User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 5th January 2004, 04:40 PM #1 diyAudio Member   Join Date: Jan 2004 Location: not nessesary About power supply Hi there i'm new in electronics and i dont find in books or in internet answer on my question.The question is:i bougth transformer 24-0-24 with 1.2 A rating ,putted 2x4700 uF capacitors and then checked the voltage on the output it was +/-31 volt ,and i quickly found the answer in the internet that it multiplies by about 40%.Ok but then i checked the Amper rating it was 9A i couldn't believe from 1.2A after capacitors 9A.In the internet everybody write that if i need to supply 50w amplifier i need 50w or more transformer but i bought another 15-0-15 transformer with 0.35A and after capacitors it could hold 50 w of output power.I couldn't belive that ,because it is like 0.35A*(22v+22v)=15.4W - it is transformer watt rating and it hold 50 w.Ok after that i checked the Amper rating after capacitors it was 3A icouldn't believe again so it mean 3A*(22v+22v)=132 W !!!!????????Can uyou explain me what rating is real transformer or after capacitors ,and if i use like 15-0-15 3A so will i get around 25 Amp after capacitors and will the microschem hold or blow after 25A......?
 5th January 2004, 05:13 PM #2 diyAudio Moderator Emeritus     Join Date: Jun 2002 Location: U.K. Measurement error You can only measure current (amps) by putting the ammeter in SERIES with the load.
 5th January 2004, 05:28 PM #3 diyAudio Member   Join Date: Feb 2003 Location: At home Hello! Isn't it possible to measure the voltage over a 1ohm resistor (added to the circuit) as the voltage = current? Cheers Tom
 5th January 2004, 05:45 PM #4 diyAudio Member     Join Date: Jun 2002 Location: Left Coast The problem with the current rating of a transformer is the same as the problem with the VA rating -- you can't measure it very well. The reason is that it is possible to draw quite a bit more than the rating from the secondaries -- until the transformer fails! The only way tio be totally sure is test to failure. It may be possible to get somewhat close by tracking the temperature, but that will be the external temperature and it is the internal one that is most closely tied to the failure point. As a practical matter you pretty much have to take the manufacturer's rating on faith. In any case, there is no simple way to put a meter on a transformer secondary and say "Ah, the VA rating is X."
diyAudio Member

Join Date: Jan 2004
Location: not nessesary
(here should be image amps.bmp)
SAFE OPERATING AREA it is tda1514a so if i use +/- 25 volt i would need to supply ~0.75A which transformer do i need?:+/-18v 0.75A or =/-18v and ~0.25 and can i use +/-18v and 2A??
P.S. help newbie how to post pics not by attachment?
Attached Images
 amps.png (1.5 KB, 31 views)

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post vectorplane Swap Meet 2 23rd April 2011 11:48 PM andy_c Software Tools 2 23rd August 2009 05:10 PM destroyer X Solid State 91 25th September 2006 04:36 AM ericpeters Swap Meet 0 14th January 2005 02:21 PM jarthel Tubes / Valves 10 21st July 2003 01:30 PM

 New To Site? Need Help?

All times are GMT. The time now is 09:50 PM.