Sky HD box tuner woes

[cynic99]

The tuners (both) in my Sky HD box have been losing channels. Some channels work fine with very high signal strength (I'm using 90cm dish), while other channels are "iffy" - no signal one minute, then strong signal for half an hour or so, then drop-out again. The situation has gradually become worse over the past year or so, with more & more channels dropping out for longer periods of time. It's now got to the stage where it doesn't even get the transponder to do a scan after full power cycle bootup. Swapping either of the LNB inputs over to my Dreambox 500S brings up perfect signals on all freeview channels at excellent strength - so I know the problem is not with the dish/LNB. My LNB meter shows the Sky HD box is toggling the H/V and 22KHz OK.

My thinking is that maybe a PLL oscillator in the box has drifted and not locking - but *both* tuners? I haven't opened the box for a look-see yet (I'm hoping maybe accumulated dust on some stripline oscillators), but thought I'd ask on here in case anyone has experienced a similar problem.

Thanks for reading

[modify]

There has been some tuner failures I understand so im told , so you may have a hardware issue .
Make sure that you dont have your LNB cross nulled incorrectly .
Watch out for box lnb fighting ...as in , a dreambox that is getting a split feed of the skybox ...and if its not setup correctly , may be sending 22khz signals or voltage switching that could confuse the LNB whats to be done by its internal service scanning.
Just a thought ...prob a hardware fault tho I think ..esp if nothing else has been changed . If you have a feedhorn that has no cover on it , its probably a spider ...very common problem with open feeds . Also , water ingress on the connection outside - check it aswell . hope this gives you a few things to cross off the list . Cheers