3101 are too low.
They should be only little less than the voltage on pin 8 of IC1.
Please check the value of R52 (33 Ohm).

For reference here are the voltages of my Tonepad CE-2:


André

[vex]

Thanks Andre!  I had checked R52 earlier and it read 33 ohm but my wife convinced me I had to pull it to measure it properly and it still says 33 ohm.

I'm not sure if any of this is significant and I used my power adapter here so the voltages here are higher but here is what I did find.

Voltage before the resistor with the power adapter is 9.45 and power after is 7.7 (same as pin 1 of IC4) and still too low.

If I pull IC4 voltage at the resistor and on the socket at pin 1 is 9.33 which sounds more like it.

I tried a spare MN3101 in IC4 and voltage at pin 1 and the resistor was 4.4 and it got a little warm.

Is it possible I have two bad 3101's?

John

[Andre]

Is it possible I have two bad 3101's?

Not very likely.

What happens if you pull out the MN3007 and leave the MN3101 in?
Either pin2 or pin4 of the MN3101 should be high, but now there both low, which could mean they are shorted by the MN3007.

André

[vex]

Thanks again for taking the time with this Andre.

If I remove the 3007 pin 2 on the 3101 changes from .19 to .79 and pin 4 from 1.04 to 1.18 so not a huge jump.   If I replace the 3007 with a spare then voltages on pin 2 and 4 of the 3101 are .13 and .98 respectively and pin remains at 7.7

jc

[Andre]

John,

Possibly there's something wrong with C9.
It could be defective or soldered in the wrong way around.

André

[vex]

I ended up order a new MN3101 from a different source and it is now working.  It tics pretty bad but I know there is lots of info here on fixing this.

Thanks again for your help.

[DimebuGG]

It tics pretty bad but I know there is lots of info here on fixing this.

that's strange. Even using a TL072 in the LFO doesn't makes ticking.

Oh btw, did you adjust the trimpot?

[vex]

that's strange. Even using a TL072 in the LFO doesn't makes ticking.

Oh btw, did you adjust the trimpot?

I did mess with the trimpot and tried both a TL022 and TL072.  I'm going to try some insulated wire I just haven't picked any up yet.  I thought the ticking was a fairly common problem.

[beatnik]

i don't want to start a new topic, since the problem is the same...

...ce-2 to be debugged!!

i post my voltages, the most strange thing is that i have Vref= 1,6 V and not 4,5 V.... what could be?

first i founded that D2 was reverse, but anyway i have no sound coming to the output.

with the audio probe i only have weak signal on IC1 and clicking on the 022.

Please help me to find the problem

IC1 4558
1-   1.4
2-   1.35
3-   0.95
4-   0
5-   0.96
6-   1.36
7-   1.40
8-   9.30

IC2 TL022
1-   Var
2-   4.6
3-   Var
4-   0
5-   0
6-   4.3
7-   Var
8-   9.3

IC3 MN3007
1-   9.20
2-   4.75
3-   0.41
4-   0.62
5-   0
6-   4.69
7-   3.65
8-   3.67

IC4 MN3101
1-   9.20
2-   4.70
3-   0
4-   1.70
5-   0.35
6-   8.03
7-   3.00
8-   0.62

Q1 5088
C- 9.30
B- 0.63
E- 0.39

Q2 5088
C-9.3
B- 0.83
E- 0.42

Q3 5088
C- 9.3
B- 0.69
E- 9.30

Q4 5088
C- 9.20
B- Var
E- Var

Q5 5088
C- 7.5
B- 0.42
E- 0

[Andre]

beatnik, what happens if you turn VR3?
VR3 sets Vref as well as the BBD bias voltage.
First set vr3 so Vref is 4.5V.
Now you should hear your clean signal and maybe some chorus.
If not, slowly turn VR3 so that Vref goes up until you hear chorus.
Now find the two positions of VR3 where the chorus signal stops en set VR3 right in between those positions.
Your Vref will probably be a bit higher than 4.5V, but that's no problem.
My CE-2's Vref setting is 6.1V.

If Vref does not change when you turn VR3, check the area around VR3, R27, R28.

[beatnik]

andre you had surgery precision!!!!

i had wrong values for both R27 and R28... i changed for the right ones and volia the chorus is here.

the only problem is the lfo ticking, wich is very loud when i use the chorus on amp distortion.

you know any way to fix it? maybe shielded wire for the input and the output?

many thanks for your help and greetings from italia

[anchovie]

I read that the best way to avoid ticking was to use an op-amp with a low current draw for the LFO. I'd originally tested the board with a TL072 which gave audible ticking, an LF353 made it slightly quieter but it was still there. Got hold of some TLC27L2 cheap of Ebay and the LFO is now silent - they only draw 20 microamps!

[beatnik]

thanks for the tip james... i have some different ics so i will try them and compare

i also notice that if i let the in and out cable away from the lfo section the tick disappears

so for sure when i'll box it up i'll keep them away