I’m building up a yellow magic board with parts. I ordered everything from digikey thing on the digital display board works except the lcd screen glows blue with no characters at all. I’m build a second digital display board and the same problem comes up. The leds and switches appear to be working fine. Some noise comes out when the board is plugged into an amp but it’s high pitched and only changes slightly. Any help would be appreciated.
Did you remember to tweak the contrast trimmer? You are describing the classic symptom of not setting the contrast.
As for the noise, the best start would probably be to review all your soldering carefully. I speak from the experience of having left a few pins on a chip unsoldered completely, but there are loads of variations of getting this wrong, generally cold solder joints or solder bridges (inadvertent connections). Seems that actually frying parts is a pretty rare experience though!