Samsung Syncmaster 305T

This monitor belongs to a family of extremely early 29" monitors. As such, it has some problems associated with early technology.

Common failures
Some typical failure modes specific to this family of monitors include:
 * Power supply deregulation
 * Backlight dulling/dropout
 * Display artifacts

Disassembly
Remove the stand with 4 phillips screws. Use a small plastic pry tool to free the back plastic lid from the frame. You will have to support it in a few areas while you work around the sidesit's very large. Remove the plastic film covering the CCFL backlightit can crack very easily, so just get it out of the way. Remove the screws holding the metal shielding that supports the boards. Unplug necessary connectors on the sides.

Power Supply Deregulation
This monitor tends to get extremely hot, and this manifests in a variety of ways. Although, the most typical is for the heat to dry up the electrolytic capacitors in the power supply. This causes ripple to develop on the supply rails, causing inconsistent behavior or, in rare cases, damage to components. If you suspect that your monitor has this issue, you should verify before you do anything to the boards or order parts. The PCB with the socket for the mains power is the power supply (PSU) board. There are clearly labelled voltage test points on this board, so you should probe and see if there is excessive ripple (using an oscilloscope, look for 120Hz) and if the DC component of the signal is appropriate (use a multimeter in DC volts mode). You should be careful, there is also high voltage generated for the CCFL backlight here. If you find that there is ripple, you are better off just replacing all of the capacitors than trying to find the busted one. They all basically act as voltage buffer to ground, which means they are essentially connected in parallel. Therefore, failure of one will make them all appear bad- there is no real logical way to go about replacing them once you do a visual inspection for any obvious failures.

Backlight dulling
This is a bit less common. For this, make sure the high voltage for the backlight is present from the PSU board. If this looks OK, but you still have a dim display at full brightness, it may be that the lights have just aged. You may be able to find a replacement that is mechanically compatible, but I found it much easier to just replace this with a strip of super-bright LEDs. You do have to either find a strip that is compatible with the voltage levels you can get off the board, or design a DC-to-DC converter to get the right voltage for the strip you put in, however.

Display artifacts
This monitor suffers from a really unique problem, in that the display ASIC will basically get so hot that it will desolder itself from the board. It is a huge BGA chip so this is quite a feat. I have created a remedy for this that has reliably worked for an extended period of time for me, I will detail it below. The first thing to do once you see these artifacts is to repair the chip. You should either remove and bake the board in the oven or use a rework gun to realign the chip. You should do this with no pressure applied to the chip, the surface tension of the solder will carry it into the correct area. Wait for the chip to cool, then turn everything on and make sure the artifacts are gone. If they are, you can proceed with a cooling solution. I recommend to cut the metal shielding over the ASIC and use some thermal paste to adhere a small heatsink. The size of the heatsink is very critical- there is not a lot of space back here. You need it to be such that the heatsink does not touch the plastic backing when the monitor is reassembled. If it is touching, the next time it reflows itself, it will smash the chip down and the bridging on the BGA will be unfixable. Once you get an appropriate heatsink, I recommend to take a small 12V fan and tack it on. Solder the leads between the 18V (black) and 24V (red) test pointsthis makes the 12V bias needed to drive the fan. If you get a nice tiny one, it can fit neatly with the metal shielding that goes back on when reassembling and hold everything in place. This should fix your problem for approximately a year, give or take a few months. I find I need to rework mine every 8-ish months, but I live in a hotter place.