Zero Point SDX help (please) SOLVED !!!

[pierre67]

Hi !
I'm Pierre, this is my first post here...but I was reading around for a while...
Yesterday I build my first Zero Point SDX which worked right away; as I had a spare board and enough parts to build another one, today I decided to do it. The only thing different with this one is the caps, I wanted to try some Wima caps to see if they would make any difference in the sound. This one don't work  
The sound is gated and there is an aw full motorboarding noise...I can tell true the noise that control knobs do what they are suppose to do, as well for the switches...

I have done some voltage readings in the IC's if it can help :

IC1
1  4.77v    5  9.54
2  4.77      6  4.78
3  4.75      7  4.78
4  0.01      8  4.15

IC2 and IC3 same readings
1  5.02        9  2.52
2  2.5         10  2.52
3  0.01       11  2.52
4  0.01       12  2.52
5  1.28       13  2.52
6  2.45       14  2.52
7  0.28       15  2.52
8  0.80       16  2.52

IC 4
1  4.77        8  4.77
2  4.77        9  4.77
3  4.68       10  4.75
4  9.54       11  0
5  2.34       12  4.75
6  4.77       13  4.77
7  4.77       14  4.77

IC 5
1 between 2 and 5?
2 4.77
3  4.54
4   0
5  9.54
6  between 2 and 7 ?
7  4.54
8  3.97

Any toughs?
Thank you !!!

[madbean]

Voltages look good. Is the motorboating in all delay settings? What about if you turn the Mix knob all the way down?

[pierre67]

Hi !!!
Yes, motorboarding in all settings. By the way the rate led works.
I allready checked for solder bridges, electrolytic caps orientation and everything seems fine...

[madbean]

Hmm. Next I would try removing some ICs and see if the motorboating goes away.

First remove the two PT2399s and listen to the dry signal. If you still have motorboating, removeIc5 (the modulation one).

This will help narrow down the area that is causing the problem.

You can also audio probe to see where the noise is coming from. Listen to pin1 on IC1A, pins 16 and 15 on both the PT2399s (with the ICs inserted back in).

[pierre67]

sorry...i did not answer completely...With the Mix knob all the way down the noise disappears and my dry signal sounds fine...

[pierre67]

update: the noise is gone when i remove IC 3
...audio probe..? way out of my skills 

[pierre67]

me again...
Let me try to explain a little better the problem...With feedback knob all the way down I get 1 repeat that sounds very distorted and gated, sounds allmost farty. Delay pot does work, it delays the farty sound and mix pot does what it does, increases the level of the flatulence  ...As i turn feedback up, that single farty repeat turns to a motorboarding sound...like a long fart...I can tell that modulation works to as I can hear that the noise (the farty sound) wobbles (and led indicator is blinking and varies as I turn up the rate pot).
Slam does work too.
As suggested, I removed one at the time ICs 5, 3 and 2. The noise stopped when I removed IC3...getting only dry signal.
I tried changing all ICs and transistors, change all caps around IC3, checking diodes and caps orientation, solder bridges...and nothing...Next step is, I guess,to remove pots to check if there is not something wrong under them (but I doubt it)...

With all this frustration I forgot to mention that the first one sounds awesome.

What should I check next?
In any case thank you for your help and your patience, I know is not easy to read such a complicated description from somebody that actually do not speaks English very well... (spell check does miracles)

[madbean]

I'm going to guess you have an incorrect resistor value somewhere, but I'm not positive yet that is the issue. Can we have a clear pic to the top side of your build, please? I'd like to see two close up shots: left side and right side. Particularly, let's look at those resistor values around IC3.

[pierre67]

I'm taking a few pictues right now...i'll post'em in 5 min.
Thank you again !

[pierre67]

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)...

[pierre67]

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

[wgc]

Is r45 supposed to be missing?

[pierre67]

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...

[midwayfair]

An audio probe is VERY easy to make and it would make it much easier and faster to track down the location of the problem. It's just a capacitor soldered to the tip wire of a cable, and then a wire to ground the sleeve. There are instructions to make on in the tech help rules thread.

[gtr2]

http://diy-fever.com/misc/audio-probe/