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Samsung T200HD backlight issues
Hello, I have tried to solve problem with my monitor for quite a while now, yet unsuccessfully and hopefully someone will be able to help me.
When I got this monitor it was suffering from 2 seconds to black problem. When I have disassembled it I haven't seen any bulged caps, nothing wrong visually at all, but as I didn't have an ESR meter I decided to replace all caps on power board, after doing so I tried to switch it on, nothing changed. Then I have noticed that some solder joints on main board looked like they have suffered from oxidation, I tried to reflow the main board using some alcohol based flux, after that it started to work just fine with backlight going off extremely rarely.. Well, just for some time. When summer came in and ambient temperatures have raised I started having a lot of issues again, but at least this time it was not 2 seconds to black, or at least I thought so.. Now backlight goes off randomly after about 20-40 minutes of flawless work. The only thing I could think of at this point was cold solder joints on CFL lamps themselves, so I have dismantled the LCD panel, tried to slightly pull the CFL lamp wires to check if it was poor connection due to cold solder or burned wires, nope, wires were not burned at the ends and I was unable to pull out any of the wires, after doing so just in case I might have probably lost the contact I assembled the monitor back, and checked, no difference. Primaries and secondaries also seem so be fine (difference is well within 1%). Maybe someone has any ideas what might be the issue?
P.S. I have noticed that when backlight goes off I'm loosing voltage on Dimmer pin which goes from main board to inverter board.
Photos of the boards attached.
Tools I possess now:
Hot air soldering station.
Mega328 based LCR meter (includes capacitor ESR meter).
Regular soldering iron.
Digital and analog multimeters.
When I got this monitor it was suffering from 2 seconds to black problem. When I have disassembled it I haven't seen any bulged caps, nothing wrong visually at all, but as I didn't have an ESR meter I decided to replace all caps on power board, after doing so I tried to switch it on, nothing changed. Then I have noticed that some solder joints on main board looked like they have suffered from oxidation, I tried to reflow the main board using some alcohol based flux, after that it started to work just fine with backlight going off extremely rarely.. Well, just for some time. When summer came in and ambient temperatures have raised I started having a lot of issues again, but at least this time it was not 2 seconds to black, or at least I thought so.. Now backlight goes off randomly after about 20-40 minutes of flawless work. The only thing I could think of at this point was cold solder joints on CFL lamps themselves, so I have dismantled the LCD panel, tried to slightly pull the CFL lamp wires to check if it was poor connection due to cold solder or burned wires, nope, wires were not burned at the ends and I was unable to pull out any of the wires, after doing so just in case I might have probably lost the contact I assembled the monitor back, and checked, no difference. Primaries and secondaries also seem so be fine (difference is well within 1%). Maybe someone has any ideas what might be the issue?
P.S. I have noticed that when backlight goes off I'm loosing voltage on Dimmer pin which goes from main board to inverter board.
Photos of the boards attached.
Tools I possess now:
Hot air soldering station.
Mega328 based LCR meter (includes capacitor ESR meter).
Regular soldering iron.
Digital and analog multimeters.
Attached Files
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