Small Clone (fp layout) not chorusing..going crazy...

[itpowerse]

Hi,

I have been trying to debug my small clone for several months now. The small clone passes the signal, both clean and chorused but the chorused version is not chorusing ! The strange part is that I do get a chorus effect if I twist the 10k depth pot.

Bias is working, audio probe do pickup a signal in the "chorused" line which is obvious since I do get a chorus effect when manually tweaking the pot. This made me question if the 4047 and LM348 where working correctly so I order new ones....no change.

Please if anybody can help me here I would be eternally grateful. Please note that I have successfully built about 7 stompboxes without issues and I have verified the soldering and components...but as always you can miss something.

Anyway, here is my voltages:

MN3007
1 8,91
2 4,43
3 5,53
4 0
5 0
6 4,43
7 5,31
8 5,31

CD404
1 8,21
2 0
3 6,75
4 8,28
5 8,28
6 8,28
7 0
8 0
9 0
10 4,13
11 4,13
12 0
13 8,21
14 8,21

LM358
1 2,24
2 4,06
3 4,02
4 0
5 2,24
6 2,23
7 4,02
8 8,9

Q1
E 4,76
B 4,12
C 0

Q2
E 4,9
B 5,46
C 8,9

Q3
E 8,3
B 8,9
C 8,9

If anybody can give some guidance where to troubleshoot pleeease reply.

Thanks for a truly great forum!

Cheers from Sweden.
itpowerse

[Fp-www.Tonepad.com]

It is possible that you wired the depth pot wrong, I suggest you try wiring the regular spst depth switch and see if you get chorusing on both positions. Also, check the trimpot, most of the times it just sits close to the middle.

Fp

[snykanen]

So it's chorused but not swirling? I had the same problem, then I noticed the battery was only giving ~6V so the LFO wasn't working or something. Don't know if it's any help but try to change the battery.

[itpowerse]

OK

I know I doublechecked the depth pot (and changed to a new one) but I will try and replace with the switch.
The power is coming from a regulated supply which is driving a ts-808, phaser90 etc. without any problem so I don't think the power(battery) is wrong here.

I will let you know if it works.

Thanks,
Johan

[itpowerse]

Hi guys,

Soldered in the switch together with the resistors and still same issue. What I start to wonder is if the MN3007 is faulty although I can manually produce some chorusing with the (now removed) depth pot.
The range pot makes NO difference what so ever.

Maybe time to rip it all up and start over...

/itpowerse

[Fp-www.Tonepad.com]

Don't rip it, fix it!

What you describe is a not working LFO situation. You should be able to identify the components around the LFO and measure voltages on that IC.

Fp

[itpowerse]

Hi fp,

Thanks for you reply. Yes, I agree and I figure that the LM358 LFO filter part is not working. I will remove the capacitors and reistors since I have changed to a new LM358P and still the same issue.

Again, thanks for the feedback

itpowerse

[itpowerse]

Hi,

Did a new walk around the LFO section and measured all components and there it was. It turns out my bag of 120k resistors really contained 120 ohm ones !!! So in the feedback section of the LM358 there was a 120 ohm instead of a 120k resistor.

The chorus is working great now and no manual twisting necessary :-)

Like someone said "The person who makes no mistakes, makes nothing at all!"

Cheers,
Johan

[Fp-www.Tonepad.com]

Congratulations!

So, the 120ohm resistors were marked as 120k... that's a pretty bad error, but I've heard it happen before.

[itpowerse]

Fp,

Well, I had marked the bag wrong :-)

itpowerse

[Fp-www.Tonepad.com]

That's why reading resistor labels is important!

brown red black yellow=120k (unless your resistors are coded in 5 bands instead of 4)

Fp

[R.G.]

I won't even tell you how many times I've mistaken a 4.7K for a 47K and vice versa.