Electronics > Repair

Magic Smoke from a 1U Backup UPS (Trippelite Smart1500)

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kml183:
Hello!

I bought a used smart1500 backup ups for my server rack on facebook marketplace. Before I purchased it, I double-checked that It would boot up and that the battery was detected. When I got back to my place, I took it apart and noticed that some magic smoke was definitely released around the transistors that are used in the inversion circuitry from 12VDC to 120VAC. Also C25 on PCB was so hot it desoldered. See the attached images  :-BROKE :palm:. I can see a little hole on one of the transistors attached to the heat sink. Is it reasonable to fix something like this so that I could actually rely on it? I would like to leave it on while I travel.

Thanks

fmashockie:
I can't really tell from your photos which components you are referring to.  Are you saying you left it on when you went away, and then came back and the unit had failed? I'm not too familiar with this make/model, though Tripp-Lite generally makes quality surge protectors.  If you are able to fully resolve the issue with this unit, and thoroughly test it, there's no reason why you shouldn't be able to rely on it.  I would also test the batteries.  If you don't have the ability to thoroughly test them, and they came with the unit you bought used, it would be a good practice just to buy new ones for it.  Bad batteries are what reeks the most havoc on UPSs. 

kml183:
I have not seen the unit fail. I have plugged it in and it seems to work.

The burnt components are the transistors that are connected to the aluminum heat sinks.

fmashockie:
I can't really see that they are burnt from you photos.  If they were damaged, the unit would not work.  As you stated, they are part of the inverter circuit.  Your unit would not be able to go into backup battery mode without these.  It would likely trigger an error as well if they were shorted.  These units typically have the ability to sense internal shorts.  But if you can clearly see they look burnt, I would suggest replacing them.  These MOSFETs can take a lot of abuse over time.  They handle large amounts of current which is why they are adhered to such large heatsinks.  But as I said, as long as you've resolved this potential issue, and gave the PCB a thorough inspection (replacing other potentially out of spec components like electrolytic caps) there's no reason why you shouldn't be able to rely on this for daily use.  That being said, this is a more general statement.  I am not too familiar with Tripp-Lite's UPSs.  Do some research on this model.  If there's a known failure mechanism (like I've ecountered with some APC UPS brands), then maybe switch to a different product.
 

kml183:

--- Quote from: fmashockie on September 01, 2023, 03:28:12 pm ---I can't really see that they are burnt from you photos.  If they were damaged, the unit would not work.

--- End quote ---

My mistake, I meant that the power distribution feature works, I never tried the battery. I took it apart further with the intention of fixing it. I definitely don't think I will be doing that now  :-//

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