Question My UPS suddenly cuts all the power and do a long beep

[reikhard]

Hello, I have an recent issue after 8 years with my Mustek PowerMust 1000 UPS. It suddenly cuts the power for my PC after 30m - 1H plus of working - (my PC instantly shuts down) and the UPS does a reaaaally long beep (like beeeeeeeeeeeee-- and it won't shut up until I press the power button). (UPS malfunction)

It's weird because, when it is running, if I unplug it from the wall, it keeps my computer for the 10 mins that it's supposed to.

Batteries are OK, (I measured them, and made the UPS self test) Logs are empty (no time to register when shuts down). No software problem also.

I'm sure it's some hardware problem, electric transistor, capacitor etc... but can't figured it out yet .
As it is a online design UPS I suspect it is a problem in the inverter system, I've changed so far 2 voltage regulators, wich were in my opinion overheating and could shutdown.
I will replace all the power mosfets and some capacitors also...

Anyone with same problem or ideas, that could help me out? Thanks

 

[COLGeek]

Are the batteries the original 8 y/o ones that came with the UPS? If so, they are the likely issue, in spite of the test results.

 

[Ralston18]

In agreement - likely the battery.

And there is a meaning to the "long beep":

https://www.manualslib.com/manual/920799/Mustek-Powermust-400-Offline.html?page=9#manual

Note: Manual covers the 400, 600, and 1000 models.

Check the Indicator lights/LEDs also.

 

[reikhard]

Thank You Guys for your replies, I've replaced the batteries 3-4 years ago and I remember the malfunction was nothing like this, each battery is around 13V so they are balanced and at optimal voltage, also I've performed the UPS self test and even left the UPS drain all the power from them till it automatically self shut down my PC. Everything was normal.

 

[COLGeek]

Thank You Guys for your replies, I've replaced the batteries 3-4 years ago and I remember the malfunction was nothing like this, each battery is around 13V so they are balanced and at optimal voltage, also I've performed the UPS self test and even left the UPS drain all the power from them till it automatically self shut down my PC. Everything was normal.

It may just be time for a new UPS.

 

[reikhard]

It may just be time for a new UPS.

I'll try to fix it as I mention above, (way more cheaper than a new one) but it will take some time to get all the parts and to proper test it.
Anyway no matter what happens I'll try to leave some feedback later.

 

[COLGeek]

Good luck.