Pavilion 7800 no boot

Archived from groups: comp.sys.hp.hardware (More info?)

Hi All,
I have a HP Pavilion 7800 that won't boot up. The green light on the back
of the power supply is on. None of the fans spin, nor any of the drives.
When I push the start button on the front panel the only thing that happens
is the light on the CD-ROM drive blinks. I am hard of hearing so if any
beeps were present I would not hear them.
I would like to check the power supply but forgot what two pins on the
motherboard connector need to be jumped when the connector is unplugged. I
do remember that they were next to each other, if anyone can tell me I would
be most thankful.
Thanks
John
2 answers Last reply
More about pavilion 7800 boot
  1. Archived from groups: comp.sys.hp.hardware (More info?)

    John,

    I am not aware of any motherboard which requires jumpers or connectors to be set
    differently when the power supply is unplugged. This would be a little odd, but
    perhaps HP did choose an oddball motherboard.

    As a rule, the fans in a system spin only if the motherboard begins running,
    because the fans either draw their power directly from the motherboard or they
    are triggered by a circuit on the motherboard.

    My best guess is that something is not right with the motherboard, CPU or
    memory.

    Unplug the power cord whenever you are working on the innards of a computer.

    If the system is more than two or three years old, replace the C2032 3v
    motherboard battery, and try again. Failed or failing batteries can create all
    kinds of wierd symptoms. Also, remove and re-install the memory DIMMs. if one
    of them came loose, this could cause problems.

    To troubleshoot further, open up the case, and remove all boards (except a video
    card, if present), disconnect all external cables (except for keyboard, mouse
    and monitor), disconnect all power from floppy diskette, hard drive, and CD-ROM
    drive. Of course, remember where all these things connect up. Doing so gets
    down to a bare bones motherboard-CPU-memory-video setup. If the motherboard
    starts up and displays something on the monitor screen, you know the motherboard
    and power supply are good. If not, then you need more sophisticated diagnostic
    tools and/or extra parts to determine which component failed. If the board
    boots up, reconnect the other devices one at a time. If the system fails to
    boot after you connect up a device, disconnect it. It is likely the cause of
    failure... Ben Myers

    On Tue, 03 Aug 2004 10:54:51 GMT, "John Baiamonte" <donotrespond@all.com> wrote:

    >Hi All,
    > I have a HP Pavilion 7800 that won't boot up. The green light on the back
    >of the power supply is on. None of the fans spin, nor any of the drives.
    >When I push the start button on the front panel the only thing that happens
    >is the light on the CD-ROM drive blinks. I am hard of hearing so if any
    >beeps were present I would not hear them.
    > I would like to check the power supply but forgot what two pins on the
    >motherboard connector need to be jumped when the connector is unplugged. I
    >do remember that they were next to each other, if anyone can tell me I would
    >be most thankful.
    > Thanks
    > John
    >
    >
  2. Archived from groups: comp.sys.hp.hardware (More info?)

    Hey Ben,
    Thanks a lot for all the info I will follow your advise. The jumper I
    was referring to was the 20 pin connector coming from the power supply.
    Last year I had another computer fail and I disconnected the 20 pin
    connector from the mother board and used a paper clip to connect two of the
    pins on the connector and checked the voltages. All the pins were dead,
    bought a new power supply and everything worked fine. I just can't
    remember what two pin needed to be jumper. If you don't jump the two pins
    even a good power supply will test dead.


    <ben_myers_spam_me_not @ charter.net (Ben Myers)> wrote in message
    news:410f9564.4171820@news.charter.net...
    > John,
    >
    > I am not aware of any motherboard which requires jumpers or connectors to
    be set
    > differently when the power supply is unplugged. This would be a little
    odd, but
    > perhaps HP did choose an oddball motherboard.
    >
    > As a rule, the fans in a system spin only if the motherboard begins
    running,
    > because the fans either draw their power directly from the motherboard or
    they
    > are triggered by a circuit on the motherboard.
    >
    > My best guess is that something is not right with the motherboard, CPU or
    > memory.
    >
    > Unplug the power cord whenever you are working on the innards of a
    computer.
    >
    > If the system is more than two or three years old, replace the C2032 3v
    > motherboard battery, and try again. Failed or failing batteries can
    create all
    > kinds of wierd symptoms. Also, remove and re-install the memory DIMMs.
    if one
    > of them came loose, this could cause problems.
    >
    > To troubleshoot further, open up the case, and remove all boards (except a
    video
    > card, if present), disconnect all external cables (except for keyboard,
    mouse
    > and monitor), disconnect all power from floppy diskette, hard drive, and
    CD-ROM
    > drive. Of course, remember where all these things connect up. Doing so
    gets
    > down to a bare bones motherboard-CPU-memory-video setup. If the
    motherboard
    > starts up and displays something on the monitor screen, you know the
    motherboard
    > and power supply are good. If not, then you need more sophisticated
    diagnostic
    > tools and/or extra parts to determine which component failed. If the
    board
    > boots up, reconnect the other devices one at a time. If the system fails
    to
    > boot after you connect up a device, disconnect it. It is likely the cause
    of
    > failure... Ben Myers
    >
    > On Tue, 03 Aug 2004 10:54:51 GMT, "John Baiamonte" <donotrespond@all.com>
    wrote:
    >
    > >Hi All,
    > > I have a HP Pavilion 7800 that won't boot up. The green light on the
    back
    > >of the power supply is on. None of the fans spin, nor any of the drives.
    > >When I push the start button on the front panel the only thing that
    happens
    > >is the light on the CD-ROM drive blinks. I am hard of hearing so if any
    > >beeps were present I would not hear them.
    > > I would like to check the power supply but forgot what two pins on the
    > >motherboard connector need to be jumped when the connector is unplugged.
    I
    > >do remember that they were next to each other, if anyone can tell me I
    would
    > >be most thankful.
    > > Thanks
    > > John
    > >
    > >
    >
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