TV ON switch won't latch



I have a CRT type SONY 27 inch TV Model KV27T530. It's between 10 to
15 years old and still shows a great sharp picture in excellent color.
I have Cable TV for the basic channels (2 to 13) plus the first tier
of extra channels. A month or so ago it could show only the first
tier channels and would not even display the Channel number for the
second tier. So I took off the back cover to reseat all the
connectors. After that the ON switch wouldn't latch. It comes on and
switches itself off after a few seconds. What should I be looking for
to fix it?

I used to be an electronics tech and had fixed minor TV problems
before. This TV set isn't worth fixing at a shop. I am sure its
basically working OK and I don't like dumping equipment that can be
fixed. I'd be happy if it can just receive the first tier channels.
I've bought a large flat panel TV to watch the coming Olympics. So
fixing the SONY is something I can take my time on to troubleshoot.

Thanks in advance.
.