I’ve an UPS but it’s not working fine. Disassembled it a bit and tested components that I could without unsoldering, everything seems good. Then the problem is :
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Normally I should be able to connect the batteries and the UPS would just be in “sleep” mode, the screen would be fully light up but the UPS should be off
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The problem here is that firstly when I plug batteries the fan turns on, it should not and only turned on when on batteries but when the UPS is on
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The second problem is that the screen doesn’t work as intended. This is a screen that has prewritten zone that just have to be lighted up (don’t know the name of this kind of screens, the type like in digital clock), here only the backlight is lighted up (normally all the possible drawing are lighted up too), but quickly it begins to drop in lightness to turn black at the end (the fan continues running)
Check the batteries they are 2 x 12V at 12.6V here
Thanks for your answer
EDIT : on the photo the two blue and brown cable at right are the power plant electricity going to the UPS
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Those big mechanical relays will wear out , test them to see if they still click when applying the low voltage.
Gonna try it
- Has it at anytime worked like you describe?
- If it stopped working, what happened?
- What have you tested, how, and with what results?
12.6V is low if it’s 12V lead acid. Could be that the UPS is just charging the batteries and attempts cooling them meanwhile.
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Almost there is definitely a problem. It was working fine, but sometimes it would just not go to batteries and stuck in a fault with continuous beep. After that, I let it for 2 weeks, the batteries were 5V, but I tried to charge them and for now they went to 12.6V stable (as normal…), but even with that it does the problem described and does not works as before
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Answered in the 1.
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I’ve tested the resistors, all proper to their written value, and relays, proper resistance too (85 ohms for one (just on the brown power plant cable), and 260 for the others)
Will try to find others batteries to try, but normally it charges batteries by lighting up the display properly + the fan does not start. And here the UPS is not connect to any AC power, only the batteries were plugged
- Almost there is definitely a problem. It was working fine, but sometimes it would just not go to batteries and stuck in a fault with continuous beep. After that, I let it for 2 weeks, the batteries were 5V, but I tried to charge them and for now they went to 12.6V stable (as normal…), but even with that it does the problem described and does not works as before
That does sound like some part of the controller electronics has been dieing for a while, and has now finally keeled over.
- I’ve tested the resistors, all proper to their written value, and relays, proper resistance too (85 ohms for one (just on the brown power plant cable), and 260 for the others)
You wrote originally, that you tested what you could with desoldering anything. Measuring resistance in circuit always renders a murky result.
The brown wire is likely what is known as phase or live. Blue will be neutral. But measuring resistance on the input only tells you how much current will flow in the present state of relays.
What could help you come closer to an answer is following the first law of troubleshooting “thou shalt check voltages”. With a device that operates two live rails this will not be both easy and safe at the same time, so don’t rush it. I suggest you figure out what voltages to measure, then solder wires to the relevant nodes. Terminate the wires in a terminal block, where you’re protected from touching the screw. Assemble the device as best you can with all the wires coming out, and then power it on, get your voltages and deduce from that.
Whatever you do, do not poke about a live UPS circuit with your multimeter probes directly.
My initial working theory would be that the transistor switching the fan is dead and I would be looking closely in that area. If that transistor has failed closed and is shorting the controller electronics VCC rail, that would explain a lot. Maybe I’d go so far as to test it without checking voltages (gasp!)
If you just desoldered the transistor and powered the UPS back on, that could give you a UPS with functioning display and an idea of what to replace.
Will try to find others batteries to try, but normally it charges batteries by lighting up the display properly + the fan does not start. And here the UPS is not connect to any AC power, only the batteries were plugged
If 12.6V is normal for your batteries, then there’s no reason to troubleshoot that route any further. 12.6 is little low for lead acid, but if it’s a different chemistry. Anyway keeping extra batteries is always a good idea.
That does sound like some part of the controller electronics has been dieing for a while, and has now finally keeled over.
Will try to check the transistor and else
You wrote originally, that you tested what you could with desoldering anything. Measuring resistance in circuit always renders a murky result.
Okay didn’t really known that, not so good in electricity sadly… :(
The brown wire is likely what is known as phase or live. Blue will be neutral. But measuring resistance on the input only tells you how much current will flow in the present state of relays. What could help you come closer to an answer is following the first law of troubleshooting “thou shalt check voltages”. With a device that operates two live rails this will not be both easy and safe at the same time, so don’t rush it. I suggest you figure out what voltages to measure, then solder wires to the relevant nodes. Terminate the wires in a terminal block, where you’re protected from touching the screw. Assemble the device as best you can with all the wires coming out, and then power it on, get your voltages and deduce from that.
Didn’t really understand, can you explain it a bit more? Sorry 😅 About your warning is it dangerous to measure a 230V current with my multimeter (with precautions, gloves mainly)
My initial working theory would be that the transistor switching the fan is dead and I would be looking closely in that area. If that transistor has failed closed and is shorting the controller electronics VCC rail, that would explain a lot. Maybe I’d go so far as to test it without checking voltages (gasp!)
Going to check that, but what are the VCC rails?
About the batteries, I didn’t think they are fully charged with their 12.6V, and I should try to make them go around 12.8-12.9V, but is it possible that because they have gone to 5V they wouldn’t have enough “punch” now and wouldn’t be able to work properly?
Didn’t really understand, can you explain it a bit more? Sorry 😅 About your warning is it dangerous to measure a 230V current with my multimeter (with precautions, gloves mainly)
Depending on the meter and your approach it can be either safe or lethal. The more I think about it, the more I’d recommend that you just don’t do it at all. Working on 240V installations under voltage, that is something we teach electricians to do safely. Besides the training it involves some special and rather pricey equipment.
I cannot stress this enough, if you mess up, you will hurt yourself with enough severity that the can easily be fatal. If you don’t know what you’re doing, messing up will be exponentially more likely.
Desolder the transistor, does the rest of the board light up? If so replace the transistor. Otherwise, get trained assistance on person or replace the UPS. I’m all for learning electronics, but not on a live UPS.
Thx for the advice, gonna check the transistor
And I think that my meter is capable of 240V but gonna inspect it with help of electricity guy
It’s not a matter of whether your meter can do 240V, can you do 240V? Because that can be the consequence of slipping with the probe.
Sorry, I don’t mean to come off all aggressive. I just want to make sure that you don’t hurt yourself because I wasn’t very clear in my communication.
Ohh okay don’t worry for being too “aggressive”
Thank you for saying out the risks for people like me who doesn’t know that much in electricity
And thank you for your answers
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Make and model of your ups please
Its a Riello UPS NPW 2000
If the fans are running at full blast, maybe you accidentally disconnected a temperature sensor?
I don’t think there is any temperature sensor because the fan is simply turning on when on battery. Update the post with a picture of the pcb