🚀 go-pugleaf

In article <1992Dec28.194342.25050@comp.lancs.ac.uk> ega029@comp.lancs.ac.uk (Lami Kaya) writes:
>
>Hi,
>
>I have got an old colour TV set. When it is left on for more than
>an hour, the picture gets distorted and the colour of the screen
>changes to some strange mixture, also you can hear 'chat chut' 
>sounds, as if something is burning inside. I am not intending to
>repair the set, but I would be pleased if I knew the reason/s for
>these problems, any suggestion? 

This sounds like a temperature-drift  or an adjustment problem in
either  the  main  power   regulator  circuit  or  in  the  extra
high tension (EHT) generator/horizontal deflection circuit combi-
nation.  The sounds probably come from sparks arising from inade-
quate insulation in the extra high tension circuitry,  especially
in  the thick cable that is attached to the tube at some point on
its side.  This cable carries approximately twenty-five  thousand
(25000)  volts  to  the  front inner coating of the picture tube.
Bare conductors carrying this high a  voltage  must  be  kept  at
least five  centimeters  away from any other  conductor  to avoid
leakage and sparks under a wide range of air moisture levels.

It seems that the EHT is not adequately  insulated,  or  the  EHT
generator is misadjusted such that it generates more voltage than
it has to.  In either case, sparks and excessive leakage will oc-
cur.   The  sparks produce ozone, which is a poisonous gas with a
garlic odour.  Leakage through plastic,  bakelite,  and  phenolic
materials used for insulation, on the other hand, produce organic
gases with typical odours.

The remedy is to have a repair technician check the  EHT  circuit
starting  from  the  tube,  towards  the  EHT  rectifier, the EHT
transformer and the horizontal deflection/EHT  driving  electron-
ics.  The  main  power  supply may have to be checked, too.  They
may  be  found  to be "fubar" (fouled up beyond all recognition).
Do  not  attempt  to  repair it yourself if you do not know  what
25000 volts stored  in  a  TV tube can do,  not  to  mention  the
various  voltages up to 250  VDC  travelling  around  the printed
circuit  boards.  The  latter  are even  more  dangerous  because
they can supply larger currents.

(To avoid such problems altogether, use a LCD pocket TV :-)

>
>Lami

A happy new year to all,

Mustafa

-- 
Mustafa Kocaturk   mustafa@seas.smu.edu  EE Dept., Room 305A, Caruth Bldg.
Home: 214-706-5954  Office: 214-768-1475  SMU Box 753190, Dallas, TX 75275