We have an 8560 desk phone that has a very dim display (so much so, the user cannot see who is calling).
However, adjusting the LCD contrast does nothing. In addition, it does not appear to be the device itself since moving it to another jack location produces a normally bright display.
Replacing the cord from the device to the wall jack does not resolve the issue. So, there's something up with the jack drop.
The device functions fine other than the dim display.
I'm wondering if anyone has run into this and if so, was it a power issue whereby the full power was not making it to the jack?
By the way, what is normal voltage at the device?

Assuming this is an IP phone, is there any chance the Ethernet switch PoE settings is limiting current to that particular port?

@grich, apologies, I didn't notice your response from the 23rd until now. No, it's actually a digital phone, not IP.
Something changed with that device. I traced wiring from the wall jack through the closet(s) and re-punched the 66-blocks just to be sure but no change yet. I may replace the wire on my next trip there. If still no success, then I may swap the extension with another address on the card to see if it makes a difference.