Electronics > Beginners
Dell LCD TV turns off by itself after a few seconds
kasumyku:
Hi everyone,
I just got a Dell Tv W3207C. It powers up, backlight comes on for a couple of seconds then it shuts of by itself. Only once I had it on for a bit longer and I could see onscreen menu for a brief moment then it disappeared and it shut off again.
Things that I tried and found so far:
-looked for obvious burn marks, swollen caps: seem to look OK
-checked power board output voltage: not OK. 3 pins should read 5Vdc but instead they read 1.591Vdc as bellow
Power board has 3 output connectors:
1st connector: +12VS reading 11.8Vdc
GND 0Vdc
+5V 1.591Vdc
+5V2-STBY 5Vdc
+3V 3Vdc
2nd connector: +24V 24.32 Vdc
GND 0Vdc
ON/OFF 0.466Vdc
3rd connector: GND 0Vdc
+24V 24.04Vdc
I removed T-con and inverter connectors one at a time to see if there is any difference in the output voltage but nothing changed.
I'm not sure if I really narrowed it down correctly to the power board or there's more to it. I also searched online for service manual and no luck.
Any advice would be really appreciated because I don't really know where to go from here due to my little knowledge of troubleshooting electronics to component level.
Thank you in advance!!
thinkfat:
Check all power rails for ground shorts. Might be a cracked filter cap. Check for heat sources, freeze spray can be helpful.
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dzseki:
I had a similar problem with a DELL mointor before, there, some of the CCFL tube connectors were "burnt". As there were some sort of preformed conductive rubber thingies those were holding the CCFL tubes in place and making the electrical contact too to the inverter. Some of them got corroded and failed to make proper contact and it was shutting down eventually. This monitor used an LG panel I think.
I managed to repair this with soldering all the CCFL tubes with a thin wire to the inverter contact, while I left the rubber stuff there for the mechanical support.
Brumby:
This may not be relevant, but it is a curiosity question:
Is this 1.591Vdc always around the same value - or does it change? If it does change, what is the timing?
If you have disconnected all off-board connections and the voltage is still low, then the likelihood there is a problem on the power board is going to be high. Can you get a good close-up photos of this board - top and bottom would be good. (Remember - good framing, good lighting and good focus make such photos more useful.)
MosherIV:
Hi
Good work so far.
--- Quote --- -looked for obvious burn marks, swollen caps: seem to look OK
--- End quote ---
Capacitors can fail without outward signs.
My bet is on capacitors on the 5V rail gone bad.
Try soldering new cap across this rail and see if the monitor starts working.
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