I do not have much experience with the Samsung LED DLP HLT6187/6189 series, but I am sure I can be of some assistance.
Thank you for the detailed break down! It will help a lot if we have to trouble shoot down to replacing more internal parts like the SMPS board. We would however, need to begin with the basics, like:
-when was the last time you changed the lamp on the TV and how long did it last?
-where did you purchase the lamp and did they guarantee it was a genuine Philips brand lamp?
The reason I ask is because the type of malfunction is caused very often by a spent or defective lamp. Seems like an obvious place to start. Now its worth mentioning for further knowledge that your DLP RPTV Samsung HLT6187S uses a Bulb Model BP47-00023A, can you verify this off the lamp code sticker on the lamp or owners manual?
Thank you and I look forward to getting to a resolution!