What lies under those outlet strip covers? The nice round stamped metal pinchy fingers for the neutral and live strips, and the lousy stamped flaps for the ground connections. Insert a ground pin a few times into these and the flaps spread apart in a mostly plastic (permanent) deformation. Eventually you get intermittent or no contact from those. I would not plug any equipment with safety-critical ground into an UPS or power strip using this type of ground strip.
Ground wires should be the same gauge as the feed wires to make reasonably certain they can safely carry whatever fault current the feed wires provide. Here, the cord is 3x16, but the ground wire linking the surge-only strip to the PCB and battery-powered strip is two gauges thinner at #18.
Another 15A breaker for a 13A cord. At this point, I am wondering if anybody is bothering to stock and use 13A breakers.
APC must be using this transformer in some other 550VA UPS variant with voltage regulation capability. Aside from the common battery terminal (bottom red wire) and the two inverter terminals (the loose black and white wires), the high voltage side also has three terminals, a telltale sign of the presence of a buck/boost tap that goes unused here.
This is one tiny and tightly packed PCB that does everything. Starting from the left, we have the micro-controller and its support components, the power supply, a bunch of analog support components, a few MOVs for surge suppression, a pair of Y-class capacitors and one X-class cap for EMI filtering, the battery power transfer relay, the pair of inverter driver FETs on tiny heat sinks, a pair of 30A fuses for the battery and the Ethernet surge protection.
The soldering quality looks fine overall and there are no components to be found on this side.
Network Surge Protection
Just like CyberPower, APC’s network surge protection is based on a bunch of 1N4007 diodes and a DIAC or similar device with a barely discernible ST logo on it. Unlike CyberPower, though, the double-sided board enables APC to use a much more compact layout.
Also unlike CyberPower's LX, APC did try to at least length-match the pairs between RJ45 jacks when they couldn’t be properly routed as differential pairs. In the bottom-left corner, you can see two solder triangles facing tip-to-tip. Instead of tying the network surge protection directly to ground or through some form of surge suppression device, APC chose to use an open-air spark gap. It's a little crude, but should get the job done since the whole point of a surge protector is to provide a lower impedance and lower breakdown voltage path to ground than the connected equipment. This gap should break at around 700V vs. the 2000V minimum Ethernet isolation requirement.
From the solder flux around the LED leads and the left tab of the USB connector shield, some rework was apparently necessary on this board.
More Spark Gaps
The network surge protection is not the only place where APC uses spark gaps. It employs three more for the USB interface as well.
I thought the blue marker treatment was mainly to check that through-hole components were correctly seated. But one capacitor and what appears to be one inductor in the USB interface circuitry are apparently critical enough to warrant their own squiggles of approval.
Primary capacitors for the AC-DC power supply are from OST. Most secondary-side capacitors are from Chang, except for one Jaimicon next to the optoisolator.
A bunch of components in this picture also have permanent pen squiggles. There must be a manual inspection checklist for those through-hole components.