I have a Philips TeleVideo 14PV200

When you press the power switch on the side it comes on, but release
it and it either crackles for a while and then goes off, or just goes
straight off.
If you hold the power switch in for a few seconds and take the tv out
of standby and then release the switch, it stays on for about 20 mins
- an hour, then crackles and switches off.

My first guess is obviously something wrong with the switch