EHX Octave Multiplexer debug

[ozzy]

Hi all,

EHX Octave Multiplexer (the vintage version without boost)
http://tagboardeffects.blogspot.cz/2016/09/electro-harmonix-octave-multiplexer.html

Only hum comes out (sounding same like when touching an unplugged input jack). Any help will be much appreciated!






JFET 5459
D - 4.3
S - 4.3
G - 4.6

LM324 (upper one)
1 - 4.3
2 - 4.3
3 - 3.8
4 - 9.3
5 - 3.8
6 - 8.6
7 - 0.6
8 - 4.3
9 - 4.3
10 - 3.8
11 - 0
12 - 4
13 - 4.3
14 - 0.6

LM324 (one next to 4013)
1 - 8
2 - 0.9
3 - 0.9
4 - 9.3
5 - 0.9
6 - 0.9
7 - 0
8 - 0
9 - 0.9
10 - 0
11 - 0
12 - 0.9
13 - 8
14 - 0

4013
1 - 9.3
2 - 0
3 - 0
4 - 0
5 - 0
6 - 0
7 - 0
8 - 0
9 - 9.3
10 - 0
11 - 0
12 - 9.3
13 - 0
14 - 9.3

[Emil]

Hi!

I had a quick look and noticed a few things on the board. See the attached image.

1. Circled diodes needs to be turned the other way around.

2. That 100uf and 10k seems to be in the wrong place.

3. The resistors to the J-fet seems wrongly placed.

Also, if the diagram shows your off-board wiring then your input isn't grounded. Add a ground wire to the input sleeve. This would perhaps explain the humming.

[ozzy]

Hi emilpaulsrud!

Many thanks for your input. It looks like the layout on the project page has been changed. So it doesnt match with the original one I used :-(

The input sleeve is grounded through the enclosure so this shouldn't be an issue.

But thanks for your help anyway! I will start over and recheck everything again.

ozzy

[Alex]

Hi Ozzy.
Double check it against the new layout.
Did u add the new link between the bottom LM324 pins 7 and 10?
The new cut next to 4013's pin 7?

[ozzy]

It finally works!!! Somehow I managed to miss a hair-thin bridge at one of the cuts.

Alex, thank you so much for your time spent helping me out!

[andrea83]

Hi Everyone I've been spending some time on this circuit which sounded nice, but not great and with a big "pop" when bypassing. I looked for another schematic and I found a new one which is very similar to the original smd version of this pedal that I bought some time ago.
High Filter is A100K, 2 resistors have different value (33k vs 330k and 4,7K vs 22K), one cap has been added (C6) and the bypass switch omitted.
So I made a new layout with a LPB on the output to boost it if there's reason to, but I left a out with no boost if not wanted.

The grey link I'm not sure about. Could please anyone give it a check? Do you think it could be the solution to some problems? Hope I didn't make too many mistakes!
Thank you!

[andrea83]

this is a new updated layout, there was a resistor and a connection missing
now it's working, unfortunately you have to put volume at max to gain unity, but it's working nice