Jamma Cabinet - NeoGeo and PC with MAME inside. Monitor dying - help!

[andyward82]

Hello. I've got a mega old Jamma cabinet with a NeoGeo Puzzle Bobble cart wired to it, but can also plug a PC into it and play MAME games. The monitor has been slowly losing quality over the past few months and now it's VERY poor. When the PC screen comes up to play MAME games the top blue bar (which is dark 'royal' blue in real life) is actually really light very much like this icon ( ) but lighter. The rest of the screen is a bit 'off white'.

I don't know anything about monitors but because RGB gets brighter as you add colours to it I'm thinking one of the things that puts one of those colours onto the screen has died.

Does anyone have any ideas on how I can diagnose this properly and then subsequently fix it?

It may be worth adding that it's not just the PC playing MAME that has this problem, it's also on Puzzle Bobble but seemingly not remotely as bad....