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 Forum index » DIY Hardware and Software » YuSynth
YUSYNTH VCO strange startup behavior
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gdavis



Joined: Feb 27, 2013
Posts: 126
Location: San Diego

PostPosted: Wed Oct 30, 2013 11:23 am    Post subject: Reply with quote  Mark this post and the followings unread

I've built several of these VCO's and they have 13.6V on the 78L15 and -14.2 on the 79L15.

Any problems I've had have been related to shorted or open traces.

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littlem4tt



Joined: Jun 30, 2013
Posts: 40
Location: uk

PostPosted: Wed Oct 30, 2013 11:56 am    Post subject: Reply with quote  Mark this post and the followings unread

great, thanks for that info! Very Happy
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littlem4tt



Joined: Jun 30, 2013
Posts: 40
Location: uk

PostPosted: Sat Nov 02, 2013 12:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

so i spent 3 days looking for errors on my pcb's, everything cheked out ok.
Then i decided to investigate the lm394 and found there were no transistors inside. So either i blew them up or i think i have some fake 394's. I have ordered a coupe more from different sources and this time i will measure them before i put them in.
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littlem4tt



Joined: Jun 30, 2013
Posts: 40
Location: uk

PostPosted: Tue Nov 05, 2013 5:46 am    Post subject: Reply with quote  Mark this post and the followings unread

So it seems i was sold some fake LM394's as i put in a fresh one from little diode (after measuring it with my Peak Atlas DCA inwich read each side of the ic
as NPN Darlington) and i was rewarded with a lovely lookin Sawtooth.

Now to calibrate!!!
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gdavis



Joined: Feb 27, 2013
Posts: 126
Location: San Diego

PostPosted: Tue Nov 05, 2013 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Reminds me of an old PC motherboard I had way back when the cache was on separate chips from the CPU. After upgrading the MB I took one of the cache chips apart and they were empty inside! Nothing but a plastic case holding metal pins. Pretty irritating.

In my digital logic lab in college we would pop TTL chips all the time. Pretty frustrating when you don't know if the problem is with your circuit or a bad IC. Sensitive little suckers.

I've only used discreet transistors in my VCO's but still wonder how much of a difference the 394's make. I can hear them drifting a bit when two are played together but I haven't epoxied them together with the tempco yet. Hopefully that will improve things a bit but maybe I should give the 394 a try.

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littlem4tt



Joined: Jun 30, 2013
Posts: 40
Location: uk

PostPosted: Sun Nov 24, 2013 12:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

I built 2 units both with lm394's and can say both are rock solid. I would like to know the expected current draw of this vco, it doesn't seem to say on the yusynth web site. Do you have a figure Yves?

Now I have calibrated all my oscillators ( 2x yusynth, 2x system X and 2x hearn morely) against the CV Standard module I can play all 6 oscillators with 1 cv line.......heaven!
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marfoski



Joined: Jan 26, 2011
Posts: 25
Location: Italy

PostPosted: Sun Nov 24, 2013 10:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Have a look at this post : http://electro-music.com/forum/topic-48470.html

According to Yves's spreadsheet, the VCO draws 27 mA from the positive rail and 28 mA from the negative rail.
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littlem4tt



Joined: Jun 30, 2013
Posts: 40
Location: uk

PostPosted: Tue Nov 26, 2013 4:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Awesome thanks for that. That 'is' the spreadsheet I was looking for!!
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