Orange squeezer problems

[bagudan]

HI. I´ve made an orange squeezer. My second one. First one works just fine.
The second one is made from this layout:

http://www.aronnelson.com/gallery/main.php/v/diyuser/Orange+Squeezer.gif.html

It acts like a noisy boostpedal. The volumeknob is working, but the trimmer does not make any difference, nor can it make the sound dissapear... as it is supposed to do?

Voltages
Q1
d-9v
s-3,4v
g-2,6v

q2
d-1,7v
s-2,6v
g-0v

IC (tl072)

1-5,6v
2-5,6v
3-5,6v
4-0v
5-0v
6-9v
7-9v
8-10v

The voltages on the ic sems way off, when I compare to the guide from generalgutargadgets:
http://www.generalguitargadgets.com/pdf/ggg_osq_instruct.pdf?phpMyAdmin=4a28f86a515b7883e7bc35a68d4e7b6d&phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Components,traces, cuts and soldering have all been checked carefully! What am I missing here?

Thanks
-Kasper

[Tony Forestiere]

R6 is Missing from the board? The BOM shows three 470K resistors, two of which should be used to generate Vref. (I am guessing, but those are the only duplicate values). R8 looks like it is doing it's thing from GND to pin 3. Where is the complement R6? Your voltages differ because (to me) it looks like Vref bias is messed up.

...Although I am probably wrong

[bagudan]

R6 is at the bootom of the board, left side, from the gate of the tranny, and two strips down.
-Kasper

[Earthscum]

According to the GGG listed voltages: Your Q1 looks close, but your Q2 looks like the Gate and Drain are about .6V low. I'm getting ready to build one of these, so I can't really help you much other than simple observation. I may be hijacking your thread in the future to debug my own, lol.

Good luck.

[bagudan]

Well, it works now. Replaced the trimmer. I guess the trimpot was broken? voltages on the transistors are fine, voltages on ic-pins are still not like like the ones at ggg, but maybe the layout is different, using the other half of the opamp? I don´t know, not that good with schematics
Anyway, it works and sounds sweet!

[Earthscum]

Well, it works now. Replaced the trimmer. I guess the trimpot was broken? voltages on the transistors are fine, voltages on ic-pins are still not like like the ones at ggg, but maybe the layout is different, using the other half of the opamp? I don´t know, not that good with schematics
Anyway, it works and sounds sweet!

Aye, I'm sorry... I forgot to mention that. I noticed when looking at your voltages, exactly what you said... one layout is using the other half of the amp.

Glad to know ya got it working! I wouldn't have suspected the trimmer (although I know better... check your mechanical parts first, i.e. solder joints, traces, pots, etc.). You probably just got a bit too much heat on the first round. I've trashed a couple pots and trimmers that way. One trimmer actually acted like a short, so I pulled it. Turned out flux had flowed into the track and some solder decided to run with it and stick to the wiper and made a big solder smear across the track, turn to turn.

Think I'm gonna have a showdown with the OSQ board tonight. Looking forward to it  (if I can keep off the Nurse Quacky... maybe enough coffee will get them both done.)

[bagudan]

Hope you get yours working! This layout works well, but compared to my other squeezer (etched pcb fom ggg), this one is much noisier, when using a wallwart for power supply. Dead silent with a battery though!