Back when I was in Infant School (many years ago), we had a TV that had to be hit quite hard on the side a few times before Channel 4 would work. BBC and ITV were fine, but at the time all the good schools progs were on C4.
Especially the ones we could clap and sing along to. Ahh, good times. :)
I had a batch of DGM TFTs a few years back that would stop accepting signal.... dropping them on the desk from a distance of 6 inches usually squeezed an extra 3 weeks of life out of them, eventually this method stopped working and they'd have to be chucked.
I used to do the lift and drop on a temperamental 15" Viglen CRT in one of the suites - the kids were always impressed.
I am told that engineers who used to support BBC Masters used to lift an edge about a quarter to half an inch off the desk and then let it drop. This would apparently reseat any of the chips that had moved due to warming/cooling as the computer worked.
The guy who told me this was quite misty-eyed at the time of telling [as if thinking: 'Ah those were the days...']
I slap the backs of Neovo TFTs as it helps the connection to the power coil (Only if we don't have the time to strip them down and fix them properly) :D
When as a child I used to watch in awe at my father thumping the TV to reseat the valves and it often worked especially when he wanted to watch the football. :D
Tandon ST506 drives used to suffer from "stiction" which prevented them from spinning up. It was thought to be a combination of cold lubricant and unmatched transistors in the motor control. If you lifted the computer and gave it a sharp clockwise twist, this would invariably be enough to get it to cough into life. The checkout girl in a busy Florida hotel was most impressed when I showed her. As were the 20 odd people waiting to check out.