Very Dim Screen on Touch

[agbagb]

I fired up my spare Touch to do a Community Firmware update. For a moment, the screen was "normal" and then it went very, very dim. Just about readable, in a very dark room..... Very, very difficult though to enter a new network password accurately!

I've tried it with different "known good" power supplies, to no effect. I can just about read the screen to navigate to the Manual Brightness setting, but even with that on full, the screen is still very dim. Everything else about it seems to work fine.

Any ideas?