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Suspected blown power

Discussion in 'TiVo Series 1 - UK' started by IcePee, Nov 17, 2014.

  1. IcePee

    IcePee New Member

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    Sep 30, 2007
    Hello,

    My Tivo won't boot. It won't even power on. There are no LEDs lit on the front. Leading up to the total power on issue I had these issues:

    1. I lost power to the home
    2. When I regained power, the Tivo was on, but live TV and latter recordings had no sound.
    3. Rebooted several times with no joy.
    4. Pulled the plug several times, with first time it booted, but on live TV, I got the blue screen.
    5. Second attempt, it's dead.

    Before paying for a new PSU, I want to test to see if it is providing power to the mainboard. I have a multimeter. Is that enough? Or, does the power need to be jumpered?

    The plug has 10 pins in 2 rows. Can someone let me know which pins I need to test?

    Thanks,

    IcePee
     
  2. spitfires

    spitfires wassock

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    Dec 19, 2006
    South Coast, UK
    Is the PSU completely dead? i.e. is the fan going round?

    Can you hear the disc(s) spin up?

    Do you still have your cachecard, if so then try removing it
     
  3. IcePee

    IcePee New Member

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    Sep 30, 2007
    Thanks for that, the tivo is completely dead, no fans, no nothing. Yes, I have a Cachecard, I've had it for over 3 years without much problems.
     
  4. spitfires

    spitfires wassock

    724
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    Dec 19, 2006
    South Coast, UK
    Ok sounds like the PSU is toast. Can you visually check it for blown capacitors. A blown capacitor will have rounded (convex) top, unlike a 'good' one which will be flat-topped.

    WARNING: do NOT touch the big cap unless Tivo has been off for an hour or so (a big cap holds its charge for quite a while and could give you a shock)

    Checked the fuse in the plug? (sorry, it happens ;) ). Is there a fuse in the PSU? (I can't remember)

    You could check the PSU hard disc connectors for +5v and +12v (red & yellow with respect to either black). (I think, from memory, the Tivo PSU should start up without needing a mobo attached)
     
  5. IcePee

    IcePee New Member

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    Sep 30, 2007
    Thanks, for that, I've attached the multimeter to the HD molex and didn't get any reading. Yes, there is a fuse in the plug and PSU, The PSU fuse wasn't blown, the continuity tester of the multimeter proved that. And I'm getting a current from the mains lead, so that's OK.

    It good to know that the PSU doesn't need a mobo to activate, as this is a complication I didn't need.
     
  6. sjp

    sjp Active Member

    1,722
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    Oct 22, 2001
    London, UK
    IP, are you anywhere near South London?
     
  7. spitfires

    spitfires wassock

    724
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    Dec 19, 2006
    South Coast, UK
    Ah, you were right, the PSU does need a mobo connected to power up. (I've just tested this on mine)

    With the mobo disconnected you should be able to hear a rapid ticking from the PSU. Very quiet but it's there if you listen in a quiet room with the lid off.

    I don't know which wire is the trigger but if you measure red wire to any black you should get around +3.2v (with mobo disconnected).
     
  8. nooneuknow

    nooneuknow TiVo User Since 2007

    3,554
    2
    Feb 5, 2011
    Cox Cable...
    Wrong, in context. The reason the power supply "ticks" when without a load is the power supply desperately trying to not self-destruct.

    This is NOT a proper diagnostic test, but an opportunity to completely blow a perfectly good power supply (or completely blow one that could have been saved). While the hard drive can be disconnected safely, the PSU should always be connected to the board, or a proper "dummy load", when powered.

    The usual 1-5 people can now come forward and say they haven't ever blown a power supply this way. That just makes them "lucky". The very conditions that lead to the ticking noise are the sounds of protection mechanisms struggling to cope.

    If you are unlucky: tick tick tick ... pow!
     
  9. IcePee

    IcePee New Member

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    Sep 30, 2007
    I live in London, but not south.
     
  10. IcePee

    IcePee New Member

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    Sep 30, 2007
    Thanks for this. So, you are saying that if I connect the PSU to the motherboard, but disconnect the HD molex, I should be able to test the molex connector for voltage?

    Would the molex connector be live if the motherboard was the faulty part?
     
  11. sjp

    sjp Active Member

    1,722
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    Oct 22, 2001
    London, UK
    if you fancy a trip to the bottom of the Northern Line let me know, you can have my, probably diskless, S1 - can't say I'm all that desperate to do the shipping thing so it would have to be a come'n'collect.
     
  12. unitron

    unitron Well-Known Member

    16,515
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    Apr 28, 2006
    semi-coastal NC
    The answer is, it depends.

    If the problem with the motherboard is such that it causes it to draw a lot more current than it's supposed to, that could possibly drag down the DC output voltages and give a mis-impression of the power supply's condition.

    But that's probably not the problem.

    (unless you see smoke or smell burning)

    Still I'd test it with the drive disconnected and the network adapter removed.

