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Snowy Picture On Cable Input Only, OTA ok

Discussion in 'TiVo Help Center' started by naranja, Aug 5, 2012.

  1. Aug 5, 2012 #1 of 21
    naranja

    naranja Member

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    I have a Tivo HD that displays a snowy image only on cable channels. What you'd expect from a weak signal. I tested my cable connection with another identical Tivo and no problem so not a weak incoming signal. OTA channels are just fine. This is Time Warner analog cable no cable cards or tuning adapters. I'm guessing maybe a bad RF input? If so can it be replaced. Any ideas appreciated.
     
  2. Aug 5, 2012 #2 of 21
    dlfl

    dlfl Cranky old novice

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    Did you test the other TiVo with exactly the same cable connection that goes to the "bad" TiVo (i.e., not at another cable drop in the building)? That is the only way to be sure it's not a signal problem.

    I suppose it could be a bad power supply. Open it up and look for bulging or leaking capacitor cans. Power it up (WARNING: SHOCK HAZARD) and test the voltages where the Red, Yellow and White wires connect to solder pads on the PS board. Red-to-Black should be 5V +/-5%. Yellow-to-black should be 12V +/-10%.

    I'm assuming you mean snow (random noise) rather than blocky pixelation (?). The latter could be caused by a bad hard drive. If so, and
    you don't find a power supply problem then the problem is on the motherboard (e.g., tuner circuit) and is not fixable. I hope you don't have lifetime sub on it. You could buy another HD or upgrade to a current model TiVo. You will have to pay TiVo a hefty fee to get lifetime transfered to the replacement TiVo, if you had it. Remove the PS and Hard Drive from the current TiVo and keep them as spares or to sell. The PS will be useable only in another HD.
     
  3. Aug 5, 2012 #3 of 21
    naranja

    naranja Member

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    Jan 7, 2005
    Yes, tested with exatly the same cable connection after having issue in another room and yes, snow not pixelation. I'll check power supply, does it make sense that would affect cable and dont over the air picture? Same Question on tuner circuit, could that affect cable but not over the air picture? Thanks
     
  4. Aug 5, 2012 #4 of 21
    lillevig

    lillevig Hot in West Texas

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    It could still be a marginal cable signal with one Tivo having a more sensitive input than the other. Quick things to try: A different cable from the wall, a different wall outlet, an inexpensive power amplifier, a splitter. I know it sounds counter-intuitive to try a splitter since it lowers the signal level but maybe the signal level is actually too high for that Tivo.
     
  5. Aug 5, 2012 #5 of 21
    dlfl

    dlfl Cranky old novice

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    Since the cable coax and ota coax go into separate connectors on the TiVo, there must be some circuit elements that affect only the cable signal, and conceivably they might be more sensitive to incorrect voltage. Seems unlikely it's the power supply but it's good to check it anyway. At least that way you will know whether it's worth keeping as a spare part or to sell. New or reconditioned supplies for the HD sell for $100, see weaknees.com.
     
  6. Aug 5, 2012 #6 of 21
    naranja

    naranja Member

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    Jan 7, 2005
    I think I'll try a power amplifier but probably is circuits, might help even so? I did try it on different cable outlet with and without splitters. Thanks for the suggestions.
     
  7. Aug 6, 2012 #7 of 21
    unitron

    unitron Active Member

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    In the case of S2 and S3 TiVos, you should always suspect "capacitor plague" in the power supply just on GP, and eliminate it as a possibility.

    On the other hand, if it's TWC analog, you shouldn't trust it automatically, either.

    (what part of the country are you in?)

    See if you can test that HD's cable input elsewhere, with either a different tap from the same feed to your dwelling, or with a different source. Have you got an old VCR with a channel 3 or 4 output handy?
     
  8. Aug 6, 2012 #8 of 21
    dlfl

    dlfl Cranky old novice

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    Given that another TiVo HD performs well on the tap he/she is using, I'm not seeing the value of doing these tests.
     
  9. Aug 6, 2012 #9 of 21
    unitron

    unitron Active Member

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    When it comes to TWC, you can't even trust them to be bad consistently, and as lillevig indicated, another of the same model isn't going to be indentical in response down to the microVolt.

    If he gets even a moment of not-snowy on the cable input, then we can consider causes outside the TiVo.

    Although he still needs to check those power supply caps.
     
  10. naranja

    naranja Member

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    Jan 7, 2005
    Thanks for all the suggestions. Power supply looks ok. Signal booster no help. Must be in the mother board :(
     
  11. unitron

    unitron Active Member

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    Are you the owner of that identical TiVo that you mentioned?

    If not, does it belong to a really good friend?

    Try a temporary power supply swap, just to be sure that's not the problem

    There's a little, hard to see screw that goes into the top of the AC input jack from the outside, as well as the larger ones that go into standoffs on the inside.
     
  12. dlfl

    dlfl Cranky old novice

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    I agree. First it doesn't appear you've checked the voltages. Second, even if the (DC) voltages are in spec there could be noise (AC voltage) that could cause your problem. Detecting that is not so simple. You either need a scope or some very adroit voltmeter techniques.

    However I do think it's more likely that something has failed on the motherboard. It's just that based on experiences reported on this forum failures other than PS, HDD and fan are very rare.
     
  13. naranja

    naranja Member

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    Correct, I didn't check voltages. I looked again at the power supply and did see some bulging on the top of one of the smaller capacitors next to the outgoing wires. I'll try swapping power supplies. Is it likely at all that noise from the power supply would only affect the cable channels? I guess I'll find out. :) Thanks for all the expertise.

    Pic of capacitor (small upper left one):
     

    Attached Files:

  14. unitron

    unitron Active Member

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    Are you talking about the top one of the three smaller ones? The one right next to the two twisted red wires?
     
  15. naranja

    naranja Member

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    Jan 7, 2005
    Yes... but I just did the switch and no improvement. Must be the mother board. You never try you never know!
     
  16. unitron

    unitron Active Member

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    By switch I assume you mean power supply swap.

    Try it with the borrowed supply and the combo plug removed from the hard drive so that all you get is the Welcome screen and see if you still have the problem.

    (also check the caps on the borrowed supply, they're just as likely to be counterfeit/defective and need replacing soon)
     
  17. naranja

    naranja Member

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    Jan 7, 2005
    Yes, did the power supply swap to no avail. The borrowed supply looked completely different than the one in the defective machine but had no bulgers. I don't follow as to the welcome screen, it dispays fine in the defective box, it's only when I'm viewing a cable channel that I see snow. Thanks
     
  18. unitron

    unitron Active Member

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    Okay, I'm following your saga and this one

    http://www.tivocommunity.com/tivo-vb/showthread.php?t=490802

    as well and seem to have gotten my wires crossed a little.
     
  19. steve614

    steve614 what ru lookin at?

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    Are you sure it came from another TivoHD? It shouldn't look "completely different".

    Power supplies are not generally swappable between models.

    Look at this list and tell us which power supply most closely resembles the one you tried to swap in.

    http://www.weaknees.com/tivo-power-supply.php
     
  20. unitron

    unitron Active Member

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    You see how the S3 and the HD and HD XL supplies look very similar except for heat sink color?

    My HD supply looks like neither.
     

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