Altitude Posted February 22, 2013 Report Share Posted February 22, 2013 (edited) Thought I might post this since it may be useful to someone else: I have the green on black optrex displays on my sequencer that I have never been happy with since I could never really dial in a good balance between brightness and contrast and there were weird bright spots on the display as well. The backlight was always shining through too much at lower settings and it seemed that the only way to get it acceptable was to make everything super bright which I was not fond of. This was more prevalent over USB than running off the mains as well. I tried different pots with more resolution and although that helped, it didnt really resolve the issue. Fast forward a year or two and I used the same display on my Ambika, issue was not present there. That got me thinking to compare how those two circuits differ and the only difference was how the backlight was being powered. Ambika was just a resistor while the Core32 has the transistor current sink. The Optrex displays do not draw a lot of current at all so I just gambled and took out the BC337 and related stuff and just wired a 5K 20 turn trimmer between the - pin of the backlight and ground and viola! Works perfect now, background is nice and black and the weird bright spots are gone! I carefully checked the trimmer to make sure it could handle the current and no problems there.. Edited February 22, 2013 by Altitude Quote Link to comment Share on other sites More sharing options...
ilmenator Posted February 22, 2013 Report Share Posted February 22, 2013 Thanks for sharing this! Quote Link to comment Share on other sites More sharing options...
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