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 Forum index » DIY Hardware and Software
Self heating ca3046 exponential converter
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debterminer



Joined: Feb 11, 2014
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PostPosted: Mon Jun 15, 2015 8:36 pm    Post subject: Self heating ca3046 exponential converter Reply with quote  Mark this post and the followings unread

Hello, im looking for any schematics or information relating to a exponential converter design i read about(which was at one point implemented in the moog prodigy) for a self heating ca3046 exponential converter.

What i have read is that the moog prodigy exponential converter used a single ca3046, and used one of the transistors on board the ca3046 to heat the chip instead of a tempco.

Im wondering if anyone has a schematic for this type of exponential converter design using the ca3046, or any information regarding this kind of design?
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Blue Hell
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PostPosted: Tue Jun 16, 2015 12:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

http://www.sinneb.net/?p=603

http://electronotes.netfirms.com/s019.pdf

http://mazmusic.free.fr/dllf/vintage/moog-service-manual.pdf

http://electro-music.com/wiki/pmwiki.php?n=Schematics.MoogTypeFilter

http://electro-music.com/forum/post-155122.html

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debterminer



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PostPosted: Tue Jun 16, 2015 6:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Jan what should I read to understand the article posted "http://electronotes.netfirms.com/s019.pdf" I do not grasp even its first paragraph :X
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elmegil



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PostPosted: Tue Jun 16, 2015 7:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Try

https://www.youtube.com/watch?v=ElUeQKrkfqc&list=PLXnFQqfHz_iFcdOTqI-6_FpOf73LWGNnt&index=7

and

https://www.youtube.com/watch?v=v9oaBudlzfc&list=PLXnFQqfHz_iFcdOTqI-6_FpOf73LWGNnt&index=8

None of which really addresses the "self heating" aspect, but might help get you there.
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debterminer



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PostPosted: Tue Jun 16, 2015 10:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you, i'll check those out. If anyones got any more relevant information i welcome it.[/i]
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Blue Hell
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PostPosted: Wed Jun 17, 2015 4:47 am    Post subject: Reply with quote  Mark this post and the followings unread

debterminer wrote:
Jan what should I read to understand the article posted "http://electronotes.netfirms.com/s019.pdf" I do not grasp even its first paragraph :X


Just skip that then and go to fig 6. on page 4 and the paragraph of text around that - where the heater / thermostat circuit is drawn out and explained.

You can then use two other transistors to make a standard expo converter.

Just keep in mind that the substrate of the transistor array should be at the most negative voltage in the circuit .. see the data sheet for that best. It is coupled to one of thee transistors and you could decide to not use that one.

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debterminer



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PostPosted: Wed Jun 17, 2015 9:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

thank you very much
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AndyR1960



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PostPosted: Wed Jun 17, 2015 9:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Take a look at the Dopefer VCO schematics - I've used the heater section to stabilize several Frequency Central System X VCOs with great results.

http://www.doepfer.de/a110_tec.htm

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debterminer



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PostPosted: Thu Jun 18, 2015 2:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

thank you andy
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forbin



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PostPosted: Fri Jun 26, 2015 6:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you use elements of the doepfer design dont forget the biasing on the extra transistor to the left (transistor on its own with two resistors). Jan also mentioned this earlier but it may not be apparent. Most of the common arrays have protection diodes and you need to make sure that the substrate pin is at the lowest potential of any of the other pins... Made that mistake in redrawing a moog 921b oscillator pcb... Sadness will ensue...
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debterminer



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PostPosted: Wed Jul 01, 2015 10:44 am    Post subject: Reply with quote  Mark this post and the followings unread

So im under the impression it should be at the supplys negative voltage rail?(-15v)
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wackelpeter



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PostPosted: Thu Jul 02, 2015 1:03 am    Post subject: Reply with quote  Mark this post and the followings unread

don't have to be -15V for each application i would say... maybe in your case it's right

have a look at Yves Usson's Moog or EMS filter... in one design it's directly to ground and in the other to -9V via resistor...

i guess that means the most negative potential you will have at this Array should or must be connected to pin 13 the substrate...

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Blue Hell
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PostPosted: Thu Jul 02, 2015 2:41 am    Post subject: Reply with quote  Mark this post and the followings unread

wackelpeter wrote:
i guess that means the most negative potential you will have at this Array should or must be connected to pin 13 the substrate...


Yes, that is the thing to do. There probably is some maximum voltage involved as well between any pin and thee substrate. The data sheet will, or should at least, mention that. Anyways, that might be a reason to not just connect it to -15V.

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