Copy Boss Chorus CE-2 (Corrrral Chorus) not modulate

[pinio]

Hi

I build effect from tonepad project Corrrrral Chorus. This is Boss Chorus Ensemble 2 with omitted buffered bypass.
http://tonepad.com/project.asp?id=53
http://tonepad.com/getFile.asp?id=101 pdf

Signal going through system. On the output is pretty clear signal. Effect not modulate...

I took out the IC responsible for the LFO, but no change. I changed to another - the same. Witch or without IC2 (TL022 or MC1458) and IC4 (MN3101), signal still the same.

Q4 and Q5 are 2N5088. In original Boss are 2SC945-P.

In what places to measure voltage, where to find the problem?

Original CE-2
http://www.hobby-hour.com/electronics/s/boss-ce2-chorus-schematic.php

PS. Sorry for my English

[geertjacobs]

First check out the sticky topic "what to do if it doesn't work".
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Also check out this topic:
http://www.diystompboxes.com/smfforum/index.php?topic=89419.0

[Seljer]

Are you sure its the LFO thats not LFOing and not the delay chips thats not delaying? check with an audio probe on the output of the BBD chip and around what is Q3 in that schematic

[pinio]

OK. I read about cross reference for 2SC945-P. I gave a 2N3904. They seem to be closest to the original. 2N5088 have larger HFE.
Measured the voltage:
+9V - 8,07V
before R52 - 8,03V

Vb - 4,13V (2 leg trimpot)
1 leg trimpot - 2,06V
3 leg trimpot - 5,94V

IC1:
1 - 0
2 - 4,08
3 - 4,08
4 - 0
5 - 4,08
6 - 4,08
7 - 4,08
8 - 8,07

IC2:
1 - 7,63
2 - 8,03
3 - 4,90
4 - 0
5 - 8,01
6 - 1,50
7 - 7,30
8 - 8,01

IC3:
1 - 7,92
2 - 4,03
3 - 3,44
4 - 0,53
5 - 0
6 - 4,01
7 - 3,33
8 - 3,33

IC4:
1 - 7,92
2 - 4,01
3 - 0
4 - 4,04
5 - 3,23
6 - 4,44
7 - 3,20
8 - 0,53

Q2:
E - 3,49
B - 4,14
C - 7,70

Q4:
E - 1,67
B - 2,25
C - 7,93

Q5:
E - 0
B - 0,57
C - 6,11

D1 :
3,25 - 0,79

D2:
6,08 - 0


What are the measurements I have done to diagnose the lack of waves in this Chorus?

[hannibal827]

Are you sure its the LFO thats not LFOing and not the delay chips thats not delaying? check with an audio probe on the output of the BBD chip and around what is Q3 in that schematic

I agree that this is the most likely issue.  Have you tried adjusting the trimpot [VR3] to get a higher voltage on pin 3 of the delay chip [IC3]?  Without a high enough voltage there the chip won't work.

[pinio]

Both wet and dry analog signals are ok and present.

On legs 2 and 4 MN3101I hear buzz.

On legs 3 and 4 MN3007 I hear sound (from input), on 7/8 little distorted, but on E Q3 it's ok.

Yes, VR3 I adjusting to higher voltage.

[hannibal827]

Pins 2 and 5 of IC2 should have a lower voltage reading.  You're getting about 8 volts there when you should be getting about 4 [or half of your supply voltage].  Check R33 and R34--those are your voltage dividing resistors.  Both should be 10k; R33 should have V+ on one lead and half of that on the other; R34 should have half of V+ on one end [the junction with R33] and 0v on the other.

[pinio]

Both R33 and R34 are 10k, but voltage on junction resistors is not half V+.... maybe should give something like R27-VR3-R28 and adjust 1/2 V+?

[Seljer]

There are two seperate sources of V+/2 on this circuit, one is used by the opamp that generates to modulation waveform, the other one with the trimpot (Vb) is for the audio part with the delay chip and from the voltage measurements you gave and the behavior of the circuit, that one seems to be operating normally.

The trace under R33/R34/C20 is awfully close to the +9V trace, check to see if you have a solder bridge there. Or if the the grounded end of R34 has a cold solder joint.

[pinio]

Anyway, I add trimpot parallel with R33/R34 and adjust correct voltage. When I put my fingers to the input and legs potentiometers (Rate, Depth) I hear a knock at the output of a frequency depending on the position of the potentiometer Rate. About few Hz.
Changed the MN-s, with no effect. Have I got the defective chips?

[Joseeduardosn]

Move the trimmer 'cause i had same problem. I moved trim and effect worked.