Reck said:
wow something wierd happened. lightning struck a house right across the
street from me, sounded like a bomb went off. scared the bajeezes out
of me. anyway i was watching TV at the time with my panasonic TV (not
sure what type or how to find out), now there are inverted patches of
color on the corners of the screen. it looks like sombody screwed up
the tint on 3 of the corners of the screen. how do i fix it? do i have
to buy a new TV now? somebody please help!
Lightning generates a magnetic pulse which affects the shadow mask in your
tube. In very simple terms, the shadow mask is a very fine metallic mesh
just behing the front of the screen which guides the electron beams onto the
correct colour phosphor dots. When it becomes magnetised, the electron beams
are 'pulled' slightly and fall onto the wrong dots, creating the patchy
effect.
Luckily, there is a device inside your TV called a 'degaussing coil'. When
you power on the set from cold, you may hear a buzz or surging noise. That
is the coil automatically removing any residual magnetic field from the
shadow mask. It is necessary because a shadow mask can become affected by
other means than lightning strikes, such as nearby magnets, like in
loudspeakers.
Unfortunately, a very large magnetic field can severely magnetise the shadow
mask to such a point that the built in degaussing coil is too weak to remove
it in a single, or even several, cycle(s). Also, a lightning strike can
damage TV circuitry so as 3T39 mentioned in his post, there may be physical
damage to the degaussing circuit.
However, the good news is that even if the degaussing circuit is damaged,
the repair should be trivial and not expensive. Conventional degaussing
circuits are theoretically far less susceptible to lightning strike damage
than the rest of your TV's circuitry, so the fact the TV still otherwise
works OK bodes well.
Try a few on/off power cycles (switching it off properly, not standby) and
see what happens. To do this you need to power on from cold, switch off,
leave for a few minutes and repeat. See if this makes the colour patches
fade. On powering on you may hear a slight momentary buzz or surge, which
will be the degaussing coil working to remove the magnetism from the tube.
If this doesn't work, (it might take several on/off cycles, or the patterns
may fade themselves over several days) contact a TV repair shop and get it
degaussed, and repaired if there's a fault.
Dave
