AWA tv - blue screen of death?

[tv addict]

hi,
just over a year ago I bought a 51cm colour tv from Big W store.AWA
brand and model no.W571. For the first year,no problems at all,now a
month later,now the warranty's run out (typical!) i've had to get it
fixed (?!) because suddenly one morning i turned it on and there was
the usual perfect sound but no picture as such.By that I mean just a
blue screen with very faint image in background.Sort of like looking at
a photo through a negative.Then within seconds that is replaced by just
the blue screen with faint white lines running across the screen.
I eventually found a technicial who could collect the tv and look at it
straight away. He wasn't sure what was causing the problem,saying it
could've been 3/4 things including the tube but that, that was the
least likely cause.
The following day he rang to confirm that it definately wasn't the tube
but there were stil 2/3 other things it could be. A couple of hours
later he said he'd found the problem,which was a bit too technical for
me to understand but said he could fix it and it would be probably
ready to collect later that day. It was! Again he tried to explain what
the problem was but it was too complicated,something to do with the
circuit board and something connected to the tube.
Anyway all was working fine,and now 4 days later the same problem has
occurred:( So despite forking out nearly $200AU to get it fixed
(supposedly) the problem still remains.Does anyone have any
suggestions?
It's been suggested that this time round something else could be
causing the same problem as opposed to any parts that were replaced.
Hope someone here has some suggestions and/or have had the same
problem. Sorry if my info has been a bit vague,but done my best to
describe the situation.
Thanks
John