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Display problems after replacing IBM lap top main board

Discussion in 'Electronic Repair' started by Rick, May 21, 2007.

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  1. Rick

    Rick Guest


    IBM ThinkPad A21m 2628-PRU in question.

    I had to replace the main board due to the known "lock up" problems on
    some IBM models. Did it by the book - used the IBM Hardware Reference
    Manual for disassembly procedures.

    Now the display is screwed up. The IBM logo on boot is skewed about 40
    degrees and off center. (Interesting look, but not right.) When W2K
    loads the right two inches of the display are black. And the display
    "scrolls" off the bottom of the screen and isn't visible. In this mode
    it looks something like it's displaying 768x1024 instead of 1024x768.
    The same thing happens in DOS booted diagnostices - the display runs off
    the bottom of the screen, but it does fill the entire screen to the
    right edge.

    In W2K if I change out of "stretch" mode (Fn + F8) the display shrinks
    to about 4" wide by 6" tall, placed on the bottom left of the screen.

    Display is normal in all modes on an external monitor. Diagnostics
    reports no problems with the VGA system. The back light on the lcd
    display is working fine.

    On this IBM, probably other IBM's as well, the display panel is
    connected to a "sub card" via a *heavy* flat cable. (It's reinforced,
    and so stiff it has to be screwed down to the sub card hold it in place.
    It's not any kind of thin film type of cable.) The sub card connects to
    the main board. The sub card acts as a pass through for the display
    connections to the main board, contains the status LED's, and the lid
    close switch.

    Reseating the sub card and the display panel flat cable hasn't helped.
    Lifting or pressing on the flat cable doesn't change anything - the
    display is rock solid - but just wrong.

    Does this sound like a simple LCD flat cable failure? I haven't ventured
    into the insides of the display yet so I don't know if there is a cable
    failure lurking in there. Removal of the LCD panel wasn't required -
    just the cable connection to the sub card - to replace the main board.
    One other point is the IBM reference manual has you putting the display
    into positions you wouldn't ever do in routine use - flat open at a 180
    degree angle - as part of the disassembly process *before* you can get
    access to disconnect the display cable from the sub card.

    Anyone seen this problem before on an IBM lap top? Any troubleshooting
    suggestions appreciated.

  2. Morse

    Morse Guest

    Rick wrote:

    I don't know about IBM laptops, but on HP Omnibook 6000/6100 laptops there's
    an eeprom on the mainboard which sometimes has to be flashed (*not* the
    system BIOS) when the display is replaced, as manufacturers often source
    their LCDs from different manufacturers and specs of replacement displays
    may change during product life. When I bought a replacement mainboard for
    mine I had to use the HP display update utility (HP don't give it out, I
    had to get it from a 3rd party website) to get it to work correctly with
    the display as it wasn't configured for it.

    This could be completely irrelevant to your situation but perhaps worth
    looking into.

  3. Rick

    Rick Guest

    It might be relevant. Thanks.

    Before ordering any main board I called IBM directly to get part
    numbers, since their model/type matrix made no sense when looking this
    one up in the IBM Hardware Reference Manual. (HRM) The model number on
    this machine was only mentioned once in the HRM, as a completely
    different configuration than what I have (Less memory, different size
    drive, less video memory... Hell it told me I had an A22m, not an A21m.)

    IBM told me I had two main board options: One with 8MB video memory -
    same as my original - or one with 16MB video memory. IBM tech support
    swore up and down that both these main boards were compatible with an
    A21m model 2628-PRU.

    Since nothing is working right, last night I crossed checked the main
    board numbers IBM supplied against the HRM. The 8MB VGA main board cross
    referenced to several models of A21m with XGA displays. (Not mine, but
    at least they were also A21m's.) The main board with 16MB VGA cross
    referenced to only one model: an A21p with a UXGA display...

    Someone else suggested that although both the 8MB and 16MB VGA versions
    use the same video chipset (ATI Rage Mobility) the 16MB version of the
    main board is expecting to run at a different (higher) resolution than
    my lap top display and that's what is producing the weird results.

