It would be rather difficult for us to verify this as the problem because it require having hands on the device. However, the symptoms are similar to what you're concerned about. If you want to find out the cost of the part, you can locate it here for this TV: http://www.samsungparts.com/Products/Parts_and_Accessories/HLT5687SX/XAA/Default.aspx
But I'd check first to make sure it's not something simpler like replacing the lamp or dust on the lamp. Do you need contact info for a local authorized service center?
-- HD Tech
My Samsung Model number is HLT5687SXJXAA and the S/N is AH5V3CKP800065F I have had this Unit for a couple of years but it is rarely used as it is in my second home. Just recently I have been getting black dots on the screen, its seems to get a little better when the tv has been on a while. I called Samsung and they told me there is nothing they can do to help me. I have a reference # 5103529341. I understand that it might be the DMD Chip which is giving me the problem. I would like to verify this before I have a tech come out to my home. I also asked samsung if they would be willing to send me a new chip and I would pay to have it installed but they said that they could not accomodate me and that I was responsible for the total repair which is close to five hundred dollars. Any help would be greatly appreciated.