Re: Cheap/generic PSUs - any good? (was: Low power socket A)

From: Mike (mjb_at_posie.local.dom)
Date: 09/26/04 

Date: Sun, 26 Sep 2004 15:36:35 +0000 (UTC)

In article <10l19fpsc3h0p2d@corp.supernews.com>,
David Maynard <dNOTmayn@ev1.net> wrote:
>Without a load the PSU can't regulate (an inherent characteristic of
>switching power supplies) but, while I can't say I've seen 'every' power
>supply out there, I've never seen one 'burn up' from being unloaded.

Just the one: Supplied in error in place of the model that should have
been sent. The ordered model had no minimum current (internal ballast
resistors). The supplied model ... didn't.

Switch on ... tick tick tick stop ....

Died taking out numerous components. Returned for replacement.

This was not a PC supply though, just a generic Switch Mode.

>The other is over-voltage protection (OVP). That circuit should clamp the
>output to a 'safe' level if something in the PSU fails causing it to put
>out excessive voltage. That would only matter if the fault specifically
>caused an over-voltage rather than, say, the outputs going dead to begin
>with. It's effectiveness is complicated by how fast it responds and how it
>controls the voltage.

I think this was the cause of the failure. No current drawn, no ability
to sense output voltage. Voltage rises in an attempt to hit nominal
voltage, and (unfortunately) overshoots it. Protection kicks in and
clamps power supply output. Repeat until failure. 

-- 
--------------------------------------+------------------------------------
Mike Brown: mjb[at]pootle.demon.co.uk | http://www.pootle.demon.co.uk/

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