LCD Monitor Repair, Samsung...

Two failed LCD monitors, nice Samsung 216BW 22" widescreen displays. Much better than my current monitor. Having had some success repairing failed LCD monitors in the past, this was worth a go. Get the screwdriver...

I previously posted about my experience repairing a Viewsonic display. The post continues to draw web traffic at a surprising rate. Thus I will post about my experience with this monitor, in hopes the information can be of use to others who have trouble and need some information.

The Samsung SyncMaster 216BW comes apart far more easily than many other LCD monitors I have worked on. Indeed, I was impressed with the entire design. A simple and well designed assembly, easy to build, easy to work on. Something to consider if I ever buy a new monitor.

In these directions I will talk about the monitor as seen from the rear, with the screen face down on a table and the stand towards the viewer. Thus the power cord plugs in on the left and the video cable on the right.

• Before disassembly, disconnect all cords and cables from the monitor to remove any dangerous voltages from the monitor. The high voltage power supplies inside will take a few moments to power down, by the time you get inside everything should be safe. Reassembly of this monitor is pretty easy, you can fully reassemble before applying power and testing. (Yes! I have to include this warning!)
  
  
• Remove the monitor stand by removing the three screws found just above the base. The stand then slides out towards you.
  
  
• Remove the three screws across the bottom of the monitor, one at each corner and one in the center, where the base attached.
  
  
• Pry the case open gently, starting at the lower edge. It should come completely open relatively easily, with some popping sounds as the plastic retaining clips come free.
  
  
  

  The high voltage backlight connectors of the Samsung SyncMaster 216BW
• Unplug the connector where a small cable runs to the power and menu button assembly. The small tab on the top side of the connector must be pinched to release the catch.
  
  
• Remove the metal panel covering the backlight connectors. This is the panel that runs down the left side of the rear metal shielding. It is held in place by four tabs, two on each side.
  
  
• Mark the high voltage backlight connectors so that they can be reconnected in the correct places. There are two connectors on each supply. I marked one connector with a permanent pen and put a dot on the power supply to match. (note the marks in the photo at right)
  
  
  

  The LCD panel connector of a Samsung SyncMaster 216BW
• Unplug the high voltage backlight connectors. These have locking clips much like the power switch connector that must be pinched to release.
  
  
• Unplug the wide ribbon cable the connects to the LCD panel. There are two metal tabs, one on each side of the connector. Squeeze these tabs and gently pull the connector free.
  
  
• Pop free the rear shield holding the control board and the power supply. Everything is now exposed and ready to work on.
  
  
• There are two PCB assemblies. The power supply is easily recognized with the line cord connector, a tan color, and a lot of large capacitors and several transformers. The control PCB has the video connectors, and a large flat cable leading to the LCD panel. We are usually interested in the power supply board and will remove it.
  
  
  

  The power supply PCB of a Samsung SyncMaster 216BW
• Disconnect the cable that carries power between the two PCB's. Again there is a small tab that must be pinched to remove. Press the tab and gently tug at the connector.
  
  
• Remove the screws holding the power supply in place. On the left side it simply sits in a slot created by some bits of metalwork. Note the small metal part used to complete the shield under the power connector.
  
  
• Remove the power supply PCB from the monitor for repair.
  
  
• Reassembly is simply the reverse of disassembly. Just don't miss any of those connectors, read backwards through these instructions as a checklist.

At this point we have exposed the most likely area for electrical issues. I had two monitors to repair. The first was exhibiting an unstable/flickering display. Replacing the large power supply capacitors was successful in the case of this monitor. I replaced all six large power supply caps with parts that had better ratings. I had no 820μF parts on hand, but I did have 1000μF 25V 105°C rated capacitors. Since the replacement caps were slightly larger I had to lay one down and secure with RTV to make all of them fit. The larger high voltage capacitor (the black one lying down in the photo at right) tested good and was left in place.

In the second monitor I had expected to find the same capacitor problem, but this proved not the case for this monitor. Here the issue was a failed backlight supply, so I concentrated the search in this area of the power board. I removed and tested the capacitors, finding no problem. Replacing the capacitors anyway I went on the examine the PCB more closely. Looking close I noted a resistor slightly out of place on the solder side of the board. These are very small parts, 0604 components, I pulled the cover off my stereo microscope to get a better look.

The resistor had taken a blow at some time, shearing it off the pads. This must have happened during manufacture, as the PCB is otherwise fully protected inside the case. It was not fully off the pads, still jammed between the solder fillets, and still in electrical contact, at least for a few years of use.

Yeah, I got lucky here.

Removing the resistor, cleaning the pads and replacing was a bit of fine work under the microscope. The plated terminations had also been damaged on the bottom of the resistor, but the element was fine. I just flowed the solder high and a bit over the top of the resistor to provide a permanent fix.

Were my repairs successful? The first monitor in question is the display I am using to enter this posting. Working perfectly for over a week now, with a clean and crisp display. I ran the second monitor for a few days to give it a thorough test, no problems. Then put it aside as a spare for the moment.

It has always surprised me how many issues can be found with a simple visual inspection of the failed circuit board. So many times I have found it is often worth taking a failed device apart and seeing if you can find the problem. We are talking a failed device, something that is destined for the trash heap if not fixed, no risk in getting out the screwdriver and having a peek. You always learn when taking something apart, just through the challenge, and through observing how it was assembled. Sometimes the failed component is obvious, at least you know why it failed. On occasion it is possible to repair the failure, in which case you have a functioning device back. In any case you always learn.