Help with PT-80 delay - No wet signal

Started by Swoon, August 17, 2009, 06:32:09 AM

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Swoon

Hi,

I have built a PT-80 delay (Scott Schwarz design) with onboard charge pump.

The problem is that the only output I get is the same as the bypass signal. No reaction from the pots what so ever and no audible delay.
I already double checked all external wiring, swicth, IC Layouts, cap polarity etc... This seems to check out...The led switches on when the switch is pressed.

It was built according to the following project file: http://www.uk-electronic.de/Download/Beschreibung%20PT80.pdf (German, but the schematics and layouts are there...)

These are the voltage readings I get:

Power supply:
---------------
9,27V

7660S- Charge pump:
--------------------------
1: 9,27V
2: 2,26V
3: 4mV
4: -4mV
5: 3,7mV
6: 3,04V
7: 3,84V
8: 9,27V

TL072:
-------
1: 5,28V
2: 5,28V
3: 5,28V
4: 1,2 mV
5: 2,63V
6: 5,29V
7: 5,28V
8: 10,55V

PT2399:
----------
1: 5,04V
2: 2,52V
3: 3,7 mV
4: 3,6mV
5: 1,30V
6: 2,34V
7: 0,5V
8: 0,74V
9: 2,53V
10: 2,53V
11: 2,53V
12: 2,53V
13: 2,53V
14: 2,53V
15: 2,53V
16: 2,53V

SA571N
---------
1: 0,70V
2: 1,80V
3: 1,80V
4: 2,7 mV
5: 1,14 V
6: 1,11V
7: 1,11V
8: 1,81V
9: 1,81V
10: 1,14V
11: 1,20V
12:1,22V
13: 10,52V
14: 1,80V
15: 1,80V
16:36,1mV

How can I verify if the power going out of the charge pump section is actually ok? Where would I be able to test that?
Anything else I can check according to these reading?

Thanks,

Stefan

rm -rp ./Matt*

check the voltage at the input stage of the 2 voltage regulators 78L12 and 78L05, both should have ~17 volts going into thanks to the charge pump.
-- keh keh yeh.

Swoon

Weird:

78L12
--------
I: 11,94
C: 0
O: 10,42

78L05:
-------
i: 9,28V
c: 0V
o: 5,05V

Does the circuit stay numb when it isn't fed 12V? It seems my regulator only throws out 10,42V...


Swoon

I've found the problem.

First I replaced the 7660S on the charge pomp cirquit. This boosted the voltage to normal levels.
After that still no delays.

I traced the signal using an audio probe and noticed that the SA571 wasn't outputting anything.
I replaced that IC as well and everything works fine now.

Still got me thinking though, 2 of the 4 IC's that were delivered with the kit seemed to be busted.
Or I've got poop in my fingers :) One of both... :)

Thanks for the help!