Samsung TV - No Picture

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rbearl
rbearl's picture
Samsung TV - No Picture

I recently acquired a Samsung TXD2759 (aka
model TXE2759) TV from a neighbour.

When it is powered on, there is just a flash
on the screen (same when shutting it off). No picture at all. The sound is perfect (actually
it's incredible).

With power on, there is no "noticeable" whine from the horizontal output but everything seems to check out - including the H.O.T.

Ater looking over the internal circuitry, I noticed that 3 large electrolytics (200V and
up) are bulged - but test okay.

What could cause the horizontal circuit to be dead but provide power to the other components?
Does anyone know if the horizontal circuit a key part of the power supply on this chassis?

If these questions seem a bit stupid, I am sorry but although I've worked in electronics for many years, I always tried to stay away from TVs.

Thanks.

R. Earl

Techrat
Techrat's picture
Bulging capacitors usually

Bulging capacitors usually indicate an overvoltage condition has ocurred, or a rectifier has shorted sending them some AC...... something boiled the electrolyte. Does this set have B+ voltage at the collector of the horiz. out? Is it within tolerance (around 135v for most sets)? Sometimes a faulty feedback capacitor (somewhat out of tolerance, but checking good) in the power supply will cause the power supply voltages to shift upward, causing these symptoms - the Horiz. drive is shut off to prevent X-rays when the voltage is too high. Replace the bulging caps, and check the ESR of all the caps 100uf or smaller in the power supply, this should clear it up.

 

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