I could use a hand debugging a rebote 2.5.....

[bernierunns]

Hey, I hope this isn't against the forum rules but I'm at a stalemate with this pedal, I've been debugging it for about a week on my own and I could use some help.

The layout is at http://tonepad.com/getFile.asp?id=98

I am running off a one spot power supply. I have a clean signal when bypassed but no guitar signal when the unit is turned on. I can hear the delay working on the "pop" of the guitar cable being plugged in though. And it is responsive to the repeats knob, meaning it fades faster as the repeats knob is turned down. I have checked for continuity on the red, orange, green and grey paths on the layout. It is the blue path (input) path that is giving me trouble. I don't have a signal after .082 cap right past the input connection. So the 510k resistor is not getting a signal from what I can tell. I swapped out the cap in question (.082) and still nothing. What do?


My voltages are as follows and from what I can tell are pretty close to normal.

IC PT2399

1. 4.94
2. 2.46
3. 0.0
4. 0.0
5. 2.61
6. 2.46
7. 0.22
8. 0.83
9. 2.46
10. 2.51
11. 2.47
12. 2.46
13. 2.46
14. 2.46
15. 2.46
16. 2.46

IC TL072

1. 4.80
2.4.78
3. 4.75
4. 0.0
5. 3.90
6. 4.79
7. 4.79
8. 9.53

IC L78L05

E 9.53
B 0.0
C 4.94




 
 
 

[GoranP]

Just to kick things off, I suppose you are using an audioprobe?

When you use it on both ICs, are you getting anything resembling your signal on any of the IC pins (especially the opamp)? Contrary to what little I remember of circuit theory, there have been occasions where I'd "lose" signal where I'm quite sure signal should be present, only to have it for instance appear again at the opamp input.

And you are saying that the "pop" is getting repeated and responsive to knobs?

Right now if this was vero I'd be thinking a solder bridge but from all the shadows on the pcb I just can't tell.

[GoranP]

And also, eventhough your ICs appear to be alive and well, you really should use sockets... what if one of the ICs dies and you need to swap it out....

[bernierunns]

When probing I get signal fro pins 5 and six on the TL872 and pins 12-16 on the pt2399.

[GoranP]

If you had your ICs socketed, I'd suggest swapping out the opamp. It's strange to have signal at input and no signal at output (pin7), especially if you have voltage on pin 7.

Also, are you measuring with pots fully cw? pin 7 should be slightly higher than 5/6.