    Right now I have no idea if IBM has a similar fix as you had to use. I
    do know that they used at least two different XGA displays from
    different manufacturers in the model line so IBM might have a reason to
    have a similar utility. Sounds like I need to "dumb down" the VGA system
    from running at maximum resolution when booting to match the display

  4. Rick

    Rick Guest

    Nevermind. A second call to IBM confirmed that the first idiot I spoke
    to at IBM gave me incorrect information. The 16 MB VGA version of the
    main board isn't compatible with the display in this lap top.

  5. Morse

    Morse Guest

    Have they agreed to exchange the board for the correct one, Rick? I imagine
    this is a frighteningly expensive item? Laptop manufacturers love to fleece
    people for spare parts, which is one reason I'm reluctant to replace my
    Omnibook 6100. It's been patched up a few times with secondhand spares very
    cheaply, and bits are fairly readily available on eBay for them. If I bought
    a new one I just know it'd fail one day outside the warranty and I'd be left
    with a pile of junk!

  6. Rick

    Rick Guest

    BTW: You were right, in a side ways kind of manner. :cool: The 16 MB
    version of the board cross referenced to the only model A21 that came
    with a UXGA display. The main board with 8 MB video memory cross
    referenced to 4 models that only came with XGA displays. Still didn't
    cross reference to my model in the HRM, but that was enough to explain
    the display mysteries. The second call to IBM confirmed it - the 16MB
    VGA version expects to "see" a UXGA display and can't be dumbed down
    with an EEPROM utility to run at a lower resolution.

    I went through an IBM parts distributor that sells "refurbished by IBM"
    parts and new parts. Translates: IBM tested board with warranty,
    possibly a pull. (I asked them what "refurb" meant before I ordered.)
    But not an EPay mystery part with the usual "NEW PART BUT I HAVE NO IDEA
    IF IT WORKS NO REFUNDS" disclaimer.

    The wrong main board as a refurb. cost $155.00 and the correct one is
    $151.00. Free shipping. No hassles at all about the return. But the
    "Ouch!" is the distributor has a 25% restocking fee policy. I'm going to
    ask them if they will knock the restocking fee in half, since I got the
    RMA for the wrong board and placed the order for the correct board in
    the same phone call. The restocking fee is a bit stiff, but I certainly
    wasn't expecting IBM to give me bad information about compatible part

    New, the main board would have cost $575.00 - just ridiculous.

    FWIW they are at:

    And sell a ton of stuff and parts - not just for IBM lap tops. Just make
    sure you know what you are ordering because of that restocking fee.

  7. Morse

    Morse Guest

    Rick wrote:

    It's a racket many online companies seem to indulge in. I returned a 19" TFT
    monitor to an online seller here in the UK which was completely dead and
    tested thoroughly before I returned it to make sure I hadn't screwed up.
    They claimed it worked perfectly when they received it back of course, and
    tried to keep 60UKP of my money!

    One rather insistant phone call later and they agreed to drop the restocking
    fee, no doubt because I pointed out this was the second duff monitor they'd
    sent me- the first was damaged!
    I'd try getting the fee waived, remind them they are getting another sale
    and they may relent. You can always fall back on getting it halved if they
    won't waive it altogether.

    Yep, HP charge 800UKP for a display assembly (complete lid) for the Omnibook
    6100, and they don't, or at least didn't, sell spare parts like inverters
    or backlight tubes so you have to fork out 800 UKP or buy a new laptop.
    Even the hinges, which are highly prone to failure, were non-replaceable.
    I had to chuckle at this:

    Part No. F1711-69103

    Description: HP - PENTIUM II 300MHZ 32KB L1 CACHE 512KB L2 CACHE 66MHZ FSB

    I think that'll be on their shelves long enough to become a valuable
    antique. In fact, at that price it looks like it already has!

    I'd love to know how one refurbishes a CPU anyway!


  8. Install a new $3 fan.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  9. Rick

    Rick Guest

    Morse, you seen this one?

    Got the replacement board, slapped it in and...

