Author Topic: Troubleshoot PT2399 Delay  (Read 485 times)

FootSolder

Troubleshoot PT2399 Delay
« on: September 01, 2021, 12:24:53 PM »
I built a PT2399 delay on Vero and loved it, so I built another exactly the same but there is no effect when engaged - just passes the unaffected signal and the controls have no effect. Checked tracks, wiring, component values and orientation - no issues. Lastly, I compared the pin voltages between the two boards, all were the same except for Pins 13 (0) and 14 (6.4), instead of approx 3 v on the working version. According to the data sheet these are the low pass filter in/out pins. My question is how to use this info to trace the problem? I'm a newbie but I really want to be able to troubleshoot builds beyond the usual checks. Thank you!

(The layout I'm using https://tagboardeffects.blogspot.com/search?q=transport)

Mark Hammer

Re: Troubleshoot PT2399 Delay
« Reply #1 on: September 01, 2021, 01:50:09 PM »
Wouldn't that suggest that you've somehow either mis-installed  or damaged the 5V regulator?

FootSolder

Re: Troubleshoot PT2399 Delay
« Reply #2 on: September 01, 2021, 03:57:21 PM »
That's exactly the kind of input I was hoping for, thanks! I will try switching it out

Mark Hammer

Re: Troubleshoot PT2399 Delay
« Reply #3 on: September 01, 2021, 03:58:59 PM »
Well don't try running the PT2399 on 9V!

FootSolder

Re: Troubleshoot PT2399 Delay
« Reply #4 on: September 01, 2021, 04:38:13 PM »
That was interesting, I switched out the 78L05 (checking the pinout) and the pedal was the same (just passed unaffected signal) but there was a load of clock noise and whining that changed with the Time control. Figured I might have fried the PT2399, so popped in another one. The signal is quiet again but still no delay. I'm assuming the voltage is not the issue?

anotherjim

Re: Troubleshoot PT2399 Delay
« Reply #5 on: September 01, 2021, 05:11:17 PM »
Pin13 shouldn't read differently from pin2. You might have a short to ground somewhere. Once that is fixed, pin14 should follow at the same voltage. No pin should read higher than pin1. If it does, it suggests it's being pulled up toward 9v due to another short.
Croeso i Diystompboxes.

Comma a question.

FootSolder

Re: Troubleshoot PT2399 Delay
« Reply #6 on: September 21, 2021, 05:27:30 PM »
Oh, man, this build is killing me. After hitting a dead end, I built a completely new board (checking values as I went) and got the exact same issue of an unaffected signal. Changed the PT chip out about 4 times, no change. Finally changed the foot switch and still got no delay but if I dime the Tone control, the pedal goes into crazy self-oscillation and circuit-bent howls. Bad pot?