DS10L power supply mystery - VMS

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Thread: DS10L power supply mystery

  1. DS10L power supply mystery

    Power failure.
    DS10L has no choice but to shutdown :-(

    I switch off the breaker for the machine.
    After power has returned, I power the breaker back on.

    the DSL10L powers back on, fans are working, gree light in fron is on.
    But no output on (serial) console. Nothing, nada. No RMC either.

    Using the "power" button, I can power off and on the DS10L to the same
    effect.

    In the back, the air coming out of the power supply is warm, but air
    coming out of the rest is cool and at a lesser rate.

    Repeat cycle, same thing.

    The trick is to physically pull the power cord from back of the DS10L,
    wait a second or 3 and put it back in. At that point, the unit powers
    back on, I can hear the 2 disks spinning up, air flow in the back is
    greater and getting warmer quickly, and the opower up sequence is
    displayed on the console, machine boots normally.

    Can anyone explain this ?

    What would be the difference between unplugging the unit and using a
    large breaker to feed power back to it ?

  2. Re: DS10L power supply mystery

    JF Mezei wrote:
    > Power failure.
    > DS10L has no choice but to shutdown :-(
    >
    > I switch off the breaker for the machine.
    > After power has returned, I power the breaker back on.
    >
    > the DSL10L powers back on, fans are working, gree light in fron is on.
    > But no output on (serial) console. Nothing, nada. No RMC either.
    >
    > Using the "power" button, I can power off and on the DS10L to the same
    > effect.
    >
    > In the back, the air coming out of the power supply is warm, but air
    > coming out of the rest is cool and at a lesser rate.
    >
    > Repeat cycle, same thing.
    >
    > The trick is to physically pull the power cord from back of the DS10L,
    > wait a second or 3 and put it back in. At that point, the unit powers
    > back on, I can hear the 2 disks spinning up, air flow in the back is
    > greater and getting warmer quickly, and the opower up sequence is
    > displayed on the console, machine boots normally.
    >
    > Can anyone explain this ?
    >
    > What would be the difference between unplugging the unit and using a
    > large breaker to feed power back to it ?


    To summarize the power sequence you reported:

    1. Power fails. You switch the circuit breaker off.
    2. Power is restored. You switch the circuit breaker on. The power
    supply has power, but the logic does not. Conclusion: the power supply
    has "crowbarred", probably because power was out of specification just
    before it failed.
    3. You push the power button. The power supply shuts down.
    4. You push the power button again. The power supply is still
    crowbarred.
    5. Repeat steps 3 and 4 with the same results.
    6. You disconnect and reconnect the power cord. The power supply
    recovers, the DS10L is functional.

    When a power supply crowbars, in order to recover it needs to have power
    applied, then removed, then applied again. Using its power switch is
    insufficient. You could have removed power using the circuit breaker
    with the same effect as pulling the power cord, but you did not try
    this.

    I have seen this happen with PC power supplies, so it is not something
    specific to the DS10L. I don't know if it is a safety feature designed
    into modern power supplies, or just an unintended consequence of the
    design.

    I don't remember where I first heard the term "crowbar" used to describe
    this effect of power supplies, but I suspect it was taken from the old
    method of stopping a flying platform: the pilot placed a crowbar between
    the counter-rotating fans below him. The platform landed very quickly.
    John Sauter (John_Sauter@systemeyescomputerstore.com)

  3. Re: DS10L power supply mystery

    In article , John Sauter writes:
    >JF Mezei wrote:
    >> Power failure.
    >> DS10L has no choice but to shutdown :-(
    >>
    >> I switch off the breaker for the machine.
    >> After power has returned, I power the breaker back on.
    >>
    >> the DSL10L powers back on, fans are working, gree light in fron is on.
    >> But no output on (serial) console. Nothing, nada. No RMC either.
    >>
    >> Using the "power" button, I can power off and on the DS10L to the same
    >> effect.
    >>
    >> In the back, the air coming out of the power supply is warm, but air
    >> coming out of the rest is cool and at a lesser rate.
    >>
    >> Repeat cycle, same thing.
    >>
    >> The trick is to physically pull the power cord from back of the DS10L,
    >> wait a second or 3 and put it back in. At that point, the unit powers
    >> back on, I can hear the 2 disks spinning up, air flow in the back is
    >> greater and getting warmer quickly, and the opower up sequence is
    >> displayed on the console, machine boots normally.
    >>
    >> Can anyone explain this ?
    >>
    >> What would be the difference between unplugging the unit and using a
    >> large breaker to feed power back to it ?

