SOLVED Seabed Delay - Trouble with PT2399

[issa19]

Hi everyone,

About a month and a half ago, I build a seabed delay kit. Ever since then, it has had this very strange issue: The pedal works completely fine and all features are functional, but if I disengage and reengage the pedal using the footswitch, I only get one repeat, no matter what the feedback knob is set to, until I remove the PT2399 and put it back in.

I have a feeling that its a problem with the PT2399, but I have used four different ones (all from Tayda) and they have the same problem. I have also swapped out the TL072 three times. I have compared my voltages and they seem to be fine, except I'm getting 7.98 for Vcc on the TL072. I have also soldered a bridge between pins 3 & 4 on the PT2399.

 

[zgrav]

what happens if you do not unplug the PT2399, but instead cycle the power to the pedal? (turn it off and back on, or unplug the jack and then plug it back in)?

 

[phi1]

Hmm if I understand your description, I would bet it’s more likely a loose connection or a malfunctioning fdbk pot than the pt2399. The pt chip itself has nothing to do with the feedback. The pt simply takes an input and gives an output a set time later. The echo is then mixed back into the pt input via the feedback pot. So if you’re getting one echo, it seems the pt chip is working ok, and there’s a problem somewhere in the feedback circuit path. Maybe handling from taking out the chip and putting it back coincidentally fixes the loose connection or something.

 

[Boba7]

If you have one repeat, then the chip is working
Your feedback path is the issue I would think, not the chip

You’re getting 8v on pin 3 & 5 of the opamp? That’s another issue, again not linked to the pt2399

Seems to me there’s some debugging to do here

 

[issa19]

If you have one repeat, then the chip is working
Your feedback path is the issue I would think, not the chip

You’re getting 8v on pin 3 & 5 of the opamp? That’s another issue, again not linked to the pt2399

Seems to me there’s some debugging to do here

A little bit of confusion on my part. I get 8V on Pin 8 of the opamp, I was just concerned because its supposed to be around 9V.

 

[issa19]

Hmm if I understand your description, I would bet it’s more likely a loose connection or a malfunctioning fdbk pot than the pt2399. The pt chip itself has nothing to do with the feedback. The pt simply takes an input and gives an output a set time later. The echo is then mixed back into the pt input via the feedback pot. So if you’re getting one echo, it seems the pt chip is working ok, and there’s a problem somewhere in the feedback circuit path. Maybe handling from taking out the chip and putting it back coincidentally fixes the loose connection or something.

Solved! The problem did in fact turn out to be a malfunctioning feedback pot. I switched it out with a spare 50k & re-flowed some suspicious solder joints, and now the problem seems to be fixed. The even itself even sounds better and less noisy after the repair. Thanks for your input!

 

[Boba7]

Glad you got it working!