[miro]

Hi Reiner,

It could be many resons for this problem. I'll start with the most commond problems first.

I.Electrical

 1. bad conection between flex PCB to mainboard

 2. bad conection flex PCB to LCD

 3. broken flex PCB traces - it is common problem in some lenses but probably not your problem, but it worts to check it.

 4. LCD module itself - e.g. backlight or interconection between lcd

 5. broken mainboard from previous LCD

II.optical

  as already mentioned by photonus

 

For electrical test you need at least on mulitimetter and it would be nice to have ociloscope. ectra care must be taken for ESD.