Micro Sample & Hold potentiometers problem...

[marceloide]

Hello , i gonna try to ask here in english and i ask you a very little of patience for me

My name is marcelo and i live in Paris i have a Doepfer , i build the MFOS VCO and it works fine, and i build a LFO of Yu Synth and it work fine too...

so the Micro S&H is my third project. For this, I decided to redo the PCB because I wanted to do it in one face. completed and tested, procedures to manufacture and assemble each component. once installed on an interim panel to ride it in my modular system. the result at first was: INPUT LEVEL potentiometer: OK. however ... the rate potentiometer malfunctions, made ​​the voltage varies almost imperceptibly up to 50% of the lap, then the variation occurs very fast in a span of a 10% return potentiometer, ending almost no variation again. The potentiometer of the glide simply, does not work. I am available for you to publish all photos of the PCB or something else requiring, as it not being electronic I have no idea what can be the problem thank you very much in advance

[marceloide]

here is a jpeg of my PCB , so i think there is no problem about it??? [/img][/url]

[elmegil]

The PCB layout appears to be correct.

You should verify all your component values, including the pots. Also triple check for shorts and things.

If you etched this yourself, look it over with a magnifying glass and make sure there aren't any bits that are over or under etched, leaving shorts or open circuits that may be hard to see with the naked eye....

[marceloide]

[elmegil]

You can test the pots that are wired as rheostats by leaving the power off and measuring that they change with your meter. Due to other circuit components, they may well not show up as the nominal value, but you should at least be able to measure the change....

[marceloide]

hello

i was able to fix the problem but unfortunately it was R14 . unfortunately I had to connect it in backwards as described on the website and then all the beauty of the glide sarted to work, i changed too R16 by another pot of 470k and the the way between min et max of rate is much more homogeneous

[marceloide]

Well, after doing all the tests, and having mounted the PCB, the result is rather mediocre. anyway both potentiometer "saple rate" (1M linear), such as the "glide" (1M audio) malfunctioning. as I said above, this "sample rate" (R16) evolves in an irregular manner, lafrecunecia remains very low throughout 75% of the length of the resistance increases and suddenly, in the remaining 15% to 100%. the glide (R14) is very, very disappointing and has the same problem of R16 as you have said, the PCB designed by myself seems to have no problem, but I will try to make a version MFOS ​​to see if that is not the problem.

thankyou and thanks google traductions

[marceloide]

... and I forgot it : cv out with glide is always OFF ; nothing happend