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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Micro Sample & Hold potentiometers problem...
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marceloide



Joined: Feb 06, 2014
Posts: 6
Location: paris

PostPosted: Sat Feb 08, 2014 4:38 pm    Post subject: Micro Sample & Hold potentiometers problem... Reply with quote  Mark this post and the followings unread

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

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
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marceloide



Joined: Feb 06, 2014
Posts: 6
Location: paris

PostPosted: Sat Feb 08, 2014 4:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

here is a jpeg of my PCB , so i think there is no problem about it??? Posted Image, might have been reduced in size. Click Image to view fullscreen.[/img][/url]
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elmegil



Joined: Mar 20, 2012
Posts: 1507
Location: Chicago
Audio files: 14

PostPosted: Sat Feb 08, 2014 10:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

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....
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marceloide



Joined: Feb 06, 2014
Posts: 6
Location: paris

PostPosted: Sun Feb 09, 2014 8:41 am    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
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....


thank for your answer

i verify all components values yet (almost three times before !) ,

there was an error about a resistor that must be 75k and i bought a 75ohms one, so i put two 150k resistors in paralel that gave me 75k ; with a magnifying glass i dont see any short,

im gonna test the potentiometers but before i think i must to extract them , i dont know how to test a potentiometer but i will learn it on internet , the only problem is that potentiometers R14 and R16 are welded in a special way... so i must to undo it that before le test
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elmegil



Joined: Mar 20, 2012
Posts: 1507
Location: Chicago
Audio files: 14

PostPosted: Sun Feb 09, 2014 12:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

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....
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marceloide



Joined: Feb 06, 2014
Posts: 6
Location: paris

PostPosted: Fri Feb 14, 2014 11:46 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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marceloide



Joined: Feb 06, 2014
Posts: 6
Location: paris

PostPosted: Tue Feb 25, 2014 9:55 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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marceloide



Joined: Feb 06, 2014
Posts: 6
Location: paris

PostPosted: Wed Jul 23, 2014 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

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