This works for my WD-52628 which I got in October 2005.

Just put the Mitsu remote in direct mode: Hold the power key and press 090

Don't forget to put the Mitsu remote back to normal: Hold the power key and press 000.

Device and then
1 = input 1 (S-video/ composite)
2 = input 2
3 = input 3
4 = HDMI 2
5 = Component 1
6 = Component 2
SQV = HDMI 1
PIP CH up = Ant 1
PIP CH down = Ant 2

Power = Power on
stop = Power off
Pause = AV Reset

You can now teach your universal remote the discrete codes using the learn function.