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634 backlight doesn't get brighter than 50%


New member
I've had my serial 634 for a few weeks and when first installed the backlight was fine. You slide the slider to zero, no backlight, to 100% nice and bright. Lately I noticed it was dim so I went to the slider, it was still at the 80% I had set it, but in sliding and looking at the brightness, the backlight doesn't seem to get any brighter once the slider hits about 50%. Needless to say in a well lit room and even with some contrast it's difficult to read.

The light is even across the unit and is the correct color, it's just not as bright as it used to be.

I've double checked my connections and voltages and they are fine. Any ideas?
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New member
I'm using CrystalControl but also tried WinTest since the sliders change contrast and brightness in real time. In moving the sliders, you see the backlight getting brighter and dimmer, but it's barely noticable which is probably why I though CrystalControl wasn't doing anything above 50%. And the brightness with either is NOTHING like when I got the unit. Then it was very bright at the highest setting (like the pics on the site) but now it's hardly readable at the highest setting.

The unit functions perfectly with the exception of the backlight issue, and even then, the backlight works, but it's like it's not getting the necessary voltage. I check the connector it's on, and it's a steady 5.04V.
USB LCD Displays - Graphic and Character LCDs with a Keypad