test bench variable psu

reapersdirge · 13th December 2012, 05:58 AM

hi all...
im trying to figure out what im looking for so please bear with me. im after a mains to variable psu. ideally id like to be able to test various components and builds troubleshoot with various voltages preferably from 0-240v. does anyone have any thoughts on these does such a device even exist?

reapersdirge · 13th December 2012, 06:10 AM

ah found what i was after sifting the forums. a variac.
can anyone recommend a spec?
first off id like to test a power amp i made. it has two torods one at 625va the other at 500va

merlin el mago · 13th December 2012, 07:38 AM

The sum is 1125VA, to be in the safe side I will buy 1500VA.

Enzo · 13th December 2012, 07:43 AM

You can play it safe and get a huge variac that can handle the full current of your units under test. However in my experience, at least in troubleshooting, the main value of a variac is to bring something up slowly while watching for excess current draw. That level testing is never done at full power draw, at least not in my shop. Once an amp is proven to be stable, then I bypass the variac and connect direct to the mains for full power tests. SO I have a small variac beside me with an 8 amp mains fuse (at 120v mains, I suppose a 4 amp for you at 240) that is sufficient to power up even 2400 watt amplifiers.

Once I know an amp will sit there idling peacefully, and then producing a small amount of watts sinto a load, then I take it off the variac. I can't imagine running 2400 watts out of an amp into load and dialing the mains down while that was going on. A lab might need that capability, but not a general audio shop like mine.

Your 625VA toroids may be able to put out that much power, but they don;t draw that much just sitting there.

I haven;t mentioned a specific spec, because I'd be looking at what I could find and decide if it would meet my needs. I might arbitrarily decide I want a 10A variac, but then I see this 8A unit available cheap locally, and off I go to get it. I have a collection of variacs from small 3A types up to some very large ones, but the 8A unit seems to cover me and not take up the whole bench. Translate those numbers into your 240v world.

Just my opinion, others may disagree.

freax · 08:01 AM

I would hate to see what will happen once an intermittent blackout occurs to this amp that you've made and to the power socket!!!

What size are the filtering capacitors on your amplifier? Matter of fact whats the rest of the amplifier like?

reapersdirge · 13th December 2012, 08:05 AM

are you querying the filtering caps on the inrush limiters by chance?

13th December 2012, 05:58 AM	#1
reapersdirge diyAudio Member Join Date: May 2012	test bench variable psu hi all... im trying to figure out what im looking for so please bear with me. im after a mains to variable psu. ideally id like to be able to test various components and builds troubleshoot with various voltages preferably from 0-240v. does anyone have any thoughts on these does such a device even exist?

13th December 2012, 07:52 AM	#5
freax Owner and operator of irc.tenettenba.info diyAudio Member Join Date: Sep 2007 Location: NSW	I would hate to see what will happen once an intermittent blackout occurs to this amp that you've made and to the power socket!!! What size are the filtering capacitors on your amplifier? Matter of fact whats the rest of the amplifier like? __________________ Last edited by freax; 13th December 2012 at 08:01 AM.

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13th December 2012, 06:10 AM	#2
reapersdirge diyAudio Member Join Date: May 2012	ah found what i was after sifting the forums. a variac. can anyone recommend a spec? first off id like to test a power amp i made. it has two torods one at 625va the other at 500va

13th December 2012, 07:38 AM	#3
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	The sum is 1125VA, to be in the safe side I will buy 1500VA.

13th December 2012, 07:43 AM	#4
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	You can play it safe and get a huge variac that can handle the full current of your units under test. However in my experience, at least in troubleshooting, the main value of a variac is to bring something up slowly while watching for excess current draw. That level testing is never done at full power draw, at least not in my shop. Once an amp is proven to be stable, then I bypass the variac and connect direct to the mains for full power tests. SO I have a small variac beside me with an 8 amp mains fuse (at 120v mains, I suppose a 4 amp for you at 240) that is sufficient to power up even 2400 watt amplifiers. Once I know an amp will sit there idling peacefully, and then producing a small amount of watts sinto a load, then I take it off the variac. I can't imagine running 2400 watts out of an amp into load and dialing the mains down while that was going on. A lab might need that capability, but not a general audio shop like mine. Your 625VA toroids may be able to put out that much power, but they don;t draw that much just sitting there. I haven;t mentioned a specific spec, because I'd be looking at what I could find and decide if it would meet my needs. I might arbitrarily decide I want a 10A variac, but then I see this 8A unit available cheap locally, and off I go to get it. I have a collection of variacs from small 3A types up to some very large ones, but the 8A unit seems to cover me and not take up the whole bench. Translate those numbers into your 240v world. Just my opinion, others may disagree.

13th December 2012, 08:05 AM	#6
reapersdirge diyAudio Member Join Date: May 2012	are you querying the filtering caps on the inrush limiters by chance?