API rack power supply

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raysolinski

Well-known member
Joined
Jun 16, 2004
Messages
329
Location
Cincinnati, OH
I am racking up 6 api 312 cards...3 with 2520's and 3 with Forssell's 992's...I have both power supplies built but my question is simple..can I power both supply boards (one at +/-16 for the 2520's, one at +/-24 for the 992's) with one 25-0-25V 1 amp torroid or will that be too much of a voltage drop for the +/-16 supply? I know the 317/337 regulators CAN do it but is it a good idea (heat!)? This thing will get beastly heavy if I have to stuff 2 power tranny's in there...

Cheers,
Ray
 
[quote author="raysolinski"]I am racking up 6 api 312 cards...3 with 2520's and 3 with Forssell's 992's...I have both power supplies built but my question is simple..can I power both supply boards (one at +/-16 for the 2520's, one at +/-24 for the 992's) with one 25-0-25V 1 amp torroid or will that be too much of a voltage drop for the +/-16 supply? I know the 317/337 regulators CAN do it but is it a good idea (heat!)? This thing will get beastly heavy if I have to stuff 2 power tranny's in there...

Cheers,
Ray[/quote]
I'd feed the +/-16V supply from the +/-24V supply as a preregulator, but feeding the 16V supply from the same source as the 24V part is ok too(YMMV). With a 50V center tapped transformer and allowing 10% line overvoltage, each 317/337 regulator would see about 38V raw DC at its input. From the datasheet, a 317/337 can stand a max.load current of 0.4A for a max.diff.i-o of 40V and up to 1.5A for a diff.i-o of <15V, that's even more than your 2x 0.5A transformer can deliver. Just use a bigger heatsink. (a 22-0-22V transformer would probably be enough for 10% line undervoltage and min. diff. i-o 3V for the regulator to get stable 24VDC)
 
Thanks Harpo..I have achieved +/-24 vdc from a 44vct transformer quite easily...I will slap a nice big heatsink on the 16 volt regulators and see how it goes..the opamps don't draw too much current so it should be okay load wise...

Cheers,
Ray
 
No need for the JLM since both supplies are already built..I am leary of bolting any regulators to the chassis....even with an insulator..I will stick with the 44vct and some big heatsinks and paste on the 16v regulators..

Cheers,
Ray
 
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