DISCLAIMER - If you attempt to repair your own set, expect to void any warranty that might still exist. If you do additional damage, it's your own responsibility. Further, you are working with an appliance that is powered from you house mains. There is risk of shock with the potential of death or serious harm. Know what you are doing, and how to work safely with an electrical appliance.
Recently my 3+ year old 40" Samsung LCD TV started taking a long time to start up, with several cycles of relays clicking. In searching the net I found that others were having similar problems. Apparently, Samsung's power supply on several LCD models was somewhat under-designed, with four capacitors that slowly fail over time and which leads to the symptoms in the title.
There are several options for repair: 1) Take the set to a qualified repair shop (est $300 - $500). 2) Buy a new, replacement, power supply ($100 - $175). 3) Replace the offending capacitors ($4.00 - $15.00)
I chose option 3, spending $15.00 for a Samsung repair kit (contains 4-1000 uF, 25V, 105 degree C capacitors and "instructions"). If you want to keep the costs to a minimum, you can order an appropriate set of capacitors from Digi-Key or Mouser for about $0.65 each + s/h.
Tools you need:
Phillips screw driver able to reach recessed screws (about 1" deep)
Soldering Iron for general purpose electronic components.
Note: According to the Samsung repair kit instructions, this repair works with the following models:
Step 1: Remove the back of the set
Place monitor face down on a cushioned table. Remove screws from cover and remove screws from the stand. (If stand is attached)
I have an optional wall mount setup, requiring removal of the wall mount hardware from the rear cover - a total of 4 screws.
Step 2: Disconnect and Remove the power supply
There are seven screws securing the power supply, as well as the various cable connecting to other components. Remove the cables, remove the screws, and then lift out the power supply.
IMPORTANT NOTE - While capacitors are not particularly sensitive to Electrostatic Discharge (ESD), most of the components on the power supply and other boards ARE! Take appropriate measure to avoid static discharge (grounding straps, etc.), or risk totally frying your set's electronics. Should this occur, you're no longer facing an inexpensive repair.
Step 3: Identify, De-Solder, and remove the failing capacitors
There are four electrolytic capacitors to be removed: CM812, CM811, CM817, CS806. These are clearly noted on both the front and rear surfaces of the power supply's circuit board. (If you need a tutorial on how to de-solder "thru-hole" components, there are both text and video available on the net.)
You will likely see that the four capacitors of interest display bulging caps, and may even be leaking material. On my set, only one showed any leakage, but all four were bulging. The circuit they were used in is marked at 5.4V. Based on my readings in electronics, capacitors should, in general, be rated for a voltage that is at least double the planned circuit. Given that the original capacitors are rated at 10V, it would seem to indicate that fudging a bit here can lead to premature failure.
Step 4: Solder-in the replacement capacitors
The capacitors are polarized. This means you MUST pay attention to the positive and negative leads on the capacitors. The polarity is clearly identified on both the capacitors, there is a stripe down the side of a polarized capacitor with the minus sign, and the circuit board (both front and back indicate the polarity). Failure to match polarity is BAD. At the best, the capacitors will fail, in the worst case, they explode, and I assume, don't do anything good to the circuit board either.
Step 5: Replace the repaired power supply and attach the rear cover
Replace your newly repaired power supply, connect the internal cables to the other components. Re-attach the rear cover, stand (if used), or wall mount brackets. Attach the external cables (Video, Antenna, etc.). And, finally, plug in the power cord. If all has gone well, press the power button and you'll see your set power up as it did when it was new.
NOTE: The photo of my working TV is NOT representative of the image! The horizontal striations are an artifact.
Step 6: Other Resources
You may find the following useful:
Samsung LCD Power Supply Repair Kit - BN44-00167A
Samsung Replacement Power Supply - BN44-00167F
Digi-Key - www.digikey.com