I've got a 19 years old 21" Sony CRT TV. Model- KV2167MT. Althought the picture quality is excellent, I've recently noticed that the picture has got slightly curved inwards from the sides.

The bend is from both sides but the bend from the right side is comparatevely more than on left side. In most pictures, the bend is not noticeable but in certain pictures (like in which have got large box almost the same size of screen area or got straight line on the sides, the curve is clearly noticeable)

A Sony technician had came to fix another fault of low brightness in this TV and repaired the fault by detecting a small faulty component. After that when I told about this picture curving fault, he without doing any testing told me something about yoke and that he cannot rectify this fault.

My questions
So, what are the possible reasons for this fault? If due to a faulty component, which is that component? Could this be corrected by some adjustments?

All that the Sony engineer told me could really be true that its certainly a yoke problem? (earlier this engineer, for low brightness told me that this problem is due to faulty IC. But later he made a more detailed check and found out that a faulty resistor was responsible for that brigtness problem.. Not the IC!)

Pls help

Thanks
R Solomon