pt80 was working, now dead, can any one help ?

[znowman]

ive built 2 pt80s now, the first one (mine) works fine, the second one (built for a friend) did work, even in the enclosure, but after i gave my friend the enclosure to paint, when ive come to reinstall, theres no delay...

heres some info:

ive built the pt80 from the GGG site, with the exact parts values and no mods
im using 18v power, and its reaching the board
im getting sound when the effect is on, and when bypassed, but no delay effect

ive been probing around the board comparing things to my working version, and most things seem the same or very similar, the only thing that seems to be wrong is leg 2 from the 'repeats' pot, it is not connected to ground and neither is the track on the board which leg 2 is connected to

heres an image of the layout which shows what im going on about:



im using the audible buzzer on my meter to check connectivity, ive got the black probe at the dc socket on negative and the red probe on leg 2 of the pot, which as i say is giving no buzzer

so my question is this, is leg 2 of the pot grounded through leg 1 or is it grounded from the track on the board.  i think (and hope) its a broken pot

any help is much appreciated, as this is only my 3rd pedal, im pretty stuck

[znowman]

anyone ?       before i start ripping things apart and then resoldering....

no seriously, i just made an (ingenious) audio probe, although im struggling with the schematic  , i'll try and follow the circuit

[znowman]

i got angry and threw the thing in the bin (me and my temper) - thanks anyway

[Auke Haarsma]

Well, if the bin isn't too deep/dirty I'd get it out. Clean it and post the voltages you measure on the PT2399.

[znowman]

i made one of those audio probes and as i was probing around got a spark and then a decent amount of smoke     i think its well beyond me being able to resurrect, and probably easier to start again from scratch

although i find it very interesting, im not sure electronics is for me

thanks again though

[Auke Haarsma]

yeah I can imagine feeling like that. I've smoked quite some parts too But I got hooked anyway. Once you get an effect up and running the satisfaction is really huge.

If you don't feel like debugging (I've build a PT80 too, so I could offer some help if you decide to give it another shot) at least keep the populated pcb somewhere. Maybe you'll have another look later on.

Gl anyway!

[znowman]

you are right, and ive retrieved it now, maybe a few days without looking at it will put me in a better frame of mind.  i think the annoying thing is that it worked perfectly when i first fired it up.
im pretty sure it was an electro cap which i was probing at the time that smoked, or was it the nearby transistor    hmmm....

ill give it another chance, will definately be a challenge (with my inexperience) to get it running

[Auke Haarsma]

Feel free to post here or remind me via PM if you feel like debugging again!

[znowman]

thanks for the offer, i'll post back here if i get stuck
thanks again, i appreciate it

[lynessmy]

PT2399 is a CMOS and it is dang sensitive to ESD.
I had build REBOTE 2 and todate, i had at least 4 PT2399 with suddent death due to this. 
I didn't have enclosure for it. So, I know i had this again when i observed either of these.

1. Weak ECHO / DELAY signal.
2. No Delay at all but play clean sound when the pedal is on.
3. high distortion, even with short delay time.
4. no output when the pedal is on.

So, when you work around with the PCB, make sure you at least follow this general safty precautions.

Never solder the board with the IC plugged in, never even you are not soldering IC pins.
There is even suggestion to switch off the iron when soldering the CMOS IC pins. But if you are using IC socket, i think this is overdone.
Make sure to unplug signal or power cable only after you shut it down totally.

Take good care to prevent ESD or sooner or later...you are gonna fail another chip.