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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
MFOS VCO PWM problem
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The Bad Producer



Joined: Mar 08, 2009
Posts: 255
Location: The Manhole

PostPosted: Sun Feb 17, 2013 6:05 am    Post subject: MFOS VCO PWM problem Reply with quote  Mark this post and the followings unread

Hello people,

Hoping someone can chime in and help!

I've just built the MFOS VCO, with recommended part changes for 15v operation, and all is working as it should, apart from one important thing!
The PWM seems to be buggered, if the PWM pot is turned all the way CCW then I can hear all waveforms apart from PULSE output, when I turn the pot CW the PWM seems to affect the timbre/frequency of all the waveforms until at a certain point the VCO stops oscillating (dies basically) until I turn the pot back CCW... It's like the PWM stops the core working above about 60%?

The PULSE out works when pot is just off CCW and again, PWM affects the output until it dies (around 3 'o'cock)

I've double checked parts/wiring/reheated solder etc.. I'll keep probing today with the scope, but it does seem odd to me!

Any ideas?

Shall I just dump the PWM feature?! hahaha

Cheers

Charlie

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elmegil



Joined: Mar 20, 2012
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PostPosted: Sun Feb 17, 2013 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

You're checking the right stuff...you might look at component values too. I've had some really silly mistakes in some boards that I looked at repeatedly until I realized what was wrong.
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The Bad Producer



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PostPosted: Sun Feb 17, 2013 8:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi elmegil, thanks, but yeah - I printed out the component overlay and went through with a magnifying glass double checking and ticking off!

Slightly confusing with the different revisions of the PCB's too, but I think I'm on the right track... Just built the CGS VCO too, and no problems with that, even though it is a slightly more complex build!

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