I did the following in October 2011 on my Samsung UE40C6700 with the firmware T-VALDEUC 3004.0.
The following was taken from http://wiki.samygo.tv/index.php5?title=Enabling_the_PVR_for_C-Series&oldid=1807
The following typografical conventions apply in the following: buttons to press on the remote are written in bold, menu items that appear on the TV are written in monospaced font.
Be very careful what you press on the remote whilst in service menu. Move through menu list by pressing down or up arrow only. Only press right arrow to change an option.
NOTE: All user settings (and TV channels) will be reset to default after this so write all your settings down on paper and reset them afterwards.
BE CAREFUL IN THE SERVICE MENU!
HOTEL MODE to ON (right arrow) and then turn off TV.Control and select this (right arrow) - new menu appears (S2) - move down to Hotel Option and select this (right arrow) - new menu appears (S3) - move down to Clone TV to USB and select this (right arrow). TV then checks USB. - Wait until the message Completed Successfully appears. - Select OK by pressing enter.Sub Option category and select (right arrow).PVR Support and set to ON (right arrow). (Move to PVR by pressing down button, not right!!!) This option now appears on its own on the TV screen, press return to go back to main menu again (S5)Gemstar Support to ON if required for the GuidePlus EPG.RS232-Jack to Debug (this is a safety measure)Watchdog to OFF (this is a safety measure)Hotel Option and select this (right arrow). H1 menu appears then set Hotel Mode to OFF (right arrow) and power off your TV.If you now press record or pause whilst watching live TV the TV will ask to format the USB drive. If this is done successfully the PVR function should now work and you enter timeshift mode and begin to record to the USB.