On Thu, 17 Feb 2011 07:22:57 -0800 (PST), jamesgangnc
wrote:

On Feb 17, 10:14Â*am, Tegger wrote:
Art Todesco wrote in news:ijj941$bqu$1
@speranza.aioe.org:

I have a computer and DSL modem tied to an old UPS (with new
batteries). Â*When I have a power failure, the computer keeps right
on ticking, but I always have to restart the DSL modem. Â*I've even
restarted the modem while running on the UPS and after its restart,
all was fine. Â*I am assuming here that the switch over time is
killing the modem. Â*I looked at the modem and its walwart. Â*It says
12 VDC. Â*I was wondering if putting a few thousand micro farad cap
across the 12 volt line might help. Â*Anyone have any experience with
something like this?

The UPS is probably switching in too slowly for the modem's logic
circuitry.

The need to restart the modem is a giveaway that it's losing power for the
tiniest moment, just enough for its logic to /begin/ to die, but not enough
for it to die /all the way/ and thus do a complete reset on the new power-
up.

I think you need a newer UPS.

--
Tegger

The cap if it works would be a whole lot cheaper solution. I'm not
familiar with smaller ups' only the big ones. I assume the smaller
ones keep costs and heat down by not running the power through a power
supply and inverter 100% of the time. Thus they have to switch
sources.
Even a lot of the "larger" UPS units work that way. There are
"standby" units (the cheap kind with switch-over drop-out), Line
interactive (which switch over very quickly, using zero crossing
switches or similar tech) and there are the genuine on-line, or "dual
conversion" units the have absolutely no change-over or drop-out - and
you pay accordingly.