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Author Topic: the cost of power (transformers)  (Read 2467 times)
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ssbothwell KJ6RSG
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« on: February 28, 2013, 03:25:36 PM »
hi guys. on my workbench i have a couple different power supplies, all of which have pretty low current ratings. i really wanted to put make a 30V/5A supply for testing amplifiers but i am struggling to find an appropriate sized transformer for cheap.

the only 36V/8A transformer i have found is a hammond one on digikey for $70 plus shipping. i dug through a pile of old transformers at my local electronics scrapyard ( http://www.apexelectronics.com ) but couldn't find anything with a high enough current rating and antek is 'out of stock' on sizes i would want. arrrgh.

sorry this post has no purpose. i have all the other parts (other then an enclosure) sitting in a box here and i really wish i could build a new supply.

i'm almost tempted to try winding my own transformer but i'm afraid of going down that rabbit hole.
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W2VW
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« Reply #1 on: February 28, 2013, 03:29:30 PM »
How about a 28 volt switcher? There are lots out there.
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ssbothwell KJ6RSG
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« Reply #2 on: February 28, 2013, 03:41:14 PM »
wont the switching frequency be a problem for linear amps?
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KU8L
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« Reply #3 on: February 28, 2013, 04:32:58 PM »
They are many EME guys running Max legal out of SS LARCAN ex-analog TV amp from 50V switchers that cost 35 bucks surplus.

THey work fine--the switching remnants that sneak thru to the secondary are easily filtered (actually easier than 60Hz with same size caps.)

FWIW

Curt
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ssbothwell KJ6RSG
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« Reply #4 on: February 28, 2013, 11:11:13 PM »
oh thats really interesting. i had been under the impression that linear supplies were essential for rf circuitry.

also, i totally forgot that that the rectified DC voltage is a result of the transformer's PkPk voltage (1.44 times the AC labelled voltage). i was looking around the scrapyard trying to find 30+ V transformers but i could have been looking for 20V-30V transformers as well. i guess i have to make another trip to the valey.  
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KA2DZT
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« Reply #5 on: March 01, 2013, 04:51:32 AM »
Look on ebay, you should be able to find xfmrs that would work.  There should be plenty of 24-28 volt xfmrs.  You may have use two xfmrs to get the voltage and amperage you want.

I just built in the last year a number of supplies in the 30-50 volt range.  I had the xfmrs.

Fred
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