monitor for 2 seconds

[sizzle]

Hi!
Las week my samsung 940n just went black and now if powered off and on again it shows picture for about 2 seconds only.

What could be the problem ?

 

[GreenGiant]

sounds like a safety trigger is being tripped then immediately reset, cant say for certain though, could also be a power supply problem

Knowing samsung I would try contacting them to see if it is still under warranty, my friend picked up a dead samsung monitor at the local dump and called them up and they fixed it for free

 

[sizzle]

caps didnt look bad but i did replace them anyway cause 1 don't have LC meter.
Still the sama problem.
Where where to look for that safety trigger?
id doesn't reset itself.
power putton must be pressed.

 

[restorerjohn]

It is very likely the ccfl tube inverter transformer is the culprit. I have repaired many of these monitors and honestly, the most common issue is the ccfl inverter tx/former. Second most common is of course our friends the caps! Some 940s have twin individual transformers, others have one large one. The large ones do both tubes and fail due to internal arcing on the HV windings. It would all be ok except the circuitry monitors the balance of the two outputs and shuts the monitor off if there is a significant difference in the output of either side. If you remove the transformer and test the two sides (primary will be fine, test the resistance of the two secondaries) the resistance should be close- if it is more than 5% different you have some shorted turns. Just don't use a DMM, the inductance will give you a useless reading- use an old analogue meter or simply whack it in a few milliamp LED circuit and read off the voltage drop with your DMM.
The numbering will be something like TMS914429CT or TMS9xxxxxxx etc, on the twin type.

 

[sizzle]

one secondary does,t give any reading.
otheer gives 1,229k

 

[restorerjohn]

You can run both tubes off one side and parallel the output. That will allow it to function and not shut down. It will fail in time and won't be as bright, but the transformers are $40 and the monitor is worth nothing. Otherwise get a donor with a good Tx/former. I have several here with the same issue. There's not really enough room to fit either twin transformers or another half dead one under the metal can.
Pity as they are great monitors for clarity.

 

[sizzle]

Thanks for advise!