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- UPS Fault
- Michael C
July 19, 2009, 12:17 am
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I have a UPS which seems to have a component in it that is not stable. I
have a 40W light bulb hooked up to it and when I first turn on the ups the
light bulb brightness will jump around rapidly (when running on batteries).
If I switch to power then relays inside the unit start clicking in and out
approx 2 times a second and the brightness of the lightglobe jumps up and
down in incremements as the relays click. After the unit warms up the
problem completely dissappears. I could just use it but I'm worried if the
problem does appear when it is warmed up it might damage the computer or
even start a fire. Does anyone know what the likely culprit might be and how
I might test for it? I know the basics of electronics and what the basic
components do. The model is a Sola 325 1000VA
Thanks in advance for any replies,
Re: UPS Fault
I'm pretty sure the SOLA 325 models use basically the same circuit. My
comments below are based on my recent memory of repairing a SOLA 325 750.
When this UPS is running on the mains, its live output is a tap off its
transformer primary, which is being used as an auto-transformer. The
relays are just switching between taps.
When it's running off the battery, it's a simple inverter circuit.
What stands out as being common between the two is an LSI chip - there's
only one. I think I'd be inclined to remove it from its socket and
You will disconnect the batteries (as well as the mains) before you take
the UPS apart, of course? !
Re: UPS Fault
Some of these are "active" UPS, they will change taps (via relays) on
the internal transformer to compensate for rises / falls in the
incoming mains voltage, and will step up or down to try and maintain
the output power within sensible limits.
it is possible you have an abnormally low mains voltage and the thing
is cutting in and out of "UPS" mode.
The other problem (from you saying the light brightness jumps around)
it could be you have a bad connection to the battery, dry joints, bad
terminals etc, or dry joints on the PCB in the area around the
components that monitor the battery voltage and signal the processor.
If this is the case, the processor could do anything at all with
receiving this "bad info".
As the other poster mentioned, it might also need a minimum load.
Try that also, but beware that if there are dry joints or bad
connections around the battery supply terminals/tracks, something
could start burning and do damage with a greater load on it.
Observing the pcb for signs of stress or smoke when doing this (and
having one hand on the power button) might be a good idea.