DIYbanter - Need ID on SMT component

Hi All,
I am trying to repair a monitor from a CNC machine control console. It
is a 14" monochrome VGA monitor. The board is relativly simple,(only 1
IC, a V sweep generator, all the rest of the components are discreet)
and I have HV sweep, etc. The video comes in on the "Green" line, and
is fairly easy to trace through the circuit. I am losing the video
signal at the one-and-only SMT component on the entire board. It just
figures. Anyhow, the component is an SOT143, 4 lead package. I examined
it under magnification, and the only marking on the part is;
"MA" followed by a "P" (printed in smaller font) and maybe the numbers
4 and 5 printed in much smaller print and rotated 90 degrees from the
other letters. I am not 100% certain of the 4 and 5, they are very
faint. Any idea what this may be and how I replace it? Even If I could
simply discern its function, I would not be above hacking some
equivelent component in.

This is from a custom built assembly machine. The people who made it
are no longer available to help.
Any advice/Ideas!

Thanks in advance,
AL