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Calling all tuner gurus!

Discussion in 'TiVo Series3 HDTV DVRs' started by unitron, Aug 11, 2013.

  1. unitron

    unitron Active Member

    Apr 28, 2006
    semi-coastal NC
    S3 HD (652)

    OTA and analog cable (TWC)

    No digital cable, no cable cards, no TA

    I guess this thing really has 4 tuners, 2 in the module that sticks out the back where it says antenna, and 2 in the (appears to be indentical) module that sticks out the back where it says cable.

    I can get two different OTA channels at a time with a decent antenna, but when I try for analog cable, only what it calls tuner 1 can get it, tuner 0 gives me the "searching for signal" excuse screen/overlay.

    It shows frequency shifting, by about 12 kHz, I guess as it tries to lock in something, or else it jumps frequency by more than that and modulation cycles though analog, QAM256, and QAM64.

    I swapped in the power supply from my other "both cable tuners work fine" S3 HD, and it doesn't make any difference.

    Naturally the one with the problem is the lifetimed one.

    Anybody got any ideas what the problem is?

    I've tried an inline attenuator in the co-ax feed, and tried it straight off the main feed before the splitters, and zilch, so I'm tentatively ruling out too hot or not hot enough a signal.

    I can get tuner 1 to do that same "seeking" frequency and modulation dance if I disconnect the cable and try to tune a cable channel, so maybe that's a clue.

    If I ever issue any terrorist demands, it'll be to force TiVo to release schematics. :D
  2. True Colors

    True Colors Member

    Oct 18, 2006
    So, long story short, you have a Tivo which is only able to record analog cable on one tuner instead of two tuners?

    I know that you dont want to hear this, but why are you trying so hard to keep going with analog cable in the first place? Most cable providers have already announced plans to get rid of it.

    Also, why not just pay a couple of bucks for the cable card and solve this problem that way?

  3. unitron

    unitron Active Member

    Apr 28, 2006
    semi-coastal NC
    If it (tuner 0) doesn't work on analog cable, what assurances do I have that it'll work on digital cable?

    And analog cable suits my current needs just fine, lets me continue to use several S2s as well as the tuners in several different TVs, and is less expensive and less complicated.
  4. dlfl

    dlfl Cranky old novice

    Jul 6, 2006
    Dayton OH
    I can think of a couple of reasons that would apply to me at least:

    1. No tuning adapter (failed tunes, missing channels, reboots required)
    2. No copy protection on all except local OTA channels.

    But then I'm on TWC.

    Actually I quickly got addicted to digital HD so that's what i'm running despite the above negatives.
  5. tenthplanet

    tenthplanet Member

    Mar 5, 2004
    Sounds like the signal is not going thru. I would check the signal path starting with the coax connector in the back and starting looking for a break, hopefully it won't be on a circuit board. The best option would be a tech with a signal generator and right equipment to trace the signal. You might just want to have Weak Knees have a look at it, especially if you want to hang on to the unit.
  6. L David Matheny

    L David Matheny Active Member

    Jan 29, 2011
    SE Ohio
    My guess is that it wouldn't. I thought there were only two tuners, each of which can tune using antenna channel mapping or cable channel mapping. Presumably each physical input is connected to a signal splitter, and each tuner is preceded by a signal selector which can connect to either the antenna splitter or the cable splitter.

    Your symptoms could be explained by a physical break in the link from the cable splitter to tuner 0 selector or by some type of failure in the tuner 0 selector or the tuner 0 configuration mechanism (affecting channel mapping). Try connecting an antenna signal to the cable input connector, preferably with at least one VHF channel available (since those map the same for antenna and cable), and see if the TiVo detects anything that way. If you could connect the unit to someone's digital cable feed, that would also be an interesting test.

    Most of this is guesswork, and I'm starting to get confused. But I assume you can always use more food for thought. Somebody may have to study some data sheets. Good luck.
  7. unitron

    unitron Active Member

    Apr 28, 2006
    semi-coastal NC
    The original S3 has two tuner modules on the motherboard.

    Each one has two inputs.

    The cable input on the back panel has a "Y" cable attached inside that runs to both tuners.

    Same for the antenna input.

    So each tuner module can receive either an OTA signal or a cable signal.

    The S3 HD, however, does it differently.

    There is one module with a single input sticking out the back where it says "cable", and another where it says "antenna", so apparently each tuner module has two tuners inside it, so that if one only used cable the other module would be unused and if one only used OTA the other other module would be unused.

    As I thought I mentioned previously, I can get 2 OTA channels no problem.

    I'm beginning to suspect that perhaps there's a phase-lock loop (PLL) chip (or section of a chip), which would be used to "lock in" on a particular channel's frequency, with stability problems, but before I consider a "transplant" from my non-lifetimed S3 (a soldering with a magnifying glass nightmare at best), I was hoping there might be someone here who'd dealt with the problem previously and had information which would help, or at least aid me in deciding what to do.

    (and I'd really like to not have half dissasembled electronics strung out all over the place for a change)

    What I have in mind for this machine is to be the "no monthly payments ever, so I can get hit by a bus and it keeps on working", "can still get the local channels if the cable goes out/gets too expensive" unit I could set up for my mom and transition her to it from the S2 DT I'm running for her now, because who knows when TWC will backstab us analog customers, the way the government did.
  8. Arcady

    Arcady Stargate Fan

    Oct 14, 2004
    Are you still grumbling about the demise of 8-track tapes, too?

    The cable system I am on has no analog channels. It also has no tuning adapters, because all that unwasted bandwidth allows them to run all of the digital and HD channels without resorting to SDV. The funny part is that it is TWC, but they bought it from a company that had already dumped analog, so they left it alone.

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