    >
    >To summarize the power sequence you reported:
    >
    >1. Power fails. You switch the circuit breaker off.
    >2. Power is restored. You switch the circuit breaker on. The power
    >supply has power, but the logic does not. Conclusion: the power supply
    >has "crowbarred", probably because power was out of specification just
    >before it failed.
    >3. You push the power button. The power supply shuts down.
    >4. You push the power button again. The power supply is still
    >crowbarred.
    >5. Repeat steps 3 and 4 with the same results.
    >6. You disconnect and reconnect the power cord. The power supply
    >recovers, the DS10L is functional.
    >
    >When a power supply crowbars, in order to recover it needs to have power
    >applied, then removed, then applied again. Using its power switch is
    >insufficient. You could have removed power using the circuit breaker
    >with the same effect as pulling the power cord, but you did not try
    >this.
    >
    >I have seen this happen with PC power supplies, so it is not something
    >specific to the DS10L. I don't know if it is a safety feature designed
    >into modern power supplies, or just an unintended consequence of the
    >design.
    >
    >I don't remember where I first heard the term "crowbar" used to describe
    >this effect of power supplies, but I suspect it was taken from the old
    >method of stopping a flying platform: the pilot placed a crowbar between
    >the counter-rotating fans below him. The platform landed very quickly.


    The design of power supplies use a "crowbar circuit" to limit over-voltage
    conditions. Zener diodes and SCRs were common in older designs. How this
    is implemented in more modern switching supplies may be the same or some-
    thing completely different.

    --
    VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)COM

    .... pejorative statements of opinion are entitled to constitutional protection
    no matter how extreme, vituperous, or vigorously expressed they may be. (NJSC)

    Copr. 2008 Brian Schenkenberger. Publication of _this_ usenet article outside
    of usenet _must_ include its contents in its entirety including this copyright
    notice, disclaimer and quotations.

  4. Re: DS10L power supply mystery

    John Sauter writes:

    >I don't remember where I first heard the term "crowbar" used to describe
    >this effect of power supplies, but I suspect it was taken from the old
    >method of stopping a flying platform: the pilot placed a crowbar between
    >the counter-rotating fans below him. The platform landed very quickly.


    "Crowbar" wrt to a power supply is a circuit that deliberately
    short-circuits the supply's output in order to protect delicate
    electronics from an overvoltage condition or other fault. Ideally
    the crowbar trips a circuit breaker/blows a fuse and can be reset.
    The term "crowbar" comes from the idea of short-circuiting the power
    supply using a crowbar, which isn't far from what really happens.

    Nowadays power supplies usually have less crude protection logic, but
    often they require manual intervention such as removing power to reset
    them.

  5. Re: DS10L power supply mystery

    Michael Moroney wrote:

    > Nowadays power supplies usually have less crude protection logic, but
    > often they require manual intervention such as removing power to reset
    > them.


    But power was completely out for a few hours last night...

    And because I had switched up the breaker for that room, the alpha would
    not have seen transients when the power utility re-energized the
    neighbourhoud. I waited over half an hour before putting the breaker
    back to "ON".

    So you'd think a few hours without power would have reset the power
    supply :-)

    Would you guys suggest I perform additional tests ? (cutting poower
    abruptly and then applying it back some minutes later) ? My concern is
    that if the power supply is "weak", such tests would weaken it more.

  6. Re: DS10L power supply mystery

    JF Mezei wrote:
    > Michael Moroney wrote:
    >
    >> Nowadays power supplies usually have less crude protection logic, but
    >> often they require manual intervention such as removing power to reset
    >> them.

