I've been experiencing difficulties with my TiVo XL4 and am hoping a fresh set of eyes will help me find a solution.
The problem began a few weeks ago, when I began to have problems with my TiVo XL4 on my 2nd floor. Pictures were blocky and upon checking the signal strength, I saw a reading of 70% with 38 SNR. This is excellent SNR, but a low signal strength. I have a TiVo Premiere on my 3rd floor, which has 90%+ signal strength, so the fact that the 2nd floor TiVo had worse signal strength was strange.
A Comcast technician and I ran a line directly from the point of entry into the house to the TiVo XL4 on the 2nd floor. However, the signal strength reading was still ~70%. I brought down the TiVo Premiere from my 3rd floor and plugged it in and discovered it read over 90%+ signal strength!
I now assumed the problem was either the cable cards or the tuners built into the TiVo. I swapped the cable cards between them. The 3rd floor Premiere maintained its 90%+ signal strength, while the 2nd floor XL4 lost all signal and was no longer able to connect at all (modulation for all channels which I attempted to tune to switched back and forth between QAM 64 and QAM 256). A Comcast technician returned and swapped cable cards for the XL4 but the signal never returned. At this point, I assumed a bad tuner and got TiVo to send me a replacement XL4.
The replacement XL4 arrived. I installed a cable card into it, but it showed the same problem the previous XL4 did -- switching back and forth between QAM 64 and QAM 256 and was unable to tune to any channel. I again swapped cable cards with my working TiVo Premiere and reactivated both. My TiVo Premiere works fine, the XL4 still does not. At this point, I still can't find any reason to suspect the cable cards -- the XL4 even shows the cable card as activated through the pairing page.
I attempt to connect the replacement TiVo XL4 via a direct line run by me and the Comcast technician to the basement point of entry and it is unable to tune. I also carry the TiVo down and directly plug it in to the basement point of entry, and it remains unable to tune. Finally, I decide to bring the replacement XL4 up to the 3rd floor and plug it in. Amazingly, it is able to tune to all channels. Signal strength hovers around 70%, but it can tune and there is no blockyness.
So to make a clear rundown of where the XL4 works:
- WORKS: Connecting an Tivo XL4 to a 3rd floor coax output, behind the unity amplifier Comcast installed, which then shows 70% signal strength
- DOESN'T WORK: Connecting the TiVo XL4 to the 2nd floor coax output, which then connects through the wall to the unity amplifier in the basement Comcast installed
- DOESN'T WORK: Connecting the TiVo XL4 to a direct line run through the hallways to the unity amplifier in the basement Comcast installed
- DOESN'T WORK: Connecting the TiVo XL4 DIRECTLY to the house's coax point of entry (no amplifiers, etc.)
This doesn't make sense. Connecting the TiVo XL4 to the PoE in the basement doesn't work, but connecting the TiVo XL4 to the 3rd floor bedroom works. How can this be possible?
My best guess is that the signal is too "hot" (amplitude too high) for the TiVo XL4 to work at the PoE. Bringing it all the way up to the 3rd floor, which goes through some RG59 runs, lowers the signal strength enough for the unit to be able to tune properly (although the 70% signal strength it receives there remains a mystery, as the Premiere installed in the 3rd floor gets 90%+ signal strength)
I checked my cable modem and the downstream signal level doesn't seem very high (3 dBmv), so I'm not sure how likely it is that the TiVo XL4 is actually receiving a signal too hot for it. But at the moment, too "hot" of a signal is the only thing I have to work with.
Any ideas? Thanks for reading my long post =)