Got an HP AIO in the other day with no signs of life. No power or lights. Disassemble was tedious due to bad design. Basically needed to free 4 more screws holding the shield down and was not able to access those due to the plastic mid-frame, so 20+ screws later, we got to the board.
First I checked for power in, 12.86V. Got that from the power supply cables, but noticed the in-series mosfets were being dropped from 12.86V > 0.2V, for some unknown reason. Removed the board to check for shorts, no obvious shorts on the power rails and larger caps. So, next step was to check readings using the bench power supply.
Setup bench supply with appropriate voltage and saw that it was taking a small amount of current. From here, went straight to voltage injection (1V/3A). Injected voltage after the dual mosfets and noticed a protection diode heating up. I somehow missed this area when probing with the multimeter, near several large tantalum caps. The diode was doing its job and shorting to ground as there was a short on the main power rail.
This led us to inject voltage after the diode and finding the shorted cap right next to the cap I was injecting on. Busted out the soldering iron and worked in the tight area to remove the shorted cap. Confirmed short after removing from board and did notice physical damage underneath the smd component, something like a small crack. Confirmed short was gone and that charger voltage was making it through the dual mosfets. Next, was a bit of reassembly, basically putting it mostly back together just to test as there was no other way.
Thankfully, it powered on after the initial cmos reset, with fans spinning and finally something on screen. Unfortunately got stuck on a bitlocker warning screen, and is kind of why I despise bitlocker for home users. Worst case with bitlocker is data loss, so why run the risk? Thankfully we were able to recover the Bitlocker key from the linked Microsoft account, and I was able to finish testing the system. Customer was happy and had a working computer and their data back. Could have turned out worse, with an expensive board replacement upwards of $500, but all in all, am glad to have helped this customer.