We have a Dyson DC25. For a big apartment/ flat, you might want a DC40 or DC41 or a Big Ball. it is a light, flexible design, and bagless is very convenient. In a recent thread about someone moving to a new house, several other people recommended Dyson. In tests, Henry, as recommended by several people, often scores highest for suction. Office cleaners and builders often use Henry. Try to find one of the options here. If you go to a big Currys, they usually have a test area for vacuums. You can try various ones out....
If you actually need to do the board level work, this would fit better into Level 3, but before that.... Take it to an independent shop and see what they say. Preferably mention apple said it was a board failure and many of us shops will take that as a challenge/chance to show that Apple is full of it (and at least my store will do a no fix/no recovery no fee for this type of showing off) Apple's "diagnostic" usually consists of plugging it into their diagnostic machine and if it gets no response it calls the whole unit dead. That could be as simple as a clogged charge port with lint, or as complicated as the processor actually failing and about a million things in between.
As someone else said, you need to verify 12v at you constant and accessory wire. So you should verify ground. Fake a little bit so you can not quote me on that.
