APC SMT 1000i smart ups blown capacitor value

[pval]

I wonder if someone has any idea about the value of the blown ceramic capacitor beside the 47K resistor. The photos are from the small PCB located on the rear of my APC SMT 1000i smart ups. The ups works but the pcb emits a terrible smell. One end of the 47K resistor has been desoldered, the other resistor is 51 ohm and both of them are ok. I searched but didn't find any schematics.

[floobydust]

Welcome to the forums

It's the snubber capacitor and I would wildly guess around 4.7nF at 500-1,000V rating.
But the PC board looks carbonized so you'd have to consider going through-hole to salvage it.

[asis]

Hi,

https://www.eevblog.com/forum/repair/apc-smt1500i-problem/

[pval]

Thank you

[Purduephotog]

Consider writing APC /Eaton about it. They ended up sending me an entirely new unit, although I did have a rather large fire in mine.

[RLP]

I've had 2-3 of these boards fail this way. That's a pretty bad case - I managed to shut mine down prior to them degrading to this point. What happens, I believe, is that the switching transformer itself starts to fail internally first - and then that is what causes the switching controller and its snubber circuit to overheat, damaging the components and burning the board as you see there.

You (or others having this issue) may be able to find replacement boards by searching the board number on eBay or similar. But make sure to get the correct version (120V or 230V - they both have the same part number but different components!). Otherwise, an option to salvage the rest of the UPS is to 'amputate' this board altogether and disable green mode as per this thread: https://www.eevblog.com/forum/repair/how-to-disable-green-mode-on-apc-smart-ups-smt-series/