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Thread: 2nd tuner has bad reception issues on DirecTV TIVO Series 2

  1. #1
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    2nd tuner has bad reception issues on DirecTV TIVO Series 2

    2nd tuner has bad reception issues on DirecTV TIVO Series 2. Already determined it's not the cables, etc. (swapping cables- problem does not follow) I've read all over that it could be the power supply. However, I've replaced two caps (16v 2200mf ones) and still have same problem. Before I start on another board with the same problem, I thought I would ask to see if it is a cap problem or something else. Thanks

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    Quote Originally Posted by tadtv View Post
    2nd tuner has bad reception issues on DirecTV TIVO Series 2. Already determined it's not the cables, etc. (swapping cables- problem does not follow) I've read all over that it could be the power supply. However, I've replaced two caps (16v 2200mf ones) and still have same problem. Before I start on another board with the same problem, I thought I would ask to see if it is a cap problem or something else. Thanks
    Were those caps on the +5V output or the +12V?
    Too busy TiVo wrangling to watch television anymore.

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    How do I tell where to measure the voltage outputs?

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    Quote Originally Posted by tadtv View Post
    How do I tell where to measure the voltage outputs?
    You're starting to scare me.

    Did you replace the capacitors yourself?
    Too busy TiVo wrangling to watch television anymore.

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    Yes I did. And I think my question is valid. Do I check off the hard drive cable-which colors, the ribbon cable- which points, the under side of the circuit board? There are a lot of different points you can get varied voltages. What voltages am I supposed to be getting? I guess if I knew more, I wouldn't be asking for help.

  6. #6
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    Okay, when you put in the new (I hope you used high-temp, low ESR) capacitors, the hole where you put the negative lead is in a "sea" of copper (although it's actually called a "land") on the underside of the board and all of the black wires should also be connected to that same expanse of copper. The positive lead, assuming we're talking about one of the usual suspects, should have been connected to the same land as either the red wire(s), the +5V output, or the yellow wire(s), the +12V output.

    So you can stick the meter's black lead metal tip into one of the black wire-containing holes in the plug that goes to the motherboard (jam it in good so it stays 'til you pull it out), and then put the red lead tip in the hole with the red to measure the +5V level and the hole with the yellow to measure the +12V level.

    Start with the TiVo unplugged from the wall socket (best way is to have it plugged into an outlet strip with a switch you can get to easily), always knowing where both ends of the power cord are, keep away from the end of the TiVo with the power supply, jam the meter's black lead into one of the black wire holes (or if you have an alligator clip on the end, ground it to the metal chassis away from the power supply), have the hard drive disconnected, connect the TiVo to power, and check the red wire and the yellow wire. Also check the orange wire, which should be +3.3V, and, depending on which model TiVo, there may be a wire with around +30V which the tuners use for deriving a tuning voltage, and on the original S3 there's a wire at 8 or 9V that feeds the front panel separately from the ribbon cable that connects the regular LEDs and the InfraRed module.

    Be sure that ribbon cable is fully and properly seated where it connects to the motherboard before powering up the TiVo.

    There should either be something silk-screened on the power supply board or a sticker wrapped around the big fat capacitor that says what the different output voltages are supposed to be.

    Make note of your voltage readings, power down the TiVo, connect the hard drive, and power back up and take your readings again and make a note of them.

    There should be little if any difference.

    Report back with the figures you get.
    Too busy TiVo wrangling to watch television anymore.

  7. #7
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    Thanks for the details. With both of the supplies I have, I only have the hard drive power cable (4 conductors) and a 20 pin ribbon cable. I don't see any orange wire. Also, with the Hard drive connected, how can I still measure the voltages on that connector- OH I JUST saw a remove plastic top that comes off. Okay so what about this orange wire? The power supply is a AcBel ap12st01 REV B. The caps are high temp 105c but I just looked at the data sheet and can't determine what a ESR rating is? Here is the link to the data sheet.
    http://www.nteinc.com/capacitor_web/pdf/vht.pdf

  8. #8
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    Sorry, thinking about power supplies from different models.

    If there's something wrong with the power supply, it'll most likely reveal itself as a problem on the +5V and/or the+12V outputs, which can be measured at the hard drive Molex plug.

    If it can't do the job, the reading with the drive attached will probably be lower than with it not attached.


    Anyway, find where the + lead from the capacitors you installed goes through the power supply circuit board and see if the red wire or the yellow wire connects to that same area of copper on the bottom of the board.
    Too busy TiVo wrangling to watch television anymore.

  9. #9
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    In my case, it looks like design flaw in unit leads to eventual 2nd tuner failure. I read through a bunch of posts concerning this and managed to mitigate most of it by bridging the 2nd tuner chip with a capacitor. Are you using Svideo connection?

    Smee

  10. #10
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    A few comments on this.

