PSU on a VAXstation 4000 VLC - DEC

This is a discussion on PSU on a VAXstation 4000 VLC - DEC ; I think I have a faulty PSU on one of my VLCs. After a while of operation the machine will fail and reboot and then it gets into a reboot-stop-reboot cycle that does not even get past the memory test. ...

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Thread: PSU on a VAXstation 4000 VLC

  1. PSU on a VAXstation 4000 VLC

    I think I have a faulty PSU on one of my VLCs. After a while of operation
    the machine will fail and reboot and then it gets into a reboot-stop-reboot
    cycle that does not even get past the memory test. When I came to it this
    evening the PSU was cycling on and off at about 1-second intervals, the PSU
    fans would just start to move and then stop again, and there is a high
    frequency "blip" that goes in time with the power cycling on and off.

    Is this a dead PSU or might it be repairable? I have no real electronics
    experience, but I do have a soldering iron and I am aware that PSUs are
    especially dangerous to mess with.

    Thanks

    Rob



  2. Re: PSU on a VAXstation 4000 VLC


    "Robert Jarratt" wrote in message
    newsyNWi.26150$uH.9846@newsfe4-gui.ntli.net...
    >I think I have a faulty PSU on one of my VLCs. After a while of operation
    >the machine will fail and reboot and then it gets into a reboot-stop-reboot
    >cycle that does not even get past the memory test. When I came to it this
    >evening the PSU was cycling on and off at about 1-second intervals, the PSU
    >fans would just start to move and then stop again, and there is a high
    >frequency "blip" that goes in time with the power cycling on and off.
    >
    > Is this a dead PSU or might it be repairable? I have no real electronics
    > experience, but I do have a soldering iron and I am aware that PSUs are
    > especially dangerous to mess with.
    >
    > Thanks
    >
    > Rob
    >


    Further info. If I leave the PSU powered off for a while (just tried for 30
    minutes or so) it powers up normally, but there is a high-pitched whine
    coming from the PSU. When it was constantly cycling on and off I found that
    switching it off and on again immediately did not stop the on/off behaviour.

    Regards

    Rob



  3. Re: PSU on a VAXstation 4000 VLC

    Robert Jarratt wrote:
    >
    > "Robert Jarratt" wrote in message
    > newsyNWi.26150$uH.9846@newsfe4-gui.ntli.net...
    > >I think I have a faulty PSU on one of my VLCs. After a while of operation
    > >the machine will fail and reboot and then it gets into a reboot-stop-reboot
    > >cycle that does not even get past the memory test. When I came to it this
    > >evening the PSU was cycling on and off at about 1-second intervals, the PSU
    > >fans would just start to move and then stop again, and there is a high
    > >frequency "blip" that goes in time with the power cycling on and off.
    > >
    > > Is this a dead PSU or might it be repairable? I have no real electronics
    > > experience, but I do have a soldering iron and I am aware that PSUs are
    > > especially dangerous to mess with.
    > >
    > > Thanks
    > >
    > > Rob
    > >

    >
    > Further info. If I leave the PSU powered off for a while (just tried for 30
    > minutes or so) it powers up normally, but there is a high-pitched whine
    > coming from the PSU. When it was constantly cycling on and off I found that
    > switching it off and on again immediately did not stop the on/off behaviour.


    Hhmmm... Sounds like it may be a fan issue. The fan may eventrually stop,
    causing the system to overheat and begin to misbehave.

    Just a thought...

    --
    David J Dachtera
    dba DJE Systems
    http://www.djesys.com/

    Unofficial OpenVMS Marketing Home Page
    http://www.djesys.com/vms/market/

    Unofficial Affordable OpenVMS Home Page:
    http://www.djesys.com/vms/soho/

    Unofficial OpenVMS-IA32 Home Page:
    http://www.djesys.com/vms/ia32/

    Unofficial OpenVMS Hobbyist Support Page:
    http://www.djesys.com/vms/support/

  4. Re: PSU on a VAXstation 4000 VLC


    "David J Dachtera" wrote in message
    news:472BE110.B8196392@spam.comcast.net...
    > Robert Jarratt wrote:
    >>
    >> "Robert Jarratt" wrote in message
    >> newsyNWi.26150$uH.9846@newsfe4-gui.ntli.net...
    >> >I think I have a faulty PSU on one of my VLCs. After a while of
    >> >operation
    >> >the machine will fail and reboot and then it gets into a
    >> >reboot-stop-reboot
    >> >cycle that does not even get past the memory test. When I came to it
    >> >this
    >> >evening the PSU was cycling on and off at about 1-second intervals, the
    >> >PSU
    >> >fans would just start to move and then stop again, and there is a high
    >> >frequency "blip" that goes in time with the power cycling on and off.
    >> >
    >> > Is this a dead PSU or might it be repairable? I have no real
    >> > electronics
    >> > experience, but I do have a soldering iron and I am aware that PSUs are
    >> > especially dangerous to mess with.
    >> >
    >> > Thanks
    >> >
    >> > Rob
    >> >

    >>
    >> Further info. If I leave the PSU powered off for a while (just tried for
    >> 30
    >> minutes or so) it powers up normally, but there is a high-pitched whine
    >> coming from the PSU. When it was constantly cycling on and off I found
    >> that
    >> switching it off and on again immediately did not stop the on/off
    >> behaviour.

