Hi,
I see there have no replies to this since August, but here's my two penny's worth.
I had the same problem with the tuner card vanishing from device manager.
I'd initially built my new HTPC in the office connect to a Dell 23" monitor via HDMI and a set of external speakers, via 3.5mm jack, and everything worked perfectly - install, update, shutdown, restart, sleep, anything - the card was always there and worked faultlessly
My problems started as soon as I'd decided everything was good to go and moved it to the living room. I connected it to the Sony LCD TV, via HDMI again, but with the audio over HDMI as well, instead of external speakers. and it worked to start with, but as soon as I shutdown the card vanished from device manager and restarting or warm or cold rebooting didn't help. The only way I was able to get it to reappear was to wipe the machine and reinstall Windows and start afresh. Then round we went as soon as the drivers for the card were installed and I restarted or shutdown (or indeed put the machine to sleep) the card would vanish.
The solution I found - well, so far it’s been all good for a week now, was to move the card to an alternate PCIe slot. In my case taking it out of the slot controlled by the chipset and into a slot controlled by the CPU.
Oh and, yes, I’d changed PCIe Link State Power Management to ‘Off’
Hope this might be of some help to someone out there.
Equipment used:
Gigabyte GA-Z97MX Gaming5
i5 4690T
TBS 6285 Quad Tuner
8GB (2x4GB) Corsair DDR3 Vengeance
Plextor M6e M.2 PCI-E 128GB
Pioneer BDC-207DBK DVD-R
Seagate ST4000VM000 4TB Video Hdd