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Need help on diagnosing TV with bad HO-Stage

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

Reply to
Adrian Glaubitz
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actually a

but

are glowing,

(type S2055N).

least for DC) on

as suggested by

transformer

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

Reply to
Adrian Glaubitz

No hints but you'll need a diagram to back track to where your video is lost. Do you have any sound? If not your problem 'could' be early in the signal path.

Reply to
Meat Plow

actually a

but

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

Reply to
b

No Screen supply to the CRT Drive Board, Check the source for open resistor, shorted diode, leaky electrolytic, Etc. Derived off the LOPT.

Reply to
Art

The OP went on in a follow up to clarify that if he turned the screen voltage up he got a raster albeit no snow or OSD.

Reply to
Meat Plow

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

Reply to
Adrian Glaubitz

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