    >
    > But power was completely out for a few hours last night...
    >
    > And because I had switched up the breaker for that room, the alpha would
    > not have seen transients when the power utility re-energized the
    > neighbourhoud. I waited over half an hour before putting the breaker
    > back to "ON".
    >
    > So you'd think a few hours without power would have reset the power
    > supply :-)
    >
    > Would you guys suggest I perform additional tests ? (cutting poower
    > abruptly and then applying it back some minutes later) ? My concern is
    > that if the power supply is "weak", such tests would weaken it more.


    I don't know how to reliably crowbar a power supply, so I can't
    recommend a useful test. However, in my experience, the crowbar
    condition will not reset until good power is applied and then removed.
    No amount of waiting while the power is off will reset it.

    It is by no means certain that the power supply is ready to fail.
    I have seen power supplies run fine for years after crowbarring.
    John Sauter (John_Sauter@systemeyescomputerstore.com)

  7. Re: DS10L power supply mystery

    On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei wrote:
    > Power failure.
    > DS10L has no choice but to shutdown :-(
    >
    > I switch off the breaker for the machine.
    > After power has returned, I power the breaker back on.
    >
    > the DSL10L powers back on, fans are working, gree light in fron is on.
    > But no output on (serial) console. Nothing, nada. No RMC either.
    >
    > Using the "power" button, I can power off and on the DS10L to the same
    > effect.
    >
    > In the back, the air coming out of the power supply is warm, but air
    > coming out of the rest is cool and at a lesser rate.
    >
    > Repeat cycle, same thing.
    >
    > The trick is to physically pull the power cord from back of the DS10L,
    > wait a second or 3 and put it back in. At that point, the unit powers
    > back on, I can hear the 2 disks spinning up, air flow in the back is
    > greater and getting warmer quickly, and the opower up sequence is
    > displayed on the console, machine boots normally.
    >
    > Can anyone explain this ?
    >
    > What would be the difference between unplugging the unit and using a
    > large breaker to feed power back to it ?
    >


    Hi, jf

    probably cheaper to order an entire DS10L from our favorite vendor in
    Savannah/Tybee Island than it would be to find a power supply.

    WWWebb

  8. Re: DS10L power supply mystery

    William Webb wrote:
    > On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei wrote:
    >> Power failure.
    >> DS10L has no choice but to shutdown :-(
    >>
    >> I switch off the breaker for the machine.
    >> After power has returned, I power the breaker back on.
    >>
    >> the DSL10L powers back on, fans are working, gree light in fron is on.
    >> But no output on (serial) console. Nothing, nada. No RMC either.
    >>
    >> Using the "power" button, I can power off and on the DS10L to the same
    >> effect.
    >>
    >> In the back, the air coming out of the power supply is warm, but air
    >> coming out of the rest is cool and at a lesser rate.
    >>
    >> Repeat cycle, same thing.
    >>
    >> The trick is to physically pull the power cord from back of the DS10L,
    >> wait a second or 3 and put it back in. At that point, the unit powers
    >> back on, I can hear the 2 disks spinning up, air flow in the back is
    >> greater and getting warmer quickly, and the opower up sequence is
    >> displayed on the console, machine boots normally.
    >>
    >> Can anyone explain this ?
    >>
    >> What would be the difference between unplugging the unit and using a
    >> large breaker to feed power back to it ?
    >>

    >
    > Hi, jf
    >
    > probably cheaper to order an entire DS10L from our favorite vendor in
    > Savannah/Tybee Island than it would be to find a power supply.
    >
    > WWWebb


    That supply probably does not use a crowbard (SCR->ON). It probably
    stops drive to a switching transistor. There is likely an IC (or
    several) that has overvoltage, undervoltage, and overcurrent sensing and
    triggering any of these will stop it. It may also have a smaller standby
    type of switching supply internally, to keep the switching controller
    live, even if the main switcher (power factor controller) or one of the
    subordinate switchers is shut down.

    Repairing old/questionable switching power supplies is interesting and
    may produce spectacular results if something has been overlooked.

    One thing to check is using an oscilloscope, look for noise on each DC
    line from the switcher. They should have no more than about 50mV peak
    noise. A bad filter capacitor on any DC voltage can cause much noise to
    the point of causing shutdowns and even subtle things like unexplained
    errors or crashes. An ESR (equivalent series resistance) meter can be
    used to check the capacitors individually and a high ESR is a sure sign
    of a bad cap.

