tremulus lune troubleshooting

[brokenstarguitar]

I just finished a Tremulous Lune and im having some issues. I get a bypass signal fine but when i turn the effect on it doesnt do anything. I can hear the guitar but its low and no effect. The led flashes as it should and the controls seem to be working being the led tempo chages. I used the commonsound layout with the external gain pot and symmetry mod. Has anyone else had an issue like this? Can someone point me in the direction of what my issue could be? Thanks.

[GibsonGM]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[brokenstarguitar]

the layout is the DIY board at the bottom.
http://www.commonsound.com/kits/doku.php?id=commonsound:tremulus

Here's the voltages.
Battery at the board. 7.64
JRC4558D
1. 3.40
2. 3.40
3. 3.40
4. 0
5. 3.20
6. 3.45-3.50
7. 3.40
8.7.29

TL072CP
1. 3.63
2. 3.63
3. 3.61
4. 0
5. 3.61
6. 3.63
7. 3.63
8. 7.28

Photocoupler:
led- 1.11
led+ 2.22

ldr top. 3.63
ldr bottom. 3.63
battery at the board 7.64

[GibsonGM]

Your IC voltages seem ok.  Have you tried audio probing it?   
http://www.diystompboxes.com/pedals/debug.html

You should listen to the level of signal at outputs of the chips...TL072 pins 1 and 7.   See where it goes kablooey and gets really tiny.   I'm looking at the Tonepad schematic, by the way....your link doesn't give one.   The '72 is for audio, 4558 is for the LFO. 

Totally re-check the wiring to the mod - that's a likely place to make a mistake!   It's also really easy to reverse the input/output wires at the switch - you may have to undo the wires there and just diagnose the board without the true bypass setup... I always check a new build before doing the switch so I know where i made a mistake, if it does this!  If something is grounding when you switch into the circuit, there would be the problem...trace it all, and be sure the switch is 'oriented' correctly (easy thing to mess up).   

Is your photocoupler the one recommended/supplied, or did you make your own?

[PRR]

> schematic, by the way....your link doesn't give one.

There is; but you have to look for it. http://commonsound.org/tremulus/tremulusscheme.pdf

Even before audio-tracing, it looks easy and clue-ful to put a 5K or 10K resistor across the "CdS" photo-resistor. That should give a strong constant output. If a dumb resistor works, but the photo-R doesn't, yet the LED blinks, then suspect the photo-R.

[GibsonGM]

> schematic, by the way....your link doesn't give one.

There is; but you have to look for it. http://commonsound.org/tremulus/tremulusscheme.pdf

Even before audio-tracing, it looks easy and clue-ful to put a 5K or 10K resistor across the "CdS" photo-resistor. That should give a strong constant output. If a dumb resistor works, but the photo-R doesn't, yet the LED blinks, then suspect the photo-R.

Good trick, Paul, I did not think of that