The screen was working okay and displaying characters properly when I got it. The EL backlight was burned out and yep could hear the high pitch squeal of the inverter that everyone mentions. Hopefully the replacements have a modern LED backlight that does not require high voltage and can just draw from the normal 5V or 12V that is usually floating around. This guy has some replacement screens http://www.ebay.com/itm/BACKLIGHT-LUZ-DE-PANTALLA-O1W-o1w-K2000-MPC-K5-i3-T3-A80-more-NEW-LOWER-PRICE/271057465604?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649
and I have bought from them before to repair my MC505 no problemo. I would look to something like that as I was eventually planning on getting rid of the inverter board and the noise as it was not necessary for operation. Thankfully this is a model that is dotmatrix vs proprietary LCD chars so there are options. I would have to look to see if it is serial or parallel but guessing it is parallel due to age of the unit. I would be happy to test out your replacement screen for you, I just hope it would not be cost/time prohibitive to you and your K5. If I am misunderstanding something or if I can help with your screen let me know :)