    >
    > Hhmmm... Sounds like it may be a fan issue. The fan may eventrually stop,
    > causing the system to overheat and begin to misbehave.
    >
    > Just a thought...
    >
    > --
    > David J Dachtera
    > dba DJE Systems
    > http://www.djesys.com/
    >
    > Unofficial OpenVMS Marketing Home Page
    > http://www.djesys.com/vms/market/
    >
    > Unofficial Affordable OpenVMS Home Page:
    > http://www.djesys.com/vms/soho/
    >
    > Unofficial OpenVMS-IA32 Home Page:
    > http://www.djesys.com/vms/ia32/
    >
    > Unofficial OpenVMS Hobbyist Support Page:
    > http://www.djesys.com/vms/support/


    I am not sure this is the case because after several hours of cycling
    rapidly in and off I would not expect the PSU to be hot (it is not hot to
    the touch) so it would not be heat preventing a restart. After leaving it a
    while the PSU starts again and the fans do turn. The whine also sounds more
    electronic than mechanical. I suspect that heat is the cause, but not
    excessive heat, just a component that can no longer work at normal operating
    temperature.

    Regards

    Rob



  5. Re: PSU on a VAXstation 4000 VLC

    "Robert Jarratt" wrote in
    news:jIZWi.118405$yN2.57669@newsfe7-gui.ntli.net:

    >
    > "David J Dachtera" wrote in message
    > news:472BE110.B8196392@spam.comcast.net...
    >> Robert Jarratt wrote:
    >>>
    >>> "Robert Jarratt" wrote in message
    >>> newsyNWi.26150$uH.9846@newsfe4-gui.ntli.net...
    >>> >I think I have a faulty PSU on one of my VLCs. After a while of
    >>> >operation
    >>> >the machine will fail and reboot and then it gets into a
    >>> >reboot-stop-reboot
    >>> >cycle that does not even get past the memory test. When I came to
    >>> >it this
    >>> >evening the PSU was cycling on and off at about 1-second intervals,
    >>> >the PSU
    >>> >fans would just start to move and then stop again, and there is a
    >>> >high frequency "blip" that goes in time with the power cycling on
    >>> >and off.
    >>> >
    >>> > Is this a dead PSU or might it be repairable? I have no real
    >>> > electronics
    >>> > experience, but I do have a soldering iron and I am aware that
    >>> > PSUs are especially dangerous to mess with.
    >>> >
    >>> > Thanks
    >>> >
    >>> > Rob
    >>> >
    >>>
    >>> Further info. If I leave the PSU powered off for a while (just tried
    >>> for 30
    >>> minutes or so) it powers up normally, but there is a high-pitched
    >>> whine coming from the PSU. When it was constantly cycling on and off
    >>> I found that
    >>> switching it off and on again immediately did not stop the on/off
    >>> behaviour.

    >>
    >> Hhmmm... Sounds like it may be a fan issue. The fan may eventrually
    >> stop, causing the system to overheat and begin to misbehave.
    >>
    >> Just a thought...
    >>
    >> --
    >> David J Dachtera
    >> dba DJE Systems
    >> http://www.djesys.com/
    >>
    >> Unofficial OpenVMS Marketing Home Page
    >> http://www.djesys.com/vms/market/
    >>
    >> Unofficial Affordable OpenVMS Home Page:
    >> http://www.djesys.com/vms/soho/
    >>
    >> Unofficial OpenVMS-IA32 Home Page:
    >> http://www.djesys.com/vms/ia32/
    >>
    >> Unofficial OpenVMS Hobbyist Support Page:
    >> http://www.djesys.com/vms/support/

    >
    > I am not sure this is the case because after several hours of cycling
    > rapidly in and off I would not expect the PSU to be hot (it is not hot
    > to the touch) so it would not be heat preventing a restart. After
    > leaving it a while the PSU starts again and the fans do turn. The
    > whine also sounds more electronic than mechanical. I suspect that heat
    > is the cause, but not excessive heat, just a component that can no
    > longer work at normal operating temperature.
    >
    > Regards
    >
    > Rob
    >
    >


    Let me suggest it may be a capacitor. If you can get at the internals of
    the power supply while it's in the repeated restart state, you should
    spray electronics coolant on capacitors, one by one, until the restarting
    stops. (It is only useful to spray those which you could replace.) I
    used a product called 63 Below when I was in college. I found a number
    of failing capacitors with this method. (Though we didn't use eye
    protection in college, I would recommend wearing them now, since they're
    cheap protection.)
    Good Luck.