    I had a DG Nova 1200 that was given to me because it had blown most of
    the foil off all of the circuit boards and many chunks out of the couple
    hundred 14-pin DIP ICs during the previous owner's attempt to repair the
    switching power supply. In the dim time, switchers were new and
    cantankerous and few people understood them. It must have taken several
    seconds for the machine to die that horrible death and the poppencorken
    mit spitzensparken would have been enough to clear the room of any
    lurking veeblefesters.

    PJ

  9. Re: DS10L power supply mystery

    On Tue, Aug 19, 2008 at 11:49 PM, patrick jankowiak wrote:
    > William Webb wrote:
    >>
    >> On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei
    >> wrote:
    >>>
    >>> Power failure.
    >>> DS10L has no choice but to shutdown :-(
    >>>
    >>> I switch off the breaker for the machine.
    >>> After power has returned, I power the breaker back on.
    >>>
    >>> the DSL10L powers back on, fans are working, gree light in fron is on.
    >>> But no output on (serial) console. Nothing, nada. No RMC either.
    >>>
    >>> Using the "power" button, I can power off and on the DS10L to the same
    >>> effect.
    >>>
    >>> In the back, the air coming out of the power supply is warm, but air
    >>> coming out of the rest is cool and at a lesser rate.
    >>>
    >>> Repeat cycle, same thing.
    >>>
    >>> The trick is to physically pull the power cord from back of the DS10L,
    >>> wait a second or 3 and put it back in. At that point, the unit powers
    >>> back on, I can hear the 2 disks spinning up, air flow in the back is
    >>> greater and getting warmer quickly, and the opower up sequence is
    >>> displayed on the console, machine boots normally.
    >>>
    >>> Can anyone explain this ?
    >>>
    >>> What would be the difference between unplugging the unit and using a
    >>> large breaker to feed power back to it ?
    >>>

    >>
    >> Hi, jf
    >>
    >> probably cheaper to order an entire DS10L from our favorite vendor in
    >> Savannah/Tybee Island than it would be to find a power supply.
    >>
    >> WWWebb

    >
    > That supply probably does not use a crowbard (SCR->ON). It probably stops
    > drive to a switching transistor. There is likely an IC (or several) that has
    > overvoltage, undervoltage, and overcurrent sensing and triggering any of
    > these will stop it. It may also have a smaller standby type of switching
    > supply internally, to keep the switching controller live, even if the main
    > switcher (power factor controller) or one of the subordinate switchers is
    > shut down.
    >
    > Repairing old/questionable switching power supplies is interesting and may
    > produce spectacular results if something has been overlooked.
    >
    > One thing to check is using an oscilloscope, look for noise on each DC line
    > from the switcher. They should have no more than about 50mV peak noise. A
    > bad filter capacitor on any DC voltage can cause much noise to the point of
    > causing shutdowns and even subtle things like unexplained errors or crashes.
    > An ESR (equivalent series resistance) meter can be used to check the
    > capacitors individually and a high ESR is a sure sign of a bad cap.
    >
    > I had a DG Nova 1200 that was given to me because it had blown most of the
    > foil off all of the circuit boards and many chunks out of the couple hundred
    > 14-pin DIP ICs during the previous owner's attempt to repair the switching
    > power supply. In the dim time, switchers were new and cantankerous and few
    > people understood them. It must have taken several seconds for the machine
    > to die that horrible death and the poppencorken mit spitzensparken would
    > have been enough to clear the room of any lurking veeblefesters.
    >
    > PJ
    >


    Pat-

    The last time I saw field service use a scope was when they were
    troubleshooting an LP27.

    : - )

    WWWebb

  10. Re: DS10L power supply mystery

    On Aug 19, 9:13*pm, "William Webb" wrote:
    > probably cheaper to order an entire DS10L from our favorite vendor in
    > Savannah/Tybee Island than it would be to find a power supply.


    I have a DS10L with a bad power supply as well. I came across
    replacements somewhere online for around $80 (US). I bought the DS10L
    on eBay for around $150. So, the power supply is actually cheaper
    though I did choose to buy another DS10L anyway.

