Altair-what do I do first

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Wed Sep 25 19:30:01 2002

Hi John
 Not all switcher are of the same high quality
as the ones you are testing. I've seen enough of them
that will turn the transistor on solid if the
the voltage is too low, in an attempt to bring the
output voltage up. This was more common in older
switchers than newer ones. Most are designed to
shut down, as John noted, now days. It wasn't
always that way.
 Even so, there is little useful results of using
a variac on these new ones. The only capacitor that
you are bringing up slowly is the primary side filter.
The DC outputs will snap to level when the input
protection allows it.
Dwight


>From: "J.C. Wren" <jcwren_at_jcwren.com>

> "( note: don't use a variac on a switcher supply! )"
>
> Why not? We do it all the time, for checking what the low and high
voltage
>cut-off point of a switcher is. We also vary the frequency all over the
>place. I don't know switchers in general, but ours suddenly start
switching
>as the voltage hits 90V on the up-test, and about the same on the
down-test.
>
> It may not be *useful* do to so for testing the device, but it won't
cause
>any damage in any of the number of supplies we've tested.
>
> --John
>
>
>-----Original Message-----
>From: cctalk-admin_at_classiccmp.org [mailto:cctalk-admin_at_classiccmp.org]On
>Behalf Of Dwight K. Elvey
>Sent: Wednesday, September 25, 2002 18:16
>To: cctalk_at_classiccmp.org
>Subject: RE: Altair-what do I do first
>
>[ snip]
>
>( note: don't use a variac on a switcher supply! )
>Later
>Dwight
>
>
>
>
Received on Wed Sep 25 2002 - 19:30:01 BST