On Feb 19, 8:43*pm, Sylvia Else wrote:
On 20/02/2011 7:56 AM, martinmarty wrote:





I have a UPS about 11 years old. It is an IBM OfficePro 700 which is
actually a Tripp-Lite product. Inside on the circuit board it says
66-0546. The web says the Mfr model number is 10K1912.

Not too long ago its yellow light started flashing that says the
batteries are discharged. Because of its age, I assumed the batteries
were worn out so I bought new ones. Unfortunately, after installing
them the problem did not go away.

When plugged in to AC, the unit has its green LED lit which shows it
is getting AC power in. The yellow LED flashes. according to the
manual, "This yellow light will turn ON continuously to indicate that
the UPS's battery is less than fully charged. If it stays on
continuously, contact Tripp-Lite fo service. The light will flash
after you set the 'OFF/ON' Switch to the 'OFF' position to indicate
that the UPS will not provide battery backup during a blackout or
brownout." Regardless of whether I set the OFF/ON switch to OFF or ON,
the yellow light flashes.

There is a Mute/Test switch. If I run the test, the red LED briefly
lights and the alram briefly sounds, as if it tried to switch over to
battery power but there was no power there.

It kind of seems like the charging circuit is not charging the
batteries but I don't know how to test this theory. I left it sit
plugged in for a few days hoping it would charge but it did not.

There are several fuses on the circuit board, all soldered on, and
they all measure zero ohms so I don't think that is the problem. There
are no obviously leaky capacitors or any other components that look
burned up or damaged judging by visual inspection.

I like this UPS and would like to revive it, especially since I spent
money on the new batteries. If anybody could help me diagnose the
problem, tell me where to start, what to check, etc. I would
appreciate it.

All ideas welcome. Thanks in advance.

*From your description it appears that the light is flashing, whereas if
the UPS considered the batteries insufficiently charged, the light would
be constantly on.

I'd check the continuity and connections to the on/off switch, given
that your manual effectively says that the flashing light means that the
switch is in the off position. Make sure the switch continuity actually
changes state, and determine whether it's closed in the "on" position,
or vice-versa (the latter seems unlikely, but best not to assume). Try
to track the connections from that switch back to whatever is looking at
it - probably an IC - could just be a dry joint, or a short, depending
on how the switch is used. If you can track back to an IC pin, you can
check whether it changes state - with suitable care given that you'll
need the battery connected, and this device might start generating mains
voltages at any moment.

Sylvia.- Hide quoted text -

- Show quoted text -

THANKS, Sylvia, and thanks to each of you who took the time to try to
help me.

Good call on the flashing light = unit off = bad switch. Problem
solved.

It looks like a typical SPDT slide switch. As I was preparing a state
table of the switch leads to show you all, I thought how unusual it
was that the continuity toggled normally between the "left" and center
poles when the switch was moved, but between the "right" and center
poles it was always open. So I started monkeying around with the
switch and sure enough, at one point I got it just right and got
continuity between the "right" and center. I hooked everything up and
got a green AC indicator with no flashing yellow, just like we wanted.
I plugged in a small load and killed the input power and voila,
battery backup!

I flipped the switch back and forth a bunch of times and now it
actually seems to be working pretty consistently, so at least for the
time being I'm not even going to replace it. If it screws up again it
will be first on the hit list.

I'm glad it turned out to be the switch because the way the board and
components are laid out, I was getting nowhere on tracking the
connections from the switch.

This solved two problems for me:

1) The dead UPS.

2) The dead UPS has been in pieces on my kitchen table since October
and I have parts for a new PC hopefully coming tomorrow, so I needed
to make room for that project.

THANKS AGAIN,
-Marty