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Hi Garfo !
I guess that you have soldered the rotary switch to the wrong side...take a look to the ZP build guide :

http://www.madbeanpedals.com/builds/reports/zpsdx/index.html

good luck 

...and I learned what an audio probe is and how to use it !
I have to say that this boards are very good quality, I have soldered and desoldered and soldered back several components which can be tricky in a double sided PCB...
I guess I'll sleep peacefully tonight.

thanks ! yes, it feels good !
What did I learn from this ? well...never build something difficult when my wife is talking to me... 

...et voilà !!!
Yesterday evening I took all pots off to see if I could find something and nothing...so I decided to desolder every electrolytic , diode, and check again all the rest of the caps...Today, after work I found the problem : I put a 10nF in place of a 100nF for C26...
I feel super stupid and happy at the same time...It took me only 30 minutes to put all together...and voilà : my second Zero Point SDX works and sounds as good or better than the first one !!!

Thank you for your help,

Pierre

...no, my fdbk pot is a 50Kb...and yes, modulation is working...rate led blinks and all... with the mod switch engaged  the distorted motorboarding noise gets some sort of modulation, that varies as I turn rate and depth pots...After checking all resistors values and looking for shorts and solder bridges I think I have 2 things left to check...all caps and diodes. I have changed some electrolytic and those 10µF tantalum, just to see if the problem was there, I guess I have to remove pots to test the rest of the caps...I don't know how to check for the diodes, they are all 1n914.
Right now I'm comparing values with diodes installed in the working ZPSDX...all of them are around 0.560v in my multimeter...don't see anything strange here...

I have done some more testing...change all ICs and transistors and the problem still there...
One thing that I've noticed is that the feedback pot goes from 1 dirty repeat when is full turned off to self feedback (I really don't know how to put it in words) when I turn it just a little (like at 9:00)...more exaggerated when ghost is on...I should post some sound samples but right now it's a little complicated...
Next thing I'll do is take off Delay and Fdbk pots to change some caps...I don't know, I'm lost here

... sorry...with IC2 and IC3 both removed I get clean dry signal in IC2 pin 16...and mute in pin 16 IC3...In fact I get clean dry signal in IC2 pin 16 with or without IC3 installed

I'll check again...

hi !
Removing both IC2 and IC3 I don't hear any signal at IC2 's pin 16...mute. With only IC2 removed I get clean signal in pin 16...
I don't know if this can help but I'm posting some pictures from the solder side...do I have to de-solder the delay pot to show a clearer view?





...looks messy but its only the flux...
Again, thank you for your patience...

So...
I put together a probe and I have done some testing...
With fdbk all the way down and delay and mix pot at noon, no ghost, mod and path engaged...

R8 : (C4 side) clean dry signal, (R41 side) mute
R21:(C29 side) Faint delay signal, (Out side) mute
R12: (C10 side) faint delay signal, (IC2 side) normal? Delay signal
R11: (C10 side) faint delay signal, (IC2 side) mute
R10: (C5 side) mute, (IC2 side) dry signal
R9: mute in both sides
R18: (C16 side) faint fuzzy signal, (IC3 side) distorted gated delay signal
R17: (R14 side) faint fuzzy signal, (IC3 side) muted (i guess, I forgot to note this one )
R16 : (IC3 side) delay signal
R15: (IC3 side) mute

...sides are taken from the layout. Not sure if I'm doing this right, In any case I'll do some more testing tomorrow...
Thank you !

thanks for your replies, I will check with an audio probe as soon as I build one and learn how to use it...
Just one detail :I have soldered a on-off-on switch for  "ghost" ...but I guess that that is not the source of the problem.

  sorry...I did not know what an audio probe was...all this years building effects, I guess I was just lucky...
Right now I'm reading RG's article on how to make (and use!) a probe.

I checked all resistors, nothing wrong here. I know that it is difficult to check a resistor value that's allready soldered in a circuit, but having another ZP working helped me to compare...I usually check all resistors with a multimeter before solder...the same with caps, so I was pretty sure that the problem wasn't there.

yes, r45 is omitted as noted in ZPSDX documentation update...
I'm checking resistors values one by one, but still not finding the source of this problem...

more pics, now with IC4 and R28 installed...(to many pictures? )

I hope this will help...









C18 is a 2n2 Panasonic's cap (I did not have any more boxed ones)
C22 and C11 were changed to electrolytic
IC4 (removed) has a 16 pin socket which I put by mistake, so R28 is socket ed (removed in the picture)...