I have been getting the "black screen" during playback of recorded programmes. Rewinding the offending section plays perfectly. In some cases, another programme was being recorded at the same time.
I was wondering if there was local (in my vicinity) impulse interference that might cause the processor to go off and do some other vital operation, thus freezing the playback. Some of the recent Dr Who episodes have had the "No Signal or Scrambled" message every six to ten minutes. Signal was 100% quality, and 70% strength, using an external aerial that came out the Ark, by the look of it. The box is an un-modified T2, with 1Tb disk, filled to 2/3 capacity, firmware is of the official broadcast "29" variant. When it does the "black screen" on playback, I have noticed furious disk seeking noises. Fan seems to kick in and out as unit temperature rises and falls, as normal. Also noticed excessive case vibration a few days ago.
I decided to fit a X-Beam loft aerial, with modern screened coaxial cable. Signal strength jumped to 81% on the PSB Muxes. Was still getting the "No signal" message.
Still annoyed by the black screen, I presumed that a poor connection was to blame. I removed the lid, unseated and reseated the disk connectors, tightened the fan mounting screws a little, wiped dust off the processor heat-sink and put the unit back together again. Vibration now seems to be cured; that plastic disk shroud is a damn nuisance.
The same day, I fitted a booster box, which increased the signal strength to 94% (quality still 100%). It is too early to report my findings.