  11. Re: DS10L power supply mystery

    William Webb wrote:
    > On Tue, Aug 19, 2008 at 11:49 PM, patrick jankowiak wrote:
    >> William Webb wrote:
    >>> On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei
    >>> wrote:
    >>>> Power failure.
    >>>> DS10L has no choice but to shutdown :-(
    >>>>
    >>>> I switch off the breaker for the machine.
    >>>> After power has returned, I power the breaker back on.
    >>>>
    >>>> the DSL10L powers back on, fans are working, gree light in fron is on.
    >>>> But no output on (serial) console. Nothing, nada. No RMC either.
    >>>>
    >>>> Using the "power" button, I can power off and on the DS10L to the same
    >>>> effect.
    >>>>
    >>>> In the back, the air coming out of the power supply is warm, but air
    >>>> coming out of the rest is cool and at a lesser rate.
    >>>>
    >>>> Repeat cycle, same thing.
    >>>>
    >>>> The trick is to physically pull the power cord from back of the DS10L,
    >>>> wait a second or 3 and put it back in. At that point, the unit powers
    >>>> back on, I can hear the 2 disks spinning up, air flow in the back is
    >>>> greater and getting warmer quickly, and the opower up sequence is
    >>>> displayed on the console, machine boots normally.
    >>>>
    >>>> Can anyone explain this ?
    >>>>
    >>>> What would be the difference between unplugging the unit and using a
    >>>> large breaker to feed power back to it ?
    >>>>
    >>> Hi, jf
    >>>
    >>> probably cheaper to order an entire DS10L from our favorite vendor in
    >>> Savannah/Tybee Island than it would be to find a power supply.
    >>>
    >>> WWWebb

    >> That supply probably does not use a crowbard (SCR->ON). It probably stops
    >> drive to a switching transistor. There is likely an IC (or several) that has
    >> overvoltage, undervoltage, and overcurrent sensing and triggering any of
    >> these will stop it. It may also have a smaller standby type of switching
    >> supply internally, to keep the switching controller live, even if the main
    >> switcher (power factor controller) or one of the subordinate switchers is
    >> shut down.
    >>
    >> Repairing old/questionable switching power supplies is interesting and may
    >> produce spectacular results if something has been overlooked.
    >>
    >> One thing to check is using an oscilloscope, look for noise on each DC line
    >> from the switcher. They should have no more than about 50mV peak noise. A
    >> bad filter capacitor on any DC voltage can cause much noise to the point of
    >> causing shutdowns and even subtle things like unexplained errors or crashes.
    >> An ESR (equivalent series resistance) meter can be used to check the
    >> capacitors individually and a high ESR is a sure sign of a bad cap.
    >>
    >> I had a DG Nova 1200 that was given to me because it had blown most of the
    >> foil off all of the circuit boards and many chunks out of the couple hundred
    >> 14-pin DIP ICs during the previous owner's attempt to repair the switching
    >> power supply. In the dim time, switchers were new and cantankerous and few
    >> people understood them. It must have taken several seconds for the machine
    >> to die that horrible death and the poppencorken mit spitzensparken would
    >> have been enough to clear the room of any lurking veeblefesters.
    >>
    >> PJ
    >>

    >
    > Pat-
    >
    > The last time I saw field service use a scope was when they were
    > troubleshooting an LP27.
    >
    > : - )
    >
    > WWWebb


    My last time was ca. 1984/85 on a VAX 11/750. My CE at the time was
    probably among the last who knew what to do with an oscilloscope. From
    about that time on, Field Service just swapped boards until the system
    started working again.

  12. Re: DS10L power supply mystery

    On Aug 20, 6:48*am, "Richard B. Gilbert"
    wrote:
    > William Webb wrote:
    > > On Tue, Aug 19, 2008 at 11:49 PM, patrick jankowiak wrote:
    > >> William Webb wrote:
    > >>> On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei
    > >>> wrote:
    > >>>> Power failure.
    > >>>> DS10L has no choice but to shutdown :-(

    >
    > >>>> I switch off the breaker for the machine.
    > >>>> After power has returned, I power the breaker back on.

    >
    > >>>> the DSL10L powers back on, fans are working, gree light in fron is on.
    > >>>> But no output on (serial) console. Nothing, nada. No RMC either.

