Anyone on the list remember the days when you had a TV repaired instead of
pitching it and getting a new one? :-)
I've got a 17" monitor that about 3 years old and a 27" TV that's closer to 5
years old and they both are whining. Talked my wife into getting a LCD monitor
so that I could have her year old monitor but not in the mood to replace the
TV right now.
Charles Craft wrote:
>
> Anyone fix TVs in a past life?
>
> Anyone on the list remember the days when you had a TV repaired instead of
> pitching it and getting a new one? :-)
>
> I've got a 17" monitor that about 3 years old and a 27" TV that's closer to 5
> years old and they both are whining. Talked my wife into getting a LCD monitor
> so that I could have her year old monitor but not in the mood to replace the
> TV right now.
>This is usually caused by the flyback transformer
>windings or ferrite loosening up due to heat and
>stress causing high frequency vibration or a
>possible arcing.
All the examples I have come across have a supersonic noise that drives me
crazy, and it has always been because something electronic has died in the
horizontal output stage and made the waveforms incorrect. The resulting
incorrect waveform radiates sound from the mechanical vibration of the LOPT
in an incorrect mode.
I have yet to come across a unit where the problem has been a mechanically
loose component.
> >This is usually caused by the flyback transformer
> >windings or ferrite loosening up due to heat and
> >stress causing high frequency vibration or a
> >possible arcing.
>
> All the examples I have come across have a supersonic noise that drives me
> crazy, and it has always been because something electronic has died in the
> horizontal output stage and made the waveforms incorrect. The resulting
> incorrect waveform radiates sound from the mechanical vibration of the LOPT
> in an incorrect mode.
>
> I have yet to come across a unit where the problem has been a mechanically
> loose component.
>
Newer flybacks are dipped in a rubber compound to seal it from moisture and
vibration. Some flybacks are made up of a two piece ferrite or iron powder core
with a non ferrous (brass) long screw and nut holding them together. On a
problem unit I had, I used a long plastic tool to push on the flyback winding
or core and was able to change the whine or eliminate it altogether. Tightening
the screw a little and "glpting" the core made the fix permanent. Just remember
to remove power and discharge the 2nd anode and all associated parts.
Rick
Alan B. Pearce wrote:
>
> >This is usually caused by the flyback transformer
> >windings or ferrite loosening up due to heat and
> >stress causing high frequency vibration or a
> >possible arcing.
> I have yet to come across a unit where the problem has been a mechanically
> loose component.
I've fixed hundreds of them. :o) We used to keep a
little bottle of "crazy glue" on the bench specifically
for that purpose.
Many of the TVs use a small inductor, multi winding,
in the Horiz deflection circuit. These often vibrate
until the ferrite C core cracks and then they make quite
a nasty noise. Normally fixed by unsoldering the part,
dousing in glue, dry etc, then replace in the set.
No performance penalties, and much cheaper than the
replacement part which was priced quite high.
The diagnosis was by pushing the part with a screwdriver
with the set running, and the squealing stopped.
-Roman
mitvma.mit.edu