    Dead. Well, let's call it barely on life support: The battery charge
    indicator works and the battery seems to be charging. At least I know
    the thing is getting power. But other than that, hit the power button
    and all I get is a split second of the cooling fan doing a twitch and
    the hard drive status LED flashes a split second - whether the hard
    drive is in the bay or not. Nothing else. None of the other status LED's
    light, no screen display - nuttin'.

    So far I've reseated the cpu, reseated the mini PCI card, reseated and
    then pulled the RAM, pulled the hard drive and CD ROM, pulled the
    battery. No change.

    I can't see how I could have introduced a short considering the way
    ThinkPads assemble. There are only 3 direct board to board connections
    and only one plastic insulation shield that goes under the keyboard. All
    screws are accounted for.

    Having pulled all components that the HRM said to pull and there is
    still no change any other suggestions for troubleshooting this? Or does
    it seem like a dead main board right out of the bag? What this one is
    doing is only slightly different than the won't power up problem with
    the original main board that went bad. I'm a little suspicious of the
    replacement board because it came with a CMOS battery and the mini PCI
    cables already attached - not "stock" items to come with an IBM
    replacement main board.

  10. bz

    bz Guest

    YEP. Other possibility is that 1) battery is bad, can't supply any
    significant current AND 2) power adapter is bad, can't supply any
    significant current. Try swapping with another unit if you can find anyone
    that has one.
    Even with NEW stock, chances of getting a bad replacement are significant.

    [you ARE sure you reconnected all the cables, etc., correctly, right? :)]

    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
  11. Rick

    Rick Guest


    Actually I did - I have two ThinkPads that use the same battery and PS -
    no difference.

    After I sent this I did two other things I forgot about: Pulled the CMOS
    battery. And tried the "secret" IBM trick to reset a stuck ThinkPad -
    remove battery pack and AC power, hit the power on button 10 times.
    Didn't help.
    Really? On new stock parts? See below about this particular part though:
    This made me so paranoid I even checked to make sure I didn't insert the
    "can only be inserted one way" cpu wrong. But thanks for asking. :cool:

    For all the "chinese puzzle box" disassenbly/assembly procedures you
    have to go through on ThinkPads there are next to no cables or
    connections you can screw up. The only cable connects stand out -
    because they have to be addressed in the disassembly/assembly. And those
    are only a ribbon for the floppy (in this model), a ribbon to the LCD
    display, a single cable for speakers and mic., and a cable to the mini
    PCI card. All keyed, of course. That's it for cables. The only other
    connections are 3 board to board snap in connections. All I'm saying is
    that after you have done it once it's practically impossible to do it
    wrong. But I checked anyway. :cool:

    I think I got a dud board that someone returned for a refund when they
    swapped it with their own defective board. (Not like that's ever
    happened before...) I looked further at the packaging and it leads me to
    believe it was a restock and not a direct from IBM part as promised. I
    also checked the IBM part number on it and it's the same number as the
    board I'm trying to replace. Which means it has the same inherent defect
    that led my original board to fail. I already know IBM has a different
    FRU number for the redesigned board.

    Since I can't do much of anything else at this point, I'm going to drop
    my original board back in just to see if all the peripherals are still
    ok. That board will at least boot, it's just a question of how long it
    will run before it locks up hard. (Lotso IBM ThinkPads out there with
    this "feature.") So if it powers up with the old board I know they sent
    me a dud.

    Onto board number *three* when I call this place on Tuesday. In case you
    missed it: Board #1 was ordered based on IBM saying it was compatible
    with this model ThinkPad. It wasn't. Worked, but wasn't compatible with
    the display. Board #2 - current dud. Board #3....?

    I'm either persistent or insane.

  12. bz

    bz Guest

    third choice: every one else is crazy! :)

    Good luck and it looks like you won't be bored for the next few days. :)

    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
  13. Rick

    Rick Guest

    Pulled it out, swapped back to the original board - everything works as
    well as it can with the original main board. At least it confirmed the
    main board they sent was definitely a dud. What a tedious PITA this is
    getting to be...

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