    >
    > >>>> Using the "power" button, I can power off and on the DS10L to the same
    > >>>> effect.

    >
    > >>>> In the back, the air coming out of the power supply is warm, but air
    > >>>> coming out of the rest is cool and at a lesser rate.

    >
    > >>>> Repeat cycle, same thing.

    >
    > >>>> The trick is to physically pull the power cord from back of the DS10L,
    > >>>> wait a second or 3 and put it back in. At that point, the unit powers
    > >>>> back on, I can hear the 2 disks spinning up, air flow in the back is
    > >>>> greater and getting warmer quickly, and the opower up sequence is
    > >>>> displayed on the console, machine boots normally.

    >
    > >>>> Can anyone explain this ?

    >
    > >>>> What would be the difference between unplugging the unit and using a
    > >>>> large breaker to feed power back to it ?

    >
    > >>> Hi, jf

    >
    > >>> probably cheaper to order an entire DS10L from our favorite vendor in
    > >>> Savannah/Tybee Island than it would be to find a power supply.

    >
    > >>> WWWebb
    > >> That supply probably does not use a crowbard (SCR->ON). It probably stops
    > >> drive to a switching transistor. There is likely an IC (or several) that has
    > >> overvoltage, undervoltage, and overcurrent sensing and triggering any of
    > >> these will stop it. It may also have a smaller standby type of switching
    > >> supply internally, to keep the switching controller live, even if the main
    > >> switcher (power factor controller) or one of the subordinate switchersis
    > >> shut down.

    >
    > >> Repairing old/questionable switching power supplies is interesting andmay
    > >> produce spectacular results if something has been overlooked.

    >
    > >> One thing to check is using an oscilloscope, look for noise on each DCline
    > >> from the switcher. They should have no more than about 50mV peak noise.. A
    > >> bad filter capacitor on any DC voltage can cause much noise to the point of
    > >> causing shutdowns and even subtle things like unexplained errors or crashes.
    > >> An ESR (equivalent series resistance) meter can be used to check the
    > >> capacitors individually and a high ESR is a sure sign of a bad cap.

    >
    > >> I had a DG Nova 1200 that was given to me because it had blown most ofthe
    > >> foil off all of the circuit boards and many chunks out of the couple hundred
    > >> 14-pin DIP ICs during the previous owner's attempt to repair the switching
    > >> power supply. In the dim time, switchers were new and cantankerous andfew
    > >> people understood them. It must have taken several seconds for the machine
    > >> to die that horrible death and the poppencorken mit spitzensparken would
    > >> have been enough to clear the room of any lurking veeblefesters.

    >
    > >> PJ

    >
    > > Pat-

    >
    > > The last time I saw field service use a scope was when they were
    > > troubleshooting an LP27.

    >
    > > : - )

    >
    > > WWWebb

    >
    > My last time was ca. 1984/85 on a VAX 11/750. *My CE at the time was
    > probably among the last who knew what to do with an oscilloscope. *From
    > about that time on, Field Service just swapped boards until the system
    > started working again.- Hide quoted text -
    >
    > - Show quoted text -


    We had a scope (Tektronics, not HP:0) here last millenium. I once
    turned it on and started playing with it - I'd used scopes for years
    in a former life - and some asked me "what's that?" I guess they'd
    never seen bad sci-fi movies growing up or heard the TV lines - do not
    attempt to adjust your vertical or horizontal, we are in control; or
    words to that affect. Remember?


  13. Re: DS10L power supply mystery

    As these Power supplies are not customer-repairable why not buy a spare for
    $49 ?

    We have hundreds in stock

    David

    --
    David B Turner

    =============================================

    Island Computers US Corp
    PO Box 86
    Tybee GA 31328

    Toll Free: 1-877 636 4332 x201, Mobile x251
    Email: dturner@islandco.com
    International & Local: (001)- 404-806-7749
    Fax: 912 786 8505
    Web: www.islandco.com

    =============================================
    "JF Mezei" wrote in message
    news:48ab1933$0$1829$c3e8da3@news.astraweb.com...
    > Michael Moroney wrote:
    >
    >> Nowadays power supplies usually have less crude protection logic, but
    >> often they require manual intervention such as removing power to reset
    >> them.

