Help with tonepad phase 90

[elflicho87]

Hi everyone, I'll try to follow the suggested procedure...

1.What does it do, not do, and sound like? Pretty strange things are happening: the effect works right when I start playing with it, than, after 1 minute or 2 of use it stops phasing and it only adds some sparkle and clarity to the sound.

2.Name of the circuit = Tonepad Pez 90
3.Source of the circuit (URL of schematic or project) = http://www.tonepad.com/getFile.asp?id=42
4.Any modifications to the circuit? Yes, I added a flashing LED from pin 7 of IC1 to switch trough a 2k2 resistor.
5.Any parts substitutions? Yes I've used six 0,047uF in place of the six 0,05uF, and a 10uF instead of the 15uF
6.Positive ground to negative ground conversion? No
7.Voltage at the circuit board end of the red battery lead =9,52
   Voltage at the circuit board end of the black battery lead =0,00

Ok, voltages now

Q1
D=4,83
S=4,94
G=0,64 to 0,82


Q2
D=4,83
S=4,94
G=0,64 to 0,82

Q3
D=4,82
S=4,94
G=0,64 to 0,82

Q4
D=4,83
S=4,94
G=0,64 to 0,82

Q5 2N4125
E=4,94
B=4,33
C=3,25

IC1
1 4,88
2 4,88
3 3,30
4 0
5 3,66 to 5,32
6 4,84 rate at min/ 5,02 rate at max
7 1,33 to 8,18
8 9,49

IC2
1 5,01
2 4,95
3 4,84
4 0
5 4,84
6 4,95
7 4,88
8 9,51

IC3
1 4,99
2 4,94
3 4,83
4 0
5 4,83
6 4,95
7 4,92
8 9,49

Zener diode (5,6V)
A 4,94
K 0,00

Any help would be really appreciated
thanks!
Nic

[Govmnt_Lacky]

No change when adjusting the trim pot?

[elflicho87]

Thanks for the reply, Govmnt_Lacky
well, I forgot to say that I used a multiturn 220k trimpot (instead of 250k) and it's set full clockwise... when i turn it counterclockwise the phasing effect gets weaker. I'm gonna change it one of the next days, anyway, but I don't think that's the problem...
re-reading my first post I noticed I should have said:"every time I plug the effect, it works right the first few minutes, and then, no more phasing"
argh!!!
Nic

[PRR]

You have to get those Gates up close to +5v.

You have a part-volt there. What are the voltages on the trimmer? One end should be zero, the other +5V, and the third pin should turn from zero to 5V.

Do you get that trim voltage on the 1Meg resistor?

Did you buy the PCB from TonePad or roll your own?

Lift one leg of the 3.9Meg and the 0.05 cap in the corner. Now the trim voltage should appear on the FET Gates. Does it?

> every time I plug the effect, it works right the first few minutes, and then, no more phasing

It would be a good clue if you could just watch key voltages such as FET Gates over the first minute and see what changes.

[Govmnt_Lacky]

A couple things to get you started and going with what Paul mentions:

1) Double check ALL of your resistors, capacitors, and other components for the proper values and orientation. (especially any tantalum or electrolytic caps)

2) Make sure that your trimmer pot is installed CORRECTLY. Ensure that you do not have the trimmer wiper pin (Pin 2) installed in the wrong spot.

If you are still having problems, I recommend posting some pictures of your build. May help to spot problems with fresh eyes 

P.S. Are you sure that ALL of the jumpers are installed?

[elflicho87]

Ok, got it working!
I replaced the trimmer, and everything turned fine... still I can't understand what was going on before I replaced it
anyway here are some pics
http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg835580#msg835580
as you can see it waited a whole month before I spend a little time on it trying to get it working
thanks for the help guys!
Nic