EHX Small Clone...but no chorus

Started by azrael, November 23, 2012, 03:11:02 AM

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azrael

Okay, I got an EHX Small Clone in a trade and I've been messing with it lately for fun.
Replaced the caps with WIMA box caps and whatnot, replaced the electros for nichicon, replace all the crappy EHX wiring.
One significant difference is that I lost the CD4047, and didn't have another one on hand. So I used a HEF4047, which I think should be just fine.

So what's the issue? No chorus! signal comes through, and I attached the LED to the LFO, so I can see the rate...so the LFO is working, I believe. I get signal at pins 7 and 8 of the MN3007, after adjusting the trimpot, but it's not chorused.

wtf! Is the BBD dead? Or is the HEF4047 not good for this circuit?
Here are my voltages. ish. I thought the bolded one was kinda odd.

Here are my voltages:
Q1 2N5087:
E = 4.9
B = 4.3
C = 0

Q2 2N5088:
E = 3.3
B = 4.4
C = 8.8

Q3 2N5088:
E = 8.2
B = 8.8
C = 8.8

4558:
1 = 4.4
2 = 4.4
3 = 4.35
4 = 0
5 = 4.35
6 = 4.3
7 = 8.5
8 = 8.6

LM358:
1 = 1.4-2.1 (changes between)
2 = 3.95
3 = 3.9
4 = 0
5 = 1.7-2.6 (changes between)
6 = 2.1
7 = 1.6-6.1 (changes between)
8 = 8.6

MN3007:
1 = 8.0
2 = 3.9
3 = 5.5
4 = 0
5 = 0
6 = 3.6
7 = 5.2
8 = 5.2

CD4047:
1 = 7.8
2 = 0.1
3 = 7.0
4 = 8.0
5 = 8.0
6 = 8.0
7 = 0
8 = 0
9 = 0
10 = 3.7
11 = 3.7
12 = 0
13 = 7.8
14 = 8.0


Keeb

Is this an original or a DIY-pedal?

I think you're right with pin 7 on the 4558 being off.
By looking at the schematic (tonepad.com version) pin 7 is connectod to pin 1 and 6 and not you really shouldn't get a higher reading on pin 7 compared to pin 6.
Check around that area and audio probe the circuit.

azrael

Original.

I don't know why it would be off, I haven't touched anything with that part of the circuit.
But that shouldn't affect the chorused signal?

pinkjimiphoton

changing the caps probably changed the bias point of the bbd slightly. i'm not familiar with this pedal (other than owning one years ago) but if it's anything like a clone THEORY, there's a relatively small window on the trimmer that sets the biasing for the bbd.
try turning the trimmer slightly... if the bbd is good, at some point you will hear it kick in. when (if) you get to that point, play with it, find out the min-max range where it works, and adjust for least distortion and you should be good to go.
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azrael

I adjusted it to where there's a signal coming through, found the min-max range, but haven't fined tuned it really.

Scruffie

You may have better luck biasing by killing the dry signal by lifting the 22k mixing resistor (same thing you'd do to perform the vibrato mod) so signal is only going through the BBD. You'll only hear the wet signal with the BBD properly biased.

That high voltage on pin 7 of the 4558 is not good... you should find out what's going on there, make sure you haven't got a hair joint between 7 & 8.

Your clock looks okay, has reasonable voltages.