without knowing a thing about STV motherboards I can say this:
check google Images to see what kind of similarities/differences there are between the different versions if there are different versions of the board
if there are different versions
I would want to see if the connections are the same or different
power in/out in the same place
chip sizes and locations
capacitor locations, anything to tell me if it may or may not be possible
you might pull up totally different images which would make your decision for you without having to know squat about any of it
hopefully the different revisions are minor enough to be able to substitute one version with another
maybe one of these guys here knows exactly whats up but in lieu of that knowledge, I would start by comparing any images with what you have
you have checked you have +5volts dc going into the board and clean and tight grounds ??? last thing you want to do is to have a bad power supply and no matter what version you put in there, you would have the very same problem
check the +5volts on the power supply and ON THE BOARD
if you do have the correct +5volts ON THE BOARD then maybe there is a problem with the CPU good luck