Broken (?) CPU module - SUN

This is a discussion on Broken (?) CPU module - SUN ; I got a 450MHz CPU (501-5339) for my U60 in the mail today. Installed it, powered the machine up, everything seemed fine. When I went to set the machine back upright I heard a rattle, like a screw had fallen ...

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  1. Broken (?) CPU module

    I got a 450MHz CPU (501-5339) for my U60 in the mail today.
    Installed it, powered the machine up, everything seemed fine.
    When I went to set the machine back upright I heard a rattle,
    like a screw had fallen into the case. I took out the CPU
    module and two surface-mount capacitors fell out of the module!
    There are in total three capacitors missing from the
    left-hand side of the top side of the board, right above the
    connectors.

    Out of curiosity, and figuring it would've toasted the board
    already if it were going to, I plugged it back in and booted
    the machine up -- no complaints. I ran SunVTS's cpu tests for
    about an hour and the module passed them.

    I know I should probably try and return the module and (sigh)
    start looking for another one, but I was interested if anybody
    knew anything about what those capacitors do? Why does the board
    still work?

    This is the second CPU I've gotten with capacitors broken off.
    I don't whether that's Sun's fault or the USPS's...

    Bill

  2. Re: Broken (?) CPU module

    Bill Green wrote:
    > I got a 450MHz CPU (501-5339) for my U60 in the mail today.
    > Installed it, powered the machine up, everything seemed fine.
    > When I went to set the machine back upright I heard a rattle,
    > like a screw had fallen into the case. I took out the CPU
    > module and two surface-mount capacitors fell out of the module!
    > There are in total three capacitors missing from the
    > left-hand side of the top side of the board, right above the
    > connectors.
    >
    > Out of curiosity, and figuring it would've toasted the board
    > already if it were going to, I plugged it back in and booted
    > the machine up -- no complaints. I ran SunVTS's cpu tests for
    > about an hour and the module passed them.
    >
    > I know I should probably try and return the module and (sigh)
    > start looking for another one, but I was interested if anybody
    > knew anything about what those capacitors do? Why does the board
    > still work?


    It is common on digital electronics to have a large number of decoupling
    capacitors. Sometimes one might have one by each chip as close to the chip as
    possible. But in practice it often does not matter too much if you reduce the
    number a bit. Its one of those things that you can't really have too much of
    (witin reason), but you can have too little. On low cost electronics, it is not
    unknown to see no decoupling capacitors at all!!

    So it does not surprise me your board still works. I suspect it might be a bit
    less reliable though. But you have the advantage there was probably a genorous
    amount to start with in a Sun. But for 3 to be misplaced, I would certainly
    repair or return it.

    How have they fallen off? I suspect it is physical abuse that has caused it. I
    don't think that is Sun's fault.

    > This is the second CPU I've gotten with capacitors broken off.
    > I don't whether that's Sun's fault or the USPS's...


    One of my X1195A's had a fault. It cooked itself, but it was obvious on
    inspection that one of the heatsinks was on wrong. Whether that was manufactured
    like it, or someone pulled it apart and put it back together wrong I don't know,
    but it was clearly different from the other 3 in the machine, and clearly never
    going to cool properly.


    > Bill



    --
    Dave K MCSE.

    MCSE = Minefield Consultant and Solitaire Expert.

    Please note my email address changes periodically to avoid spam.
    It is always of the form: month-year@domain. Hitting reply will work
    for a couple of months only. Later set it manually.

  3. Re: Broken (?) CPU module

    On 2006-04-10 20:03:29 -0400, "Dave (from the UK)"
    said:

    > So it does not surprise me your board still works. I suspect it might
    > be a bit less reliable though. But you have the advantage there was
    > probably a genorous amount to start with in a Sun. But for 3 to be
    > misplaced, I would certainly repair or return it.
    >
    > How have they fallen off? I suspect it is physical abuse that has
    > caused it. I don't think that is Sun's fault.


