Mpc 4000 wont boot

Ok.. So i just got a faulty 4000, it booted up but had no input or output signal.. Stupidly curious i opened the mpc to see if there was any visual faults.

I unplugged a few cables and boards, took the efx and ram out then put them back. Everything was put back exactly as i found it. Nothing was broken or loose.

However, when i turned my mpc on again it wouldnt boot and is now stuck on a blank screen..

Any suggestions?

Thanks

Ok so it looks like it boots but the the screen is blank (but turned on) all the buttons work and light up when pressed, can hear the hard drive working.

The screens ribbon cable is plugged in and turns on but it just wont show anything

Maybe the contrast pot is broken - does it make any difference when you adjust it? if not, check it with a meter.

Also check the ribbon cables again, make sure they haven't got damaged when screwing the case together.