Hi Chris,
Reminiscent of the early LG plasmas which developed glitter as they aged - mostly when first turned on. Trick was to adjust Set-Up and Set-Down pots on the Y-SUS but not sure if Samsung have them. Tweaking Vs and Va helped as well.
On Samsung, it's likely to be Vs and Vsc pots. I'll try to attach a bulletin but it's Powerpoint, so who knows.
Dead right, quuq doesn't want to know about it, but Vs and Vsc is the recommendation. It's an ageing problem - like us, we don't have the zip we used to have. Another Logic board may also help.
Bruce