    As there was no sign of the third missing
    capacitor in the packaging (and it was packed
    quite well) I think it was probably broken at the
    time the person who sold it to me packed it and not
    during transit. The capacitors in question are the
    three immediately next to the hole for the plastic
    cover's mount. I imagine someone at one time replaced
    the cover with a little too much force and the leg
    slipped, knocking them off.

    They seem to be connected immediately to the
    edge connectors so I suspected they were for decoupling,
    but I don't know enough about electronics to
    be sure. As it was a $20 eBay purchase I'm not sure
    returning it would be worth it, especially since
    it has to go back to Canada. It's been running
    seemingly fine for the last three hours or so now.
    I'm compiling Mozilla and it's OK -- the last
    faulty processor I had would always cause the
    system to panic when the load average got above 1.5 or so.



  4. Re: Broken (?) CPU module



    Bill Green wrote:
    > On 2006-04-10 20:03:29 -0400, "Dave (from the UK)"
    > said:
    >
    >> So it does not surprise me your board still works. I suspect it might
    >> be a bit less reliable though. But you have the advantage there was
    >> probably a genorous amount to start with in a Sun. But for 3 to be
    >> misplaced, I would certainly repair or return it.
    >>
    >> How have they fallen off? I suspect it is physical abuse that has
    >> caused it. I don't think that is Sun's fault.

    >
    >
    > As there was no sign of the third missing
    > capacitor in the packaging (and it was packed
    > quite well) I think it was probably broken at the
    > time the person who sold it to me packed it and not
    > during transit. The capacitors in question are the
    > three immediately next to the hole for the plastic
    > cover's mount. I imagine someone at one time replaced
    > the cover with a little too much force and the leg
    > slipped, knocking them off.
    >
    > They seem to be connected immediately to the
    > edge connectors so I suspected they were for decoupling,
    > but I don't know enough about electronics to
    > be sure. As it was a $20 eBay purchase I'm not sure
    > returning it would be worth it, especially since
    > it has to go back to Canada. It's been running
    > seemingly fine for the last three hours or so now.
    > I'm compiling Mozilla and it's OK -- the last
    > faulty processor I had would always cause the
    > system to panic when the load average got above 1.5 or so.


    Given their location and type, they were almost certainly decoupling
    capacitors, so there will be some degradation of the three signals
    involved - but very possibly not sufficient to cause the system to lock
    up or panic. The fact the system has run for several hours is promising.

    Given the minimal investment and the hassle involved in returning and
    subsequently replacing the processor, my inclination would be to
    exercise the processor until it either fails or you feel you can trust it.

    Since I have experience with surface mount rework, I would re-install
    the two loose capacitors and pull one from my stock of dead boards to
    replace the missing capacitor - no more than half an hour's work. Got a
    friend who could do the same for you?

    Sunny

  5. Re: Broken (?) CPU module

    Bill Green wrote:
    > I got a 450MHz CPU (501-5339) for my U60 in the mail today.
    > Installed it, powered the machine up, everything seemed fine.
    > When I went to set the machine back upright I heard a rattle,
    > like a screw had fallen into the case. I took out the CPU
    > module and two surface-mount capacitors fell out of the module!
    > There are in total three capacitors missing from the
    > left-hand side of the top side of the board, right above the
    > connectors.
    >
    > Out of curiosity, and figuring it would've toasted the board
    > already if it were going to, I plugged it back in and booted
    > the machine up -- no complaints. I ran SunVTS's cpu tests for
    > about an hour and the module passed them.
    >
    > I know I should probably try and return the module and (sigh)
    > start looking for another one, but I was interested if anybody
    > knew anything about what those capacitors do? Why does the board
    > still work?
    >
    > This is the second CPU I've gotten with capacitors broken off.
    > I don't whether that's Sun's fault or the USPS's...
    >
    > Bill



    Why don't you just solder the capacitors back on? I'd use new ones
    personally, surface mount lytics tend to dry out.

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