Madbean Zero Point SDX not working as it should

[Battery Acid]

Hi there guys,

I had a ZPSDX board lying around for some time and decided to finish it today. I had triple checked everything, resistor values, capacitor positions and values, diodes, etc etc, and this think sounds plain weird. I can't get it to delay like erm, a delay pedal should. It sounds like a reverb, and with the feedback at, I don't know, 1/3 of its turn, it starts self oscilating like crazy. I already checked both PT2399 on my Sea Urchin, and they're both working just fine there. The only substitution I have made is 100kB for the mix pot, since I don't have any spare 50kB. If anyone can point me out a direction, I would love to rock this thing out!

[jimilee]

So is your complaint about the sound or the runaway oscillations? If you hit the slam switch does it stop? As far as the sound, I have found the reverb type sound to be normal unless you use the tape selection. I don't care for it either, but that's how it sounds as opposed to the sea urchin or even the cave dweller.

[Battery Acid]

No no, I know it is not working as it should. The delay knob changes the pitch of the sound as I turn it, but I can't get it to repeat notes like my DBD clone, it just oscilates like crazy or gives me a very short slapback. And it happens in every mode, but one of them (wich I don't remenber right now) needs more feedback to oscilate, but doesn't sound like a delay at all. I can hear the ambience and all, it just sounds like a veeeery short delay

[jimilee]

Well that's a neat trick. The delay changes the pitch? are you sure that's the delay and not the rate knob for the modulation? Got voltages and what not?

[Battery Acid]

Oh, I think every pt2399 based delay changes the pitch when you turn the delay knob, the MidFi Electronics Pitch Pirate does this. I'll measure the voltages later and post it here! Thanks in advance

[muddyfox]

As much as I'd like to, I really can't help you out right now as my zpsdx board is scornfully staring at me still unpopulated, but I'll keep my eye out on this thread. I hope for your sake you get to the bottom of this before I put the project together... 

[jimilee]

Oh, I think every pt2399 based delay changes the pitch when you turn the delay knob, the MidFi Electronics Pitch Pirate does this. I'll measure the voltages later and post it here! Thanks in advance

oh well while you're turning the knob, yes. I thought you meant something  else. My bad. As far as the runaway oscillations, does pressing the slam switch make it stop? I had that issue, took three switches before I found one that was nc

[alanp]

Solder a 100k resistor across lugs 1 and 3 of the 100kB Mix pot to bring it to 50kB (correct specced value.)

Also, the build doc states to omit R45, which you've soldered onto the board.

[rullywowr]

Also, the build doc states to omit R45, which you've soldered onto the board.

+1!  Sharp eye Alan.

[Battery Acid]

I don't think the 100k pot could be the cause for the problems, but I completely forgot 'bout r45, I'll try it right away! Thank you!

[DutchMF]

In the last pic, it looks like you might have damaged the board just above D2, D3 and C47, left of C48. Are the traces in that area still connected?

Paul

[Battery Acid]

Well, I just snipped out R45 and no dice, still acting like a reverb and oscilating like crazy with the feedback pot after 1/3 of the turn. Any clue 'bout the area of the circuit I would be paying more atention? I mean, I know it's a verified circuit (like everything madbean sells) and it sounds pretty good, at least on the user's demos. I think I'm just tired from messing with this circuit all day long, maybe I'll take on day or two away from this pedal, but I'm open for ideas 'bout whats causing it to act like this

[Battery Acid]

In the last pic, it looks like you might have damaged the board just above D2, D3 and C47, left of C48. Are the traces in that area still connected?

Paul

I've just checked the board, at first glance it seems to be ok. I'll check the continuity with the Multimeter tomorrow, but I have a strong feeling 'bout the problem being caused by some wrong resistor or capacitor value. But it's just a guess

[Battery Acid]

I checked the continuity and it's ok... tomorrow I'll measure the voltages and post here. do you guys have any other ideas?

[Battery Acid]

Ok, here are the voltages...

IC 1:
Pin 1: 4.70
Pin 2: 4.30
Pin 3: 4.67
Pin 4: 0.00
Pin 5: 4.68
Pin 6: 0.00
Pin 7: 4.70
Pin 8: 9.44

IC 2:
Pin 1: 5.05
Pin 2: 2.51
Pin 3: 0.00
Pin 4: 0.00
Pin 5: 2.79
Pin 6: 2.43
Pin 7: 0.84
Pin 8: 0.90
Pin 9: 2.51
Pin 10: 2.52
Pin 11: 2.52
Pin 12: 2.51
Pin 13: 2.52
Pin 14: 2.53
Pin 15: 2.52
Pin 16: 2.52
         
IC 3:
Pin 1 : 5.06
Pin 2: 2.51
Pin 3: 0.00
Pin 4: 0.00
Pin 5: 2.73
Pin 6: 2.42
Pin 7: 0.87
Pin 8: 0.93
Pin 9: 2.52
Pin 10: 2.52
Pin 11: 2.52
Pin 12: 2.52
Pin 13: 2.52
Pin 14: 2.52
Pin 15: 2.52
Pin 16: 2.52

IC 4:
Pin 1: 4.71
Pin 2: 4.72
Pin 3: 4.66
Pin 4: 0.00
Pin 5: 4.69
Pin 6: 4.72
Pin 7: 4.72
Pin 8: 4.72
Pin 9: 4.72
Pin 10: 4.63
Pin 11: 9.44
Pin 12: 2.30
Pin 13: 4.72
Pin 14: 4.72

I just checked every resistor in the circuit, and all the codes match. Also looked for solder bridges, but no dice. If any one can give me any direction, where I should be looking at, it would be VERY helpfull, I'm very frustrated right now.