Since this site helped me fix my own expensive TV, I thought that I'd contribute my own experience with it in case it helps someone else in some way. I owe a large debt to this forum to save me from throwing out my cherished TV!
I purchased my Samsung PN64F8500 in November 2013 along with a 5 yr extended warrantee. The place I purchased it from went out of business about 2 years later. The TV died in Sept. 2016 - it clicked while trying to power on and only infrequently would actually turn on. Once it was on, it seems to work OK.
I called the service company and they sent a tech out to look at it. He diagnosed it to a bad Y-Main board, but could NOT find a replacement anywhere. I did not like any of the other LED TVs they offered as a replacement, so I took the cash buyout and purchased a 55" LG OLED by kicking in a few hundred $ more. (I really like the OLED, but still missed the 64" plasma.) That's when I began researching into this issue and stumbled on the AVS forum. I even purchased the service manual for the TV which promised to have schematics in it (it did NOT!).
For a couple years, I left the TV in our enclosed porch until I finally got serious about fixing it - which came a few weeks ago. I ordered 10 of the famous caps from Mouser (thanks to other posts!) and downloaded the Samsung service bulletins that someone else posted here.
Following the service bulletin for this issue, I removed the back and proceeded to check the voltages related to the cap failures. I did not see the voltages I was supposed to and was now unsure if my TV was actually exhibiting the related failure mode that the caps are supposed to fix. Further on-line research led me to other tips and eventually I found a small connector from the power supply to the X-Main board that was not quite seated fully enough to make good contact. (The service tech apparently didn't bother to make sure the TV was restored to its original state as I requested.) With the connector fully seated, I now measured the right voltages at the key test points.
It's important to note that there are a couple voltages (VS & VSCAN) that the tech bulletin instructs you to check and they will decay slowly if the TV has an issue related to the VSCAN failure that can be fixed by replacing the three 10uF caps. As a further check, I found that disconnecting one end of the flat ribbon cable between the Y-Main and the Main board will allow these voltages to remain steady because the error signal from the Y-Main board is blocked from the Main board and it does not automatically shutdown those voltages.
Now that I was reading the proper voltages at the test points, I could verify that they decayed slowly after I reconnected the flat ribbon cable (do this with the TV unplugged!). Satisfied that I was now looking at the exact VSCAN issue in this thread, I prepared to replace the caps. I chose to leave the board installed, so I placed the TV on top of a table so I could access the caps easily while sitting comfortably. In addition to positioning a strong task light on the work area, I wore a headlamp to illuminate the area I was working. (Good lighting is very important in this type of work.)
Following the advice on this forum as well as the service bulletin, I snipped off the caps while leaving the leads as long as possible. I carefully tinned each of those leads with solder without heating the leads up too much to avoid causing connectivity issues with the solder connection to the multi-layer circuit board. I then snipped off the new caps from their carrier strips so they had about a half inch on each lead. I brushed on a small bead of solder on the lower part of these leads to prepare them for the tack solder to the old cap leads.
I tack soldered the middle cap first as suggested in the bulletin. This way, I was able to bend the cap slightly to either side as I worked on the two outside caps. I kept the soldering tip on the leads only as long as needed for the solder to melt together and hold the caps in place. My work was far from pretty, but it looked like things made a solid connection which is all that matters. After carefully inspecting my work to verify nothing was shorted and there was sufficient space between the leads and other components/pads, I plugged the TV in and heard that beautiful sing-song of the powering up sequence through the speakers!
By the time I went around to the front of the TV, it was already displaying the apps that it was updating. I did a check of the test point voltages to make sure they matched the voltages on the inside label and put the TV through its paces with audio and video tests and verifying the WiFi connection to make sure it connected to my Netflix account. Everything worked!
Note that replacing the three caps with ones of the same 10uF rating, the TV is less apt to drift from the calibrated voltages on the inside label. If the voltages do not match the ones on the label, then adjustment of the voltages is required or the TV could experience video anomalies or non-optimal picture quality. The service bulletin explains how to do this.
The TV has since replaced the LG OLED in our family room in time to watch the destruction of King's Landing in Game of Thrones. The operation was a success!
So - many thanks to members of this forum for providing the info I needed to perform this repair as well as links to service bulletins and replacement parts. If my little story helps even one person fix their own TV, then it was worth the time it took me to write it.