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Adrian Glaubitz Adrian Glaubitz is offline
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Default Need help on diagnosing TV with bad HO-Stage

Hello,

Adrian Glaubitz wrote:
Hello,

I have a Lifetec LT-7079VTS television (German no-name brand), which is actually a
Schneider TV 9.6 chassis. The problem with the set is that it can be turned on but
no raster comes up. The HV is present (electrostatic field) and the filaments are glowing,
but as said before no raster. I have tested the LOPT (unsoldered) and its okay (type S2055N).
The weird thing is though that Basis and Emitter of the LOPT are shorted (at least for DC) on
board so I suppose the LOPT cannot work properly. I have tested a lot of parts as suggested by
the EURAS repair-database but all of them are ok. I suppose the horizontal transformer
to be bad but I have no idea how to test it. Any ideas ?!?

Adrian


Okey, I got further. The short from emitter to collector is normal and
comes from the flyback coils (didn't know that before, read that in the
FAQ). I measured the B+ across C and E of the HOT and it reads about 140
Volts. If I turn the screen voltage, I can finally see a raster, but
there is still no picture (e.g. noise or OSD).

Any hints ?

Adrian