    But the power to the drive is not switched on or off by, or routed through, the motherboard.

    That would entail extra and unnecessary expense.

    So you should be able find +5V and +12V on the 4 hole Molex plug between red and black and between yellow and black (assuming the color coding is the same over there as here in the US).

    But like my fellow stateside geezer said, don't operate the power supply without it being plugged into the motherboard.
     
  13. unitron

    unitron Well-Known Member

    16,515
    25
    Apr 28, 2006
    semi-coastal NC
    You should probably hook the hard drive to a PC and run the drive maker's own diagnostic long test while you have the lid off the TiVo.

    Somewhere I've got handwritten notes on the US S1 power supply output plug.

    Take a look at the sticker wrapped around the big capacitor and tell me what output voltages and amperages it lists, so I can see if it's the same, in which case the motherboard plug pinout and wire color code is probably the same as well.
     
  14. IcePee

    IcePee New Member

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    Sep 30, 2007
    OK, so, I tried to power on, while the PSU was plugged into the motherboard, but the HDs were removed. I tested the molex and I got no power off it. So, that's it, the PSU is hosed.
     
  15. spitfires

    spitfires wassock

    724
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    Dec 19, 2006
    South Coast, UK
    Almost right; the ticking noise is the sound of the over-voltage regulator coping very well with the no-load condition. No ticking = not coping = blown fuse.

    These are pre "ATX standard" PSUs and are designed for always-on (i.e. no "standby mode") use - that's why they have over-voltage circuitry and an on-board fuse.

    Of course, I wouldn't recommend this with a known-to-be-working PSU but as IcePee's is likely toast anyway then it's a possible diagnostic.

    p.s. I can assure you that in the case of the UK Series 1, if you disconnect from the mobo then there will no voltage on the HDD Molex. That suggests to me that the power is switched by the mobo, at least in so far as the Molex's aren't powered until a load (the mobo fan?) is applied.
     
  16. spitfires

    spitfires wassock

    724
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    Dec 19, 2006
    South Coast, UK
    Did you inspect the capacitors? The 2200uF caps are the likely ones to blow. These aren't hard to replace if you have a soldering iron, and cost about 30p each.
     

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  17. nooneuknow

    nooneuknow TiVo User Since 2007

    3,554
    2
    Feb 5, 2011
    Cox Cable...
    I usually don't comment on anything older than a US TiVo HD power supply, as that is as far back as I have repaired for actual TiVos. I used to work in several capacities/positions, where power supply, both switch mode and linear, diagnostics and repair was a daily duty.

    I was trying to put things into layman terms, and prevent people from testing without a load on the molex connector.

    Your context correction is true. But, those who can make the distinction of what generation power supply they are working with, and what mechanisms is has or lacks, likely won't need any help from here, unless it's looking for a parts list and source.

    There's multiple mechanisms in most power supplies, which can create a ticking/strobing cycle condition. Loadless operation can stress components that typically never are even activated in normal operation, or once per power-up sequence. Catastrophic explosive failures of the primary chopping transistors can cascade through the whole power supply, depending on what conditions the failure creates.

    Even the most modern computer power supplies can blow, or give false readings, if the power-on sensing circuit is jumpered, without loading the outputs. Before ATX, without the sensing wire, some AT power supplies would blow if switched-on without a load, while others didn't. Some used internal ceramic resistors to insure a minimum load (greatly reducing efficiency when they had a load, which would be during 99.999% of the power-on time). My cache of ceramic resistors came mostly from scrapping those that had them.

    The quality of design often dictates what switch mode power supplies will live or die if powered-up loadless.

    Better safe than dead (power supply and/or the person messing around with it)...
     
  18. spitfires

    spitfires wassock

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    Dec 19, 2006
    South Coast, UK
    Good points, well made. I should've been more emphatic to say do not do this with a working PSU (I did it on a spare TiVo and was prepared for any consequences!), but I was trying to help the OP determine if the PSU in his UK S1 was really dead or not before he tries to find a replacement.

    He was trying to determine if the mobo was blown (less likely) or the psu (more likely). I still maintain a simple test in this case (for a S1 UK TiVo) is to disconnect the mobo and then switch on the psu for a brief few seconds. Ticking means the psu may be ok; no ticking means the psu is probably dead.

    This is, of course, only applicable to UK S1 TiVos (this is a 'Series 1 UK' forum ;) ), and I have no knowledge about other TiVos. So, as nooneuknow points out, do NOT do this with other TiVo models.


    Indeed.
     
  19. IcePee

    IcePee New Member

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    Sep 30, 2007
    I tested all the capacitors with an multimeter. They all look OK. In frustration, I just bought a new PSU. Well, it's arrived and now my Tivo is powered on and booted. I think job's a good 'un.
     
  20. spitfires

    spitfires wassock

    724
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    Dec 19, 2006
    South Coast, UK
    :up: Cool, glad it's working ok. Gotta keep these old guys going :)
     

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