Arcing may be visible or audible and result in readily detectable levels
of ozone. Note that very slight traces of ozone may not indicate anything
significant but if the TV smells like an office copier, there is probably
some discharge taking place.
|NotTaR of Television Sets : Arcing from flyback or vicinity
1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying.
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WARNING: It is possible for arcing to develop as a result of excessive high
voltage. Symptoms might be a smaller than normal excessively bright picture
but this may not be able to be confirmed until the flyback is repaired or
replaced. See the section: Excessive high voltage.
- On the HV output, it will probably be a loud snapping sound (due to the
capacitance of the CRT) with associated blue/white sparks up to an inch or
more in length. If the arc length is short enough, this may turn into a
nearly continuous sizzling sound with yellow/orange arc and melting/burning
- Prior to the HV rectifier, it will likely be a continuous sizzle with
orange/yellow/white arc and melting/burning plastic or circuit board
- Internal arcing in the flyback may be audible and eventually result in
a bulging and/or cracked case (if some other component doesn't fail first
as this would take some time to develop).
- A corona discharge without actual sparks or a visible well defined arc
is also possible. This may be visible in a totally dark room, possibly
more likely when the humidity is high. A thorough cleaning to remove all
dust and grime may be all that is needed in this case.
- If the arc is coming from a specific point on the flyback - a crack or
pinhole - this may be patched well enough to confirm that the rest of the
TV is operational and a new flyback is worth the money. Otherwise, there
is no way of knowing if the arcing may have damaged other circuitry until
a replacement flyback - possibly money wasted - arrives.
To attempt a repair, scrape off any dirt or carbon that is present along the
path of the arcing and its vicinity. Then, clean the area thoroughly with
alcohol and dry completely. Otherwise, the dirt and carbon will just act as
a good conductor and the arcing will continue under your repair! Several
layers of plastic electrical tape may be adequate for testing. Multiple
coats of high voltage sealer or non-corroding RTV silicone (if it smells like
vinegar - acetic acid - as it cures, this may get in and affect the windings)
would be better if the objective is an actual repair. A thick layer of
Epoxy may be even better and affected less by possible HV corona. Either of
these may prove to be a permanent fix although starting the search for a
source for a new flyback would not hurt just in case. The arc most likely
did damage the insulation internally which may or may not be a problem in
Also see the section: Dave's complete procedure for
repair of an arcing flyback.
- In some cases, the pinhole or crack is an indication of a more serious
problem - overheating due to shorted windings in the flyback or excessive
- If the arc is from one of the sparkgaps around the CRT, the CRT socket,
or the plastic 'alignment base' on the CRT itself, this could also be a
flyback problem indicating internal shorts in the focus/screen network.
- If the arcing is inside the CRT, this could indicate a bad CRT or a problem
with the flyback focus/screen network and no or inadequate sparkgap
Where repair seems possible, first, clean the areas around the arc thoroughly
and then try several layers of plastic electrical tape. If the TV works
normally for say, an hour, then there is probably nothing else wrong and you
can try for a proper sealing job or hope that tape holds out (put a few more
layers on - each is good for about 8-10 kV theoretically).
However, replacement of the flyback really is the best alternative to minimize
risk of future problems. This is the only option where there could be a
potential issue of liability should subsequent failure result in a fire.
Once I had a TV where the main problem was a cracked flyback arcing
but this took out one of the fusable resistors for the power supply to
the VERTICAL output so the symptoms included a single horizontal line.
Don't ask me to explain - replacing that resistor and the flyback (the
flyback tested good, but this was for someone else) fixed the TV.
In another case, a pinhole developed in the flyback casing probably
due to poor plastic molding at the time of manufacture. This resulted in
a most spectacular case of sparking to a nearby bracket. A few layers of
electrical tape was all that was needed to affect a permanent repair.
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