I've bought a cheap broken laptop on eBay for around 20EUR with the description "turns on briefly the fan and the shuts down, no image". The laptop was actually in pretty good condition, came with a working battery and charger and RAM, but without any hard-drive. A quick search on the Internet turned up the fact that these laptops usually die from heat, having inadequate cooling on the integrated video card. I recovered the laptop by using a makeshift heat shield made from a sandwich of aluminium foil and cardboard an using a heatgun (paint stripper) to slowly heat the chip. A blob of leaded solder was used as reflow indicator, knowing that the leadfree solder melts at higher temperatures and the BGA balls take a while to heat up (being under the chip). A cheap multimeter was used as a temperature indicator, with the thermocouple pressed against the chip body. The cardboard started smoking after a while but this did not affect the operation in any way. The ...
Electronics and programming interspersed at various levels of difficulty.