If you haven't already, though I suspect you probably have, disconnect everything from the motherboard unnecessary to boot from the motherboard, including the LCD, keyboard, wireless card, etc. You just want the power button, battery, and one stick of memory. Try turning it on with an external monitor attached if possible (if not, keep the LEDs connected). See if it behaves the same way. If it works now, reattach things one piece at a time till it's working. Shorted components can cause weird behaviour like this. You could also try to re-flash the BIOS. First you'll need to find it - look for a memory chip, usually in a SOIC8 package, and it's usually somewhere near the CMOS battery connections. Buy yourself a buspirate if you don't have one and and use flashrom to write the bios file onto the chip.

There are 2 versions of the touch screen for this model. I'm willing to bet that you have the wrong one. That's the only thing that I'm aware of that can cause this.

I'm assuming you've waited for a while - sometimes they won't respond for a 30-60seconds or so after booting. If so, the digitizer is not working on the display. It could be a faulty display, but often it's just that it got disconnected. Follow these instructions steps 1-15. Notice the last thing you disconnected was the digitizer. Check the cables and connectors for dirt or pieces of glass or similar that could sit inside and keep the connector from fully seating - clean it out with air and/or alcohol swabs. Then click the cables back on the connectors in the reverse order of steps 13-15. You can now turn the phone back on and see if it's working. If it is working, make sure you have some not-conductive spacer on the back of the connector before you reassemble (see the foam in the pictures above - that puts pressure on the cable to keep it from popping off, and replacement screens often don't have it). If it still isn't working you have either a faulty screen or a more serious problem on the logic board.

4GB is the official max, but 6GB works. It's a matter of what Apple says it supports and what it will actually recognize in real life.

Yes, this can be caused by the connector - clean with alcohol and inspect the pins. A small bit of dirt or glass from the old LCD can keep it from fully seating, and it's easy for someone to have damaged a pin when removing the old LCD. If you have a microscope look at the pins and use a needle to try to gently move them - if they shift they're not soldered. Some flux and a reflow should fix it. The other cause, which is, unfortunately, more likely and more common but much more difficult to repair, is the touch control IC, numbered U2402 on the schematics (google that and you'll find videos of the symptoms). As mentioned, much more difficult to repair

All Macbooks (save the new Retina Macbook which uses a USB-C charging port) use nominally 20V power supplies (the magsafe chargers, 20V will be marked on the bottom of them). In actuality the peak output voltage is under 19V (18.5V as you mentioned is normal), the same as almost all other laptops. However, note that this is peak. The actual supply voltage depends on the draw required (which depends on charge state of battery and workload) and will be either approximately 14.5V, 16.5V or 18.5V. So 16.6V is normal. Hope that helps!

Vacuums use AC motors that aren't (easily) reversible, so it's likely nothing particularly serious. All vacuums have an air inlet and outlet - normally the inlet is at the power head and the outlet is in around the bag/filter unit. Some vacuums have hoses that connect to the blower motor, one for inlet one for outlet. It sounds like your Bissell has this and he flipped these around so that it's now pulling through the filter and blowing out the power head. Make him vacuum for a week as punishment.

I'll assume you're running Windows on your computer. This error means the computer isn't able to find a bootable drive. It can be caused by a few different things. First off, make sure you have no CDs in the drive and no USB drives attached to your computer. Try restarting. The reason for this is that if the computer thinks the USB drive or CD is bootable and if the BIOS is set to boot first from USB or CD it might not bother checking your hard drive at all, instead just giving this error. If that doesn't work your problem is either a hardware fault (usually that would be a failing hard drive) or a corrupt operating system. I'd suggest getting a Linux LiveCD and running an extended SMART test on the hard drive. If it passes, try re-installing Windows. If it doesn't, you'll have to replace the drive.

No, U2 is for USB communication and power management and wouldn't do this. Most likely it's U6, which is 74LVC1G32GF in a SOT891 package. That assumes you didn't open it after it dropped and before this problem occurred and accidentally swapped screws on the LCD connector cover place - long screw damage causes this behaviour and is very difficult to repair.

Hi, This is a really easy repair once you get it open. To open it, remove the stylus and then use a plastic opening tool between the glass and the plastic frame around the tablet to separate the two - you'll hear clips click as you go. This will let the back come off. Sounds easy but it's a pain sometimes. Anyway, once you've got that done there's a couple screws holding the old port and flex cable. Remove them, then unclip the flex and put the new one on. Putting it back together is much easier than tearing it apart. There's a video of the process here.