    Tad

  6. Re: PSU on a VAXstation 4000 VLC

    Tad Winters wrote:
    >
    > "Robert Jarratt" wrote in
    > news:jIZWi.118405$yN2.57669@newsfe7-gui.ntli.net:
    >
    > >
    > > "David J Dachtera" wrote in message
    > > news:472BE110.B8196392@spam.comcast.net...
    > >> Robert Jarratt wrote:
    > >>>
    > >>> "Robert Jarratt" wrote in message
    > >>> newsyNWi.26150$uH.9846@newsfe4-gui.ntli.net...
    > >>> >I think I have a faulty PSU on one of my VLCs. After a while of
    > >>> >operation
    > >>> >the machine will fail and reboot and then it gets into a
    > >>> >reboot-stop-reboot
    > >>> >cycle that does not even get past the memory test. When I came to
    > >>> >it this
    > >>> >evening the PSU was cycling on and off at about 1-second intervals,
    > >>> >the PSU
    > >>> >fans would just start to move and then stop again, and there is a
    > >>> >high frequency "blip" that goes in time with the power cycling on
    > >>> >and off.
    > >>> >
    > >>> > Is this a dead PSU or might it be repairable? I have no real
    > >>> > electronics
    > >>> > experience, but I do have a soldering iron and I am aware that
    > >>> > PSUs are especially dangerous to mess with.
    > >>> >
    > >>> > Thanks
    > >>> >
    > >>> > Rob
    > >>> >
    > >>>
    > >>> Further info. If I leave the PSU powered off for a while (just tried
    > >>> for 30
    > >>> minutes or so) it powers up normally, but there is a high-pitched
    > >>> whine coming from the PSU. When it was constantly cycling on and off
    > >>> I found that
    > >>> switching it off and on again immediately did not stop the on/off
    > >>> behaviour.
    > >>
    > >> Hhmmm... Sounds like it may be a fan issue. The fan may eventrually
    > >> stop, causing the system to overheat and begin to misbehave.
    > >>
    > >> Just a thought...
    > >>
    > >> --
    > >> David J Dachtera
    > >> dba DJE Systems
    > >> http://www.djesys.com/
    > >>
    > >> Unofficial OpenVMS Marketing Home Page
    > >> http://www.djesys.com/vms/market/
    > >>
    > >> Unofficial Affordable OpenVMS Home Page:
    > >> http://www.djesys.com/vms/soho/
    > >>
    > >> Unofficial OpenVMS-IA32 Home Page:
    > >> http://www.djesys.com/vms/ia32/
    > >>
    > >> Unofficial OpenVMS Hobbyist Support Page:
    > >> http://www.djesys.com/vms/support/

    > >
    > > I am not sure this is the case because after several hours of cycling
    > > rapidly in and off I would not expect the PSU to be hot (it is not hot
    > > to the touch) so it would not be heat preventing a restart. After
    > > leaving it a while the PSU starts again and the fans do turn. The
    > > whine also sounds more electronic than mechanical. I suspect that heat
    > > is the cause, but not excessive heat, just a component that can no
    > > longer work at normal operating temperature.
    > >
    > > Regards
    > >
    > > Rob
    > >
    > >

    >
    > Let me suggest it may be a capacitor. If you can get at the internals of
    > the power supply while it's in the repeated restart state, you should
    > spray electronics coolant on capacitors, one by one, until the restarting
    > stops. (It is only useful to spray those which you could replace.) I
    > used a product called 63 Below when I was in college. I found a number
    > of failing capacitors with this method. (Though we didn't use eye
    > protection in college, I would recommend wearing them now, since they're
    > cheap protection.)
    > Good Luck.


    A can of pressurized duster may work, also, if inverted (like they tell you NOT
    to do).

    Agree with the eye protection.

    --
    David J Dachtera
    dba DJE Systems
    http://www.djesys.com/

    Unofficial OpenVMS Marketing Home Page
    http://www.djesys.com/vms/market/

    Unofficial Affordable OpenVMS Home Page:
    http://www.djesys.com/vms/soho/

    Unofficial OpenVMS-IA32 Home Page:
    http://www.djesys.com/vms/ia32/

    Unofficial OpenVMS Hobbyist Support Page:
    http://www.djesys.com/vms/support/

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