Maker Pro
Maker Pro

Need help on diagnosing TV with bad HO-Stage

A

Adrian Glaubitz

Jan 1, 1970
0
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
 
A

Adrian Glaubitz

Jan 1, 1970
0
Hello,

Adrian said:
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
 
B

b

Jan 1, 1970
0
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.

I have no record of the schneider 9.6 chassis. are you sure it is
schneider not beko or something? how old is the set? post some jpegs
on fileden.com or you send it and we can try and give more specific
help.

re: fault: likely open resistor or bad cap in the RGB stage. star on
CRT neck pcb and trace it back from there.
-b
 
A

Adrian Glaubitz

Jan 1, 1970
0
Hello,
I have no record of the schneider 9.6 chassis. are you sure it is
schneider not beko or something? how old is the set? post some jpegs
on fileden.com or you send it and we can try and give more specific
help.

re: fault: likely open resistor or bad cap in the RGB stage. star on
CRT neck pcb and trace it back from there.
-b

It's definetely a Schneider 9.6 chassis, it's clearly printed on the PCB
.. I am busy today, but I will do further measurements on the
CRT-neck-board tonight. Thanks for all your help so far !

Adrian
 
Top