electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
CGS14 PSU
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [7 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
Dave Kendall



Joined: May 26, 2007
Posts: 413
Location: England
Audio files: 3

PostPosted: Tue Jun 17, 2008 2:20 pm    Post subject: CGS14 PSU
Subject description: Cap sizes and values 'an ting......
Reply with quote  Mark this post and the followings unread

Hi all.

Am building PSUs right now, one of which is
this one . What effect has increasing the cap from 2200uF to 3300uF on the circuit if using a CT 18 - 0 - 18 AC transformer?

Also what is the danger (if any) in using 25V rated electros?
I've got a fair few of these, but not many 35V jobbies.

Cheers,
Dave

"Help me Electro Forum Kenobi - you're my only hope" Smile
Back to top
View user's profile Send private message
andrewF



Joined: Dec 29, 2006
Posts: 1174
Location: australia
Audio files: 4

PostPosted: Wed Jun 18, 2008 1:28 am    Post subject: Reply with quote  Mark this post and the followings unread

There is an equation flying around somewhere to help you work out the best size caps for a circuit like this. Maybe it's in Art of Electronics?
Anyway it won't make a HUGE difference using 2200 or 3300, though 3300 will help smooth out the higher voltage and make life easier for the regulators.

Best just to try it and see, if you can hear a 50/60HZ hum through your modules, or general noise, try bigger caps.

but the voltage factor. I recently had a mishap that blew out a positive regulator and resulted in about 60VAC going thru a dozen modules - lots of dead cmos! My caps were all 50V and 100V and survived.
Anyway, if you use 25V rated caps with an 18-0-18 transformer, they won't be happy if something goes wrong. They kind of burp and this greasy smoke comes out.

Best to build your power supply well and strong, it is the heart of the synth.
Back to top
View user's profile Send private message Visit poster's website
otherunicorn



Joined: May 11, 2008
Posts: 136
Location: Australia

PostPosted: Fri Jun 20, 2008 10:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

With an 18-0-18 transformer, the recified voltage will be very close to or even a little over 25 volts. If the transformer puts out an over voltage (and they all do under minimal load) you will be wiping electrolyte from you equipment after they explode.
As for the 2200/3300 question, it really depends on your load. If your rated transformer current capacity x 0.7 is near what current you will be pulling from the supply, you are going to need the bigger caps, because you are at the limit of the transformer, resulting in a lower peak voltage, and thus less operational headroom for the rectifiers.

_________________
http://www.cgs.synth.net/
Back to top
View user's profile Send private message Visit poster's website
Dave Kendall



Joined: May 26, 2007
Posts: 413
Location: England
Audio files: 3

PostPosted: Sat Jun 21, 2008 3:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi guys.

Thanks for the concise replies. Smile
I have some 18-0-18 transformers rated at 75VA - but am getting nowhere trying to work out how much current that equates to in this circuit. The stuff I've read so far is a bit over my head I'm afraid, or I'm just not getting it.....

Is there a simple way to work this out for this circuit and the CGS66?

Thanks.

cheers,
Dave
Back to top
View user's profile Send private message
otherunicorn



Joined: May 11, 2008
Posts: 136
Location: Australia

PostPosted: Sat Jun 21, 2008 4:42 am    Post subject: Reply with quote  Mark this post and the followings unread

It can supply roughly 1.4 amps at the output of the supply. Of course this is more than the CGS14 or CGS66 can deliver, but both gould be rund from this one transforem with no problems.
For the sake of this discussion, 75VA / 36V = 2.08 amps. Rectification will convert that to roughly 50V across the outer rails with 1.4 amps available.
The voltages will vary with load due to reality getting in the way Smile

_________________
http://www.cgs.synth.net/
Back to top
View user's profile Send private message Visit poster's website
Dave Kendall



Joined: May 26, 2007
Posts: 413
Location: England
Audio files: 3

PostPosted: Sat Jun 21, 2008 5:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Ken.

I'll try and run the CGS14 and an EFM 3501 (similar to the CGS 66) from the same 75VA transformer - as they're what I've got right now)
I'll have to fing a way of cramming 3300 or 4700uf caps on the EFM board - perhaps chassis mount....... If I can't get that to work, I guess I'll be after a couple of CGS66s Wink
I guess the secondary AC outputs are simply paralleled to the normal ± and 0V inputs of the PSU boards....
Fuses before both sets of inputs would seem like a good idea too....

Many thanks for the help. Smile

cheers,
Dave


3501.pdf
 Description:

Download
 Filename:  3501.pdf
 Filesize:  432.15 KB
 Downloaded:  180 Time(s)

Back to top
View user's profile Send private message
Dave Kendall



Joined: May 26, 2007
Posts: 413
Location: England
Audio files: 3

PostPosted: Wed Jul 16, 2008 3:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi.

Ken wrote
Quote:
t can supply roughly 1.4 amps at the output of the supply. Of course this is more than the CGS14 or CGS66 can deliver, but both could be run from this one transformer with no problems


PS - it's a 18-0-18 75VA AC transformer.

On another thread, and on JH's site, JH has explained that AC from a 18-0-18 transformer can't be sent to the power inputs of two of his boards simultaneously (the Tau and the triple chorus). The power input/regulator sections of those boards look similar to the CGS 66, except for smaller smoothing caps and lack of heatsinks. Can anyone explain the difference, and why running AC to 2 boards simultaneously would work with the CGS PSUs and not the JH boards?

Sorry if this is a weird question, but it's got me stumped, and and I want to learn as much as possible about PSUs and wiring before actually connecting a transformer to the mains.

The other thread here on the 1A PSU started by Fonik has been very useful indeed, but I still don't get the question above........

Any thoughts or explanations will be very welcome. Smile

cheers,
Dave

(edited to change CGS14 to CGS66 in 3rd paragraph and make things clearer)
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [7 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use