Arfa, You're a diamond geezer! Cheers!
I found the service manual online, identified the 'field output chip' as :
IC451 LA7845N VERTICAL OUTPUT (Sanyo call it a 'Vertical Deflection Output
Circuit')
a 7 pin SIP7H package on the main pcb. Soldered all the pins as you
suggested (a pin at one end was hard to get the solder to flow on despite
using lots of flux, so I guess it was badly oxidized from arcing and was the
problem), and the TV's now 100% working :-)
Three days without telly, I was starting to get the shakes!
Thanks again,

Scrim


"Arfa Daily" wrote in message
news

"Scrim" wrote in message
...
I'm experienced with electronics but don't know much about TV's. Can
anyone help me identify this problem?

Panasonic TX-W28R4
Recently: After switching on from cold every now and then the picture
starts to shrink in the vertical direction. I bang the top a few times
over a space of 15 minutes each time this happens after which it's warmed
up and works fine. Sometimes the picture shrinks to the bottom inch or
two of the screen and is scrambled. Occasionally the screen goes blank
and the TV shortly afterwards shuts itself off.

I lived with that but now the problem is worse. A few seconds after
switching on and nothing appearing to happen, there is a flash on the
screen of light collapsing towards the centre as the TV shuts off. I
can't use it at all any more.

I vacuumed the circuit boards free of dust and this gave me two more
days.
I just tried pulling/reinserted all the connectors but that hasn't
helped.

Any ideas gratefully received.

Scrim

Bad joints on the field output chip. Very common on Pans of a few years
old. Fix it now before the IC fails from all the arcing and flashing about
on its pins, or the board starts to burn up around the bad joint. Even if
you can't actually see anything that looks like a bad joint on any of the
pins, reflow them with some new solder anyway.

Arfa