It's an ex Smart-UPS 3000

[Billy-Bob]

I have a Smart UPS 3000 (SAU3000RMI2U) that has been out of use for a while, showing approximately 3v across for each battery in a re-commissioning check, therefore they were replaced.

After powering on, after about 30 to 40 seconds, there was a "sound of a small explosion" and the dreaded but expected smell of burning electronics.
I have always regarded APC as a top quality brand and am therefore a little disappointed.
The output devices on two of the heatsinks have vapourised. I have never heard of APCs failing like this and thought they were bulletproof.
Is this a known fault with this model or just an unlucky one-off?

edit for word duplication.

[Teken]

Based on the limited information provided here and personal experience. The unit had several existing problems which were bad capacitors and relays.

The capacitors were either dry, leaking, shorted. The relay(s) were probably welded together (stuck) closed. Power transistor’s on the output obviously exploded due to the sudden current passing through the system in an uncontrolled manner. ☝️

Both were shorted and thus the magic smoke was released! 🤦‍♂️

Questions Ask . . . 👍

[Billy-Bob]

Thank you
The original FETs are obsolete but have managed to find an alternative, I hope.
As the FETs have fried I suspect the driver is also dead or damaged.
Fortunately I have an oscilloscope and reasonable soldering skills.

On the down side, the relays look like nothing I have ever seen and I don't, yet, have a current limiting PSU to test the main board with the magnetics disconnected.
I supose a Variac or similar would be a useful tool too.

[Teken]

If this is simply a make work project vs must have for an Enterprise environment. It's highly suggested the unit be replaced as the operating service life is ten years. If however you're just Joe Average and want to try your hand on repairing this unit.

Replace all the capacitors, relays, power transistors . . .

Pay special attention to any diodes and inline SMT fuses as anytime there is a massive break down as seen in your unit. The down stream components are most definitely compromised / damaged.

Good luck and by all means circle back as to the final outcome! 👍