Welcome to the forum!
Here is the latest firmware update for you LN52A750 (US Version).
There are also instructions at that link, and it will walk you through the process. If you haven't ever updated the firmware, the latest one will have all the updates from the prior ones.
Let me know if you have any questions.
I have the model LN52A750 RIFXZA for 3 weeks and have lost picture Quality, and was on this site and came across where I could look up the version of firmware, went through the steps to for version, and was informed that.
FIRMWARE CAN BE UPGRADED
but still don't know what firmware should be upgrade to what version