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
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
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
Step 5: Replace the repaired power supply and attach the rear cover
NOTE: The photo of my working TV is NOT representative of the image! The horizontal striations are an artifact.