Measure the -5V supply rail. It could be low because the RS232 level shifter chip has faults. Also check the +5V and -5V at the LCD itself to rule out a connection issue (bad joint at connector or leading to connector).
Jeff Birt -----Original Message----- From: M100 <[email protected]> On Behalf Of ExPLIT | Pawel Radomychelski Sent: Friday, April 16, 2021 2:20 PM To: [email protected] Subject: [M100] NEC PC-8201 adjusting contrast doesnt work Hello collegues. I got an Japanese NEC PC-8201. While its working, i can't adjust lcd contrast. I tried already change lcd and power board, but it didnt help. Problem is somewhere on the mainboard. I removed the round black part for ajusting lcd contrast, cleaned it and put back on. Didn't help. Sometimes i see also small flimmering, lcd is getting a bit darker and than back to normal. Did somebody had the same issue? Thanks -- Kind regards / Mit freundlichen Grüßen ExPLIT IT Soltions Pawel Radomychelski
