Originally Posted by
markelliott:
“Good job I came across this thread - http://forum.digitalspy.co.uk/board/...d.php?t=137127.
Did they give you a new TV, or did they repair it? Also, what does the 'HT' bit stand for? As you said 'HT coils'.”
Here goes, I'm a bit rusty so no guarantees given for absolute technical accuracy.
On the main board, there is a component known as the flyback tranformer - this converts the low tension (lowish voltage maybe 15v or so) voltage that runs around the circuit board into high tension (HT which can be 30,000v or more) which it then sends up a cable, the end of which is stuck to the top of the tube (looks a bit like a rubber suction pad). Basically, the cathode ray scans the picture from top to bottom, and when it gets to the bottom the HT cap releases its voltage in order to bring the beam back to the start - hence the name flyback.
The use of a coil to increase the voltage from LT to HT is fairly similar to the process that happens in a petrol car engine, with the HT cap being the spark plug end.
If there is a fault with the transformer, or with the cap it can cause a singing or fizzling noise - sometimes they will fizzle for a while, give a crack and go quiet for the rest of the day. There are other components that can sing or whistle such as capacitors, so there are a few variables.
If the set is under guarantee, make the phone call. Even if the engineer can't find the problem, ou have logged the fact that you have experienced a fault. It may need your TV to be taken away and soak tested to show the fault to the engineer, but it is worth getting the ball rolling while you have the warranty. Sony were always very fair with things like this, I've known them to replace sets that are no longer under warranty because of a recurring intermittent fault.