Mpc3000 contract button doesn’t make any difference

Hi everyone,

I’ve just replaced the backlight for my mpc3000, the brightness is exactly the same as before. However I did notice that the contrast button does make changes when I turn the knob, however no difference when I push the button on and off.

I can still see the letters, however the bright blue light isn’t as prevalent as before.

Can anyone please let me know why this happening?