    1. NTE does not sell low ESR capacitors. I recommend Panasonic FM series from Digi-Key. Specify USPS first class mail shipping. They also have Nichicon, United Chemicon, and Rubycon caps that are excellent.

    2. I have had similar problems with Series 2 DirecTiVos (since removed from service). The symptoms do indicate excessive ripple on the power rails. This is usually not identifiable with a DMM. In one memorable case this was due to bad SMD electrolytic caps.

    3. Fixing the problem bridging the power inputs on the tuner chip with appropriate caps would definitely indicate the problem is excessive ripple on the power rails.

    PlainBill
    There's a difference between needing help, and just being plain ole' lazy.

    "You cannot teach a man anything. You can only help him find it for himself." Galileo Galilei (1564-1642)

    HR20-700 with 2 TB, HR22-100, HR22-100, HR22-100, HR23-100 all running 0x5cd and networked.

  11. #11
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    If you're in or near Raleigh, there's a reliable source I've dealt with by mail.

    Search Craigslist for "low esr"

    Tell him unitron sent you.
    Too busy TiVo wrangling to watch television anymore.

  12. #12
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    I haven't had a chance to measure the voltages yet. But as far as the NTE caps I put in, should I put others in. would it make a difference now. Also I'm not using the s-video output. I did a few years back before HD but pulled it after reading about the s-video/tuner relation a few years ago. Bridging the tuner chip seems daunting to me.

  13. #13
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    Quote Originally Posted by tadtv View Post
    I haven't had a chance to measure the voltages yet. But as far as the NTE caps I put in, should I put others in. would it make a difference now. Also I'm not using the s-video output. I did a few years back before HD but pulled it after reading about the s-video/tuner relation a few years ago. Bridging the tuner chip seems daunting to me.
    I'd replace the caps AFTER you got the second tuner issue resolved - or order all the caps at the same time.

    I'd like to see the posts Smee mentions before going out on a limb, but the tuner chips are CX24109-11, U2000 (tuner 1) and U2001 (tuner 2). A VERY quick glance at the datasheet indicates it uses a single 5V supply. VR5 and VR6 are 8M05 5 volt regulators next to the tuner chips. A quick check with a DMM (measure the resistance between the output of VR6 and the Vcc pins of U2001) would verify they regulate the supply voltages. If that checks out, the easy way would be to solder a 220F low ESR cap between the output and ground pins of VR6.

    The caps in the area are electrolytics in an SMD package; these are more prone to failure than thru hole types.

    PlainBill
    Last edited by PlainBill; 08-11-2012 at 08:02 AM. Reason: Correct typo
    There's a difference between needing help, and just being plain ole' lazy.

    "You cannot teach a man anything. You can only help him find it for himself." Galileo Galilei (1564-1642)

    HR20-700 with 2 TB, HR22-100, HR22-100, HR22-100, HR23-100 all running 0x5cd and networked.

  14. #14
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    Quote Originally Posted by PlainBill View Post
    I'd replace the caps AFTER you got the second tuner issue resolved - or order all the caps at the same time.

    I'd like to see the posts Smee mentions before going out on a limb, but the tuner chips are CX24109-11, U2000 (tuner 1) and U2001 (tuner 2). A VERY quick glance at the datasheet indicates it uses a single 5V supply. VR5 and VR6 are 8M05 5 volt regulators next to the tuner chips. A quick check with a DMM (measure the resistance between the output of VR6 and the Vcc pins of U2001) would verify they regulate the supply voltages. If that checks out, the easy way would be to solder a 220F low ESR cap between the output and ground pins of VR6.

    The caps in the area are electrolytics in an SMD package; these are more prone to failure than thru hole types.

    PlainBill
    It is Post 102 on TC: Click Here

    Further down that chain there are some picture folks have taken. I haven't had any issues with pixelation on tuner 2 since I modded my units. I put in a 470 uf 25v capacitor on U49, Pins 3 & 7 I grabbed from a spare power supply. Now I have another unit with a failing power supply. Grrrr.....

    Smee
    Last edited by PlainBill; 08-11-2012 at 08:03 AM. Reason: Correct typo in original post

  15. #15
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    Quote Originally Posted by Smee View Post
    It is Post 102 on TC: Click Here

    Further down that chain there are some picture folks have taken. I haven't had any issues with pixelation on tuner 2 since I modded my units. I put in a 470 uf 25v capacitor on U49, Pins 3 & 7 I grabbed from a spare power supply. Now I have another unit with a failing power supply. Grrrr.....

    Smee
    Thanks for the information. I've located U49, but have been unable to read the part number on the little bugger. That definitely sounds like on of the surface mount electrolytics in the area has failed.

    PlainBill
    There's a difference between needing help, and just being plain ole' lazy.

    "You cannot teach a man anything. You can only help him find it for himself." Galileo Galilei (1564-1642)

    HR20-700 with 2 TB, HR22-100, HR22-100, HR22-100, HR23-100 all running 0x5cd and networked.

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