Why does my UPS break AC adaptors?

Solution 1:

Have you replaced the power adapters and found that the devices still work? Have you bench tested the failed power adapters or tried them on other devices (assuming you have another device with the same plug and power requirements)?

If you mean that both the power adapters (i.e. “wall wart” or inline brick) for your router and external HD have gone bad while attached to your UPS, then maybe your UPS is the problem. I would find it abhorrent that a UPS would fail a way that would destroy a connected device's power conversion hardware, but I suppose it is possible.

It should be fine to power non-PC devices through a UPS. You would not want to run high-draw devices through a UPS (think Blendtec or KitchenAid), but a router and external HD should be fine (both should draw less power than a whole PC).