GGG PT80 PT-80 - none of the pots are working

[rratajski]

I built up a GGG PT-80 Digital Delay.
It worked perfectly and without fail for over a month, then went south.

When I engage the pedal, there is no delay, no volume change, etc. None of the pots do anything to the signal. It's just a clean signal.
I switched out the switch thinking it was a bad switch.
I checked for any ground-outs or leads touching one another.
I remelted and checked for any bridges.
I am running the unit w/ a 9V wallwart. I have tried two different power supplies on different outlets and get the same result.

Can anyone point me in the right direction of where to look?

[Thomeeque]

 Some of active components has probably died (not TL072, it seems to be working, and 7812 as well) - get yourself audioprobe and check wet signal path:

• SA571, pin 10 (if silent from here, 1st half of SA571 has died)
• PT2399, pin 14 (if silent from here, PT2399 has died)
• SA571, pin 2 or 3 (if silent from here, 2N5088 has died)
• SA571, pin 7 or 6 (if silent from here, 2nd half of SA571 has died)

But maybe check voltage at PT2399 pin 1 first by voltmeter, if 7805 still works..

Good luck, T.

[rratajski]

Thanks!
I'll get on that this weekend and report back!

[Thomeeque]

 But wait a minute!

I am running the unit w/ a 9V wallwart. I have tried two different power supplies on different outlets and get the same result.

Did you use same source before? It should be feeded by 15-24V source you know

If it worked and you plan to use 9V even in the future, maybe you should at least remove 7812 and bridge it, to put at least those 9 volts inside..

T.

[WLS]

I am running the unit w/ a 9V wallwart. I have tried two different power supplies on different outlets and get the same result.

Are you running it with or without a charge pump?


Bill

[rratajski]

I built it w/ the charge pump to be able to run the pedal w/ a 9V power supply. Both of my power supplies that I tried were 9V/9.6V.
When the pedal worked (for the month) it was powered by a 9V power supply w/out failure.

http://www.generalguitargadgets.com/pdf/ggg_pt80_lo1.pdf

[WLS]

Can you list your voltages so that we can access what is going on with the pedal? This helps us to help you.

Thanks,


Bill