Debug: Tonepad Chorus

[OW]

Hi,

I'm trying to get a Toned Chorus pedal working - it was built via a DIY PCB.

Currently, when switched on sound passes through the pedal, however there is no chorus effect on the signal.

I've measured various points on the PCB and get the following values:

CD4047

1: 6.80
2: 1.10
3: 5.11
4: 7.97
5: 7.97
6: 7.96
7: 0
8: 0
9: 0
10: 0
11: 3.77
12: 0
13: 6.97
14: 7.97

MN3007

1: 7.97
2: 3.76
3: 3.39
4: 0
5: 0
6: 3.55
7: 7.88
8: 7.88

LM358

1: 1.66
2: 3.92
3: 0
4: 0
5: 2.15
6: 2.13
7: 3.81 - 4.01
8: 8.68

4558

1: 4.35
2: 4.35
3: 4.24
4: 0
5: 4.33
6: 4.34
7: 4.31
8: 8.68

D1

A: 3.41
K: 2.85

D2

A: 1.13
K: 5.11

Q1

C: 0
B: 2.24
E: 2.83

Q2

C: 8.68
B: 7.68
E: 7.11

Q3

C: 7.77 - 7.96
B: 8.60
E: 8.68

Does anyone have any ideas as to what's going wrong?

Here's a link to the project: http://www.tonepad.com/getFile.asp?id=97

Many thanks in advance!

[Govmnt_Lacky]

From the looks of your voltage reading AND looking over the Heladito board layout and schematic:

I believe your most likely culprit are shorted traces. Look here:

Between the LM358 Pins 3 & 4
Between the CD4047 Pins 9 & 10
Between the MN3007 Pins 5 & 6

Look for solder bridges and/or shorted traces in those areas.

Good Luck 

** Edited to change Pins on MN3007 **

[OW]

Thanks for the response!

I just checked around those pins but couldn't seem to find a short. I also cleaned up soldering around there and still nothing.

There is quite a volume drop when the pedal is engaged with the clean signal coming through

[Govmnt_Lacky]

Thanks for the response!

I just checked around those pins but couldn't seem to find a short. I also cleaned up soldering around there and still nothing.

There is quite a volume drop when the pedal is engaged with the clean signal coming through

** EDITED to change Pins on MN3007 in post above **

Did you remove those 3 ICs and measure resistance between the 2 socket pins of each IC? If no, then you should do that

If yes, then you may have a couple bad ICs 

For reference, MN3007 Pin 6 is directly connected to CD4047 Pin 10. In your readings, you say you are getting 3.55V on MN3007 Pin 6 but, 0V on CD4047 Pin 10. They should have the same voltage.

[OW]

Thanks!

I replaced the LM358 with a couple new ones I had and no change.

Apologies, I do actually have ~3.55 on pin 10 of CD4047.

I've checked solder bridges between the pins you specified and cleaned them up.

Perhaps it's a bad 3007?

As for measuring the resistance between the two socket pins, should I remove all ICs at the same time and measure between pins 1 and 2, 2 and 3, 3 and 4 etc of each socket? What kind of resistance would I be looking for?

Many thanks!

[Govmnt_Lacky]

I replaced the LM358 with a couple new ones I had and no change.

You need to remove ALL of the ICs from their sockets first.

For this, measure resistance (or do a continuity check) between the LM358 socket pins 3 & 4. It should read open or a large resistance.

Also, make sure there is no bridge (to GND) between the 68K and 82K resistors just above Q1. That could also cause the LM358 Pin 3 to show 0V.

Apologies, I do actually have ~3.55 on pin 10 of CD4047.

I've checked solder bridges between the pins you specified and cleaned them up.

Perhaps it's a bad 3007?

If CD4047 Pin 10 is good, then it could be the 0V you are seeing on the LM358 Pin 3. Do the above procedure and see what you get. If there is no problem with the LM358 socket and you are still not getting anything, you may want to look into adjusting the trimmer a bit more OR it could be the MN3007.

Good Luck 

[duck_arse]

please be posting photos of what you have built, component and solder sides, and all off board wirings, and let us have a look. and welcome to the forum.

[OW]

Managed to get pin 3 of LM358 reading 3.8 V.

Did a full sweep of the trimpot in both directions with signal running through and got no chorus.

Pins 7 and 8 or the 3007 look quite high? Should they be reading at around 8 V?

Resistances are really high, or open across pins when ICs are removed.

I've attached some photos - let me know if you need anything else, and thanks for all the help so far

[GGBB]

Resistances are really high, or open across pins when ICs are removed.

Please qualify this statement - it's important that you be specific - your words are our eyes. MN3007 and CD4047 should have connected pins:

[OW]

I can measure the resistance across all pins and post them if that's useful?

If not are there any specific pins I should measure the resistance of?

[antonis]

It should be better to measure the resistance between each pin and GND..