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Date:	Sun, 9 Mar 2003 12:17:02 PST8
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-help@scoug.com
To:	scoug-help@scoug.com
Subject:	SCOUG-Help: Help with UPS...?

Content Type: text/plain

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Martin Rosenfeld wrote:
>
> I have a VOM.

Good. With the VOM you can trace the voltages on all three connections
(AC source, batteries, AC output). Be careful, of course.

WITH THE POWER OFF, you can measure the resistance between each
transistor's two connector pins and the case (the case is the third
connection). Measure in both directions (i.e. reverse the two VOM wires
and measure a second time). You may find that one or more of the
transistors are shorted. Also look at the board carefully and see if
anything looks burned or overheated (nicely roasted like an overcooked
chicken). Resistors sometimes overheat if something else goes wrong.
And sometimes there is a fuse on the board or somewhere inside the case,
so measure it and make sure it isn't open (don't just look at it, I've
had a couple "pop" inside the end cap so they looked good but were bad).

With power on, if the UPS doesn't work on either AC source or battery,
start at the AC output and work backwards. If the UPS works on one but
not the other, start at the one that doesn't work.

In particular, take a look for some large round metal transistors and
check their voltages (be careful not to accidentally short something
while you do this). They may be mounted on heat sinks.

If you have a schematic (as Steve Carter said) it will help.

- Peter

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