I went to Apple service provider yesterday with MBP and Thunderbolt display. I attached my Thunderbolt display and One TD from store to my Macbook Pro and both display seem to have same brightness - I forgot to test displays with different macs and same background.. 😟
However, when I came back home the picture of my TD was clearly brighter then a day before. So my guess was, that it needed to be off the electricity for some time.
On the evening the display shuts off again like it used to do before sometimes and when I managed to turn the picture back ON (few attempts of plugging it into electricity), it turned back ON, but the picture was darker again.
I left it OFF the electricity whole night and when I plugged it in, in the morning, the TD wouldn't want to show the picture at all. Every time I plugged it in, only some lines showed up for few seconds.
Then I tried it with other power cable (from my printer), and it started to working in full brightness in first attempt.
Can this be a problem of Thunderbolt displays - defected power cable?
It works fine today, for the whole day with power cord from printer. No disconnected disks too, ever.
I also just updated OS X to 10.9.4 - which showed up couple of minutes ago and the update included also this:
Improves the reliability of waking from sleep
🙂 Maybe this is the solution? Will keep you updated.