Zero Point Mini troubleshoot

[HailToTheBlues]

Hi guys,
I finished a zero point mini, but it is not working. When it's off, the guitar has sound, but when i turn it on, i get absolutely no sound. So where should start i looking for the problem? I already checked for polar components soldered in reverse, and i think that my wiring is correct, so any thoughts?

Best regards

[madbean]

Taking voltage measurements and audio probing the inputs and outputs of the IC's are what I would do.

[HailToTheBlues]

I still don't have a tester with a audio probe, but i really need to get one. About the voltages, how should take them? where do i place the leads of the multimeter?

[HailToTheBlues]

One question, is a tl062cn the same as a tl062cp? because i noticed i had a tl062cn installed. Also, this may be nothing but, when i tap on the back of the pt2399 and the tl072cp chips, there's a sound like someone is knocking on a door, but when i touch the tl062cn there's almost no sound. Does that mean anything?

[madbean]

It's fine to use either version of that TL062 or even a TL072. That's not the issue.

For voltages attach the black lead from your DMM to the circuit ground and use the red lead to get the DC voltages from the IC pins.

[HailToTheBlues]

So here are the volteges i measured:

TL072CP
1. 0.26
2. 1.73
3. 3.40
4. 0
5. 3.26
6. 3.40
7. 2.40 - 6.50
8. 6.87

TL062CN

1. 0.65 - 6.20
2. 3.26
3. 3.36
4. 0
5. 3.26
6. 3.40
7. 2.40 - 6.50
8. 6.87

PT2399

1. 4.92
2. 2.46
3. 0
4. 0.09
5. 2.26
6. 2.45
7. 0.16 - 0.30
8. 0.64
9. 2.46
10. 2.45
11. 2.45
12. 2.45
13. 2.45
14. 2.45
15. 2.45
16. 2.46

What do you think Brian?

[madbean]

Your PT2399 voltages look good. The problem is in your VC and VB voltages (referring to the schematic). You should have closer to 8.5 on pin8 of both ICs, and you instead have just above 6v. This appears to impact your VB voltage, too.

Assuming you are using a steady 9v supply, I think you have installed the wrong value on R28. Can we see a pic of the top of your board? I want to see what resistors you have on R28, 29 and 30.

[HailToTheBlues]

So here is the pic you asked for. I also measured the resistors you refered and the R28 is correct, it is a 47R, but the R29 and the R30 are giving me some strange values. The R29 is giving me 6,6K and the R30 is giving me 2,9K, even though they are both 10k resistors, so any clue?

[gtr2]

You can't measure resistors while in the circuit.  Thats why you have strange values.  Likely they are fine.  You would have to pull one leg out of the resistor to measure the resistance properly.

Josh

[gtr2]

I'd also check for solder bridges next to pads that should not be connected....

Josh

[Matt]

If none of the above works you might want to try a different pt2399. I had a somewhat similar issue with the one I just built. The difference was I was getting just over 5.5 volts at vc, 2.7v at vb and around 4 volts at the pt2399. I was getting a clean signal but no delay and the modulation led wasn't working. I tried a different pt2399 and it works fine now.

Good luck!

[HailToTheBlues]

If none of the above works you might want to try a different pt2399. I had a somewhat similar issue with the one I just built. The difference was I was getting just over 5.5 volts at vc, 2.7v at vb and around 4 volts at the pt2399. I was getting a clean signal but no delay and the modulation led wasn't working. I tried a different pt2399 and it works fine now.

Good luck!

The thing is that i don't have sound at all when it is bypassed, and the rate led is working as it should, so i don't know if it is the same issue. Also i purchased the pt2399 from Dr. Tweek, and people here said that he tests his pt2399, so i think it is unlikely that the problem is from the IC.

[Matt]

If none of the above works you might want to try a different pt2399. I had a somewhat similar issue with the one I just built. The difference was I was getting just over 5.5 volts at vc, 2.7v at vb and around 4 volts at the pt2399. I was getting a clean signal but no delay and the modulation led wasn't working. I tried a different pt2399 and it works fine now.

Good luck!

The thing is that i don't have sound at all when it is bypassed, and the rate led is working as it should, so i don't know if it is the same issue. Also i purchased the pt2399 from Dr. Tweek, and people here said that he tests his pt2399, so i think it is unlikely that the problem is from the IC.

My apologies I didn't realize that you were having issues when bypassed as well. I would try to resolve that first.

[HailToTheBlues]

If none of the above works you might want to try a different pt2399. I had a somewhat similar issue with the one I just built. The difference was I was getting just over 5.5 volts at vc, 2.7v at vb and around 4 volts at the pt2399. I was getting a clean signal but no delay and the modulation led wasn't working. I tried a different pt2399 and it works fine now.

Good luck!

The thing is that i don't have sound at all when it is bypassed, and the rate led is working as it should, so i don't know if it is the same issue. Also i purchased the pt2399 from Dr. Tweek, and people here said that he tests his pt2399, so i think it is unlikely that the problem is from the IC.

My apologies I didn't realize that you were having issues when bypassed as well. I would try to resolve that first.

But just to complete my reply, i have no sound when bypassed, but i have normal sound when the effect it's off.

[madbean]

Time for the tough love: did you test it before putting it in the enclosure? If so, and it worked, then concentrate on the bypass switching first. If not, well then you need to take it apart and test just the effect by itself to eliminate the possibility of I/O problems.