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 Forum index » DIY Hardware and Software » YuSynth
Too many modules?
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Conboy



Joined: May 01, 2009
Posts: 25
Location: London

PostPosted: Tue Jun 16, 2009 2:30 pm    Post subject: Too many modules?
Subject description: Wierd signals with new VCO
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I have just finished my second VCO and when starting to calibrate things got a bit wierd.
All scope readings were blurred (ie multiple ghosting waves) so almost impossible to set. Thought my scope was dodgy but testing with Logic oscillator it looks fine.
Then I noticed my original VCO and LFO were doing similar things and showing glitchy waveshapes. They were fine before.

I'm wondering if it might be a power draw problem.
I am using Ken Stones PSU design which recommends not going over 600mA.

The modules are:
2 x VCO
LFO
SYNTHACON VCF
ENVELOPE
VCA
MCV-876 MIDI to CV converter (Papareil Labs)

Not sure how much current this lot together might eat up.
Maybe it's another problem.
Any ideas anyone?
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Conboy



Joined: May 01, 2009
Posts: 25
Location: London

PostPosted: Tue Jun 16, 2009 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just put DVM across PSU. Measuring almost 500mA across the -15v to +15v rails.
More important, just noticed the transformer is rated for 250mA.... Confused I guess that's not good!
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fluxmonkey



Joined: Jun 24, 2005
Posts: 695
Location: cleve

PostPosted: Tue Jun 16, 2009 6:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

easy test: unplug the other modules and see if the VCO starts behaving...
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Sebo



Joined: Apr 27, 2007
Posts: 525
Location: Argentina

PostPosted: Tue Jun 16, 2009 7:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi:
Most Yusynth modules have a note in the schematic with the current drawing
for positive and negative rails.
The most current hungry module you have, should be the MIDI to CV, but all of them shouldn't
draw more than 200 or 250 mA.
Remember that current is measured in series with the load (disconnect the positive rail and insert the multimeter between the PSU and the distro board,
don't disconnect the negative rail neither the ground.
Usually the positive rail is the more current hungry.
Also take in account that leds draw current when are on, the VCA led for example,
don't light if you don't connect a signal to it. This could give a reading lower than a real situation one.
Your transformer is too small for that system anyway.

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Conboy



Joined: May 01, 2009
Posts: 25
Location: London

PostPosted: Wed Jun 17, 2009 2:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Fer sure it's too small!

Tried unplugging a few other modules and the new VCO is fine now.

Just ordered 50VA torodial from Farnell.

We live and learn. Wink
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yusynth



Joined: Nov 24, 2005
Posts: 1214
Location: France

PostPosted: Fri Jun 19, 2009 6:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Yep, if the current need is 500mA and your transfo 250mA only it is normal that the power supply cannot provide a good voltage to the modules.

By the way if you want to know how much your yusynth modules need I have created a spreadsheet :
excell spreadsheet
CSV spreadsheet

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