APC Back-UPS XS 1200 Always on Battery

[fuzzoli]

Hi EEVblog people!

I have a dead Back-UPS XS 1200 for which the "On Battery" light is always on.  From what I can gather from googling, this is a symptom of a bad MOSFET.  The only problem is, in the few posts mentioning the MOSFETs, nowhere do they indicate which MOSFET(s) are bad.  Since the UPS seems to work while "on battery", I assume the bad MOSFET is within the AC sense circuitry (I can't find any schematics).

Any thoughts?

Thanks,

-Frank
Holland, PA  USA

[PaulAm]

Try to find a schematic for that, most of them are floating around.  If you can't find the exact model look for something close.

I had a 350 that only ran on battery.  The charger switching IC had blown itself up.  Putting in a new IC and a couple of related caps brought it back to life.

Open it up and look for obvious failures.  Given the power these things handle many failures are fairly obvious.

[SoundTech-LG]

If anyone finds a stash of APC, or Tripp Lite schematics...   now THAT would be a find.

[PKTKS]

TRY HERE anything close

https://www.electronica-pt.com/esquema/conversores-no-break-ups-lcd-inverters/

PAUL

[ChuckDarwin]

Had several BX/RS? series.  Before pulling the soldering iron out, see if this is applicable: Try resetting the line sensitivity to low manually, then adjust if needed.  Unplug, re-plug, hold the power button in for 10-12 seconds till all the LEDs go active then tap the power button to set the sensitivity to low.  You can toggle through low/med/high and see 1, 2 or 3 LEDs light on the front of the unit.  Check the sequence in the docs if you have them, but I think that is correct.  I had several units that would randomly set the line sensitivity to high which drove them to battery on power-up (power->relay click->battery) and this was the standard fix with no management software involved.

This was the fix I came across for my last unit, now scrapped and glad of it:
Cap C41 and four of its friends for good measure.
https://www.tomshardware.com/reviews/apc-bx1000-ups-backup-psu-tear-down,4766.html

[SoundTech-LG]

Yep, that little collection of schematics is the motherlode, and the full extent of what you will find.
APC and Tripp Lite have it locked down really well.

[PKTKS]

Yep, that little collection of schematics is the motherlode, and the full extent of what you will find.
APC and Tripp Lite have it locked down really well.

there is a bit more here...
https://elektrotanya.com/?q=keres

and btw..  having no schematics is the certain method to have
unserviceable devices...

In due time bricks are just discarded.

usually replaced with some good serviceable unit.

and even WITH SCHEMAS - having no parts (or EXOTIC parts)
eventually lead to the same bricks...

2 cents of experience on that problem
hundreds of schemas collected even though ensures nothing

Paul