UPS Fault

Hi Everyone,

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, Michael

Reply to
Michael C
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So, you are worrying about a 40W load on a device designed for 1,000Watts? Try it with a 100W or 150W or 250W and see what happens.

(Yes, I know VA=/= watts).

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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 reseat it.

You will disconnect the batteries (as well as the mains) before you take the UPS apart, of course? !


Reply to
Sylvia Else





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.

Reply to

Thanks for the replies everyone, I will have another look at it in the next few days and see what I can find.

Cheers, Michael

Reply to
Michael C

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