Mac Mini Thunderbolt Display Instability 10.10.5

Thanks woodmeister50. I tried your tip (disregarded the Thunderbolt Display's built-in cable and connected to my Mac Mini using a standard thunderbolt cable). The result appears to be a stable system. I then did a full power down and reverted back to my standard setup:

1) Thunderbolt Display connected to Mac Mini using built-in cable.

2) External WD Thunderbolt Drive connected to Display with separate thunderbolt cable.

Logic would dictate that the problems should return. But they haven't. I normally incur the external drive disconnecting, followed by the screen problems within 10 minutes of boot. If the external drive is not connected, the screen problems similarly appear within 10 minutes.

Swapping cables around and disconnecting semi-permanent USB devices does seem to my improve system stability. It does seem to suggest that software conflicts are being cleared as a by-product of the power-downs and swapped/released connectivity.

I obviously now need to re-establish my USB devices and run for a few days. I will report back.

Interim update ...

My system has now now been completely stable for 24 hours. The Thunderbolt Display's built-in cable has been connected back into Mac Mini directly and all USB devices are re-connected. The system boots cleanly, quickly and there are no display issues whatsoever.

The only omitted connectivity is my external storage, a Western Digital Thunderbolt Duo 8TB. This was connected to the display's additional port via a thunderbolt cable. Logic would suggest the problem therefore lies with the additional port on the display, the cable or the 8TB drive's logic board (the WD utilities did not report any disk issues before I disconnected it).

Given that it worked intermittently, I strongly suspect the cable is the problem and am going to purchase a replacement at my local Apple Store before re-introducing the drive to my rig. Once again, I will report back.

Interim update 2 ...

Ok I have the resolution to my display flicker and sleep/wake problems. It appears I was not doing the correct SMC reset for my edition of Mac Mini. The 2011 model requires a power disconnect, followed by holding down the power button for 5 seconds. I unfortunately executed the first set of instructions I came across and they were not correct. I had not appreciated there are different actions depending on your specific Mac model and its release date.

The external WD Thunderbolt issues persist however. Re-introduction of the external drive to my rig using the Display's thunderbolt port (and NEW Apple cable - £35 yuk!) still produces the same problems: drive disconnects after a few minutes of use followed by screen flickers. The SMC reset described above returns stability after I've disconnected the drive. Cabling is therefore not the problem.

The Thunderbolt Display's port seems an unlikely candidate. It works fine for video with both cables I now have at my disposal. I am starting to detest my investment in Thunderbolt, more so that I have important data on this drive since my last Time Machine. Next steps:

1) Run the Mac Mini with an HDMI monitor.

2) Connect the external drive to the Mac Mini thunderbolt directly

3) Hopefully achieve enough stability to rescue data from drive

Onwards and downwards. Update 3 to follow.

*** SOLVED ***

Ok with the trial and error above and a lot of tips from the folks over at Yosemite ejects external drives I've managed to achieve stability.

Rig is Mac Mini 2011 / Thunderbolt Display / Westen Digital Thunderbolt Duo (daisy-chained to Display's additional TB port).

My steps to enlightenment have been as follows:

1. Perform SMC reset specific to your Mac.

2. Shutdown and disconnect Mac / Display from wall power.

3. Disconnect all peripheral connections except TB video cable.

4. Connect wall power. Boot Mac. Wait 10+ seconds before logging in.

*** Your system should now be free of display flicker issues caused by external HD instability ***

5. Shutdown cleanly and disconnect Mac / Display from wall power.

6. Disconnect video cable.

7. Connect TB drive cable to TB Display & Storage Unit. Attach Storage Unit power.

8. Connect wall power. Boot Mac. After chime, connect video cable.

9. Wait 10 seconds before logging in.

*** Your should now be able to see external HD attached (in my case) via Thunderbolt cable ***

10. Access System Preferences -> Energy Saver. Set both slider controls to ‘Never’.

11. Access System Preferences -> Spotlight -> Privacy. Deny access between Spotlight and External Storage.

12. Rescue External Storage content (if applicable).

13. Remove Western Digital Drive Management Software from Applications.

14. Format External Drive / creat new RAID set using OSX Disk Utility.

15. Shutdown cleanly. Boot Mac.

16. Access System Preferences -> Energy Saver. Reset defaults.

17. Access System Preferences -> Spotlight -> Privacy. Deny access between Spotlight and new external HD Label created in Step 14.

*** Stability returned to rig ***

Thank you to all for support and encouragement. I hope these steps help if you have a similar issue.

Thank you to those who got in touch about Step 16. Should read:

16. Access System Preferences -> Energy Saver. Reset defaults. Untick "Put Hard Drives to sleep when possible"

This resolves loss of USB/TB drives in Mac's which have sleep capability.

Moving contribution over to Yosemite ejects external drives.

Root cause of Thunderbolt display instability 100% a by-product of external drive eject(s) connected via its thunderbolt port.

Problem nothing to do with display itself.