    >
    > But power was completely out for a few hours last night...
    >
    > And because I had switched up the breaker for that room, the alpha would
    > not have seen transients when the power utility re-energized the
    > neighbourhoud. I waited over half an hour before putting the breaker
    > back to "ON".
    >
    > So you'd think a few hours without power would have reset the power
    > supply :-)
    >
    > Would you guys suggest I perform additional tests ? (cutting poower
    > abruptly and then applying it back some minutes later) ? My concern is
    > that if the power supply is "weak", such tests would weaken it more.




  14. Re: DS10L power supply mystery

    On Aug 20, 3:20 pm, DaveG wrote:
    > On Aug 20, 6:48 am, "Richard B. Gilbert"
    > wrote:
    >
    >
    >
    > > William Webb wrote:
    > > > On Tue, Aug 19, 2008 at 11:49 PM, patrick jankowiak wrote:
    > > >> William Webb wrote:
    > > >>> On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei
    > > >>> wrote:
    > > >>>> Power failure.
    > > >>>> DS10L has no choice but to shutdown :-(

    >
    > > >>>> I switch off the breaker for the machine.
    > > >>>> After power has returned, I power the breaker back on.

    >
    > > >>>> the DSL10L powers back on, fans are working, gree light in fron is on.
    > > >>>> But no output on (serial) console. Nothing, nada. No RMC either.

    >
    > > >>>> Using the "power" button, I can power off and on the DS10L to the same
    > > >>>> effect.

    >
    > > >>>> In the back, the air coming out of the power supply is warm, but air
    > > >>>> coming out of the rest is cool and at a lesser rate.

    >
    > > >>>> Repeat cycle, same thing.

    >
    > > >>>> The trick is to physically pull the power cord from back of the DS10L,
    > > >>>> wait a second or 3 and put it back in. At that point, the unit powers
    > > >>>> back on, I can hear the 2 disks spinning up, air flow in the back is
    > > >>>> greater and getting warmer quickly, and the opower up sequence is
    > > >>>> displayed on the console, machine boots normally.

    >
    > > >>>> Can anyone explain this ?

    >
    > > >>>> What would be the difference between unplugging the unit and using a
    > > >>>> large breaker to feed power back to it ?

    >
    > > >>> Hi, jf

    >
    > > >>> probably cheaper to order an entire DS10L from our favorite vendor in
    > > >>> Savannah/Tybee Island than it would be to find a power supply.

    >
    > > >>> WWWebb
    > > >> That supply probably does not use a crowbard (SCR->ON). It probably stops
    > > >> drive to a switching transistor. There is likely an IC (or several) that has
    > > >> overvoltage, undervoltage, and overcurrent sensing and triggering any of
    > > >> these will stop it. It may also have a smaller standby type of switching
    > > >> supply internally, to keep the switching controller live, even if the main
    > > >> switcher (power factor controller) or one of the subordinate switchers is
    > > >> shut down.

    >
    > > >> Repairing old/questionable switching power supplies is interesting and may
    > > >> produce spectacular results if something has been overlooked.

    >
    > > >> One thing to check is using an oscilloscope, look for noise on each DC line
    > > >> from the switcher. They should have no more than about 50mV peak noise. A
    > > >> bad filter capacitor on any DC voltage can cause much noise to the point of
    > > >> causing shutdowns and even subtle things like unexplained errors or crashes.
    > > >> An ESR (equivalent series resistance) meter can be used to check the
    > > >> capacitors individually and a high ESR is a sure sign of a bad cap.

    >
    > > >> I had a DG Nova 1200 that was given to me because it had blown most of the
    > > >> foil off all of the circuit boards and many chunks out of the couple hundred
    > > >> 14-pin DIP ICs during the previous owner's attempt to repair the switching
    > > >> power supply. In the dim time, switchers were new and cantankerous and few
    > > >> people understood them. It must have taken several seconds for the machine
    > > >> to die that horrible death and the poppencorken mit spitzensparken would
    > > >> have been enough to clear the room of any lurking veeblefesters.

    >
    > > >> PJ

    >
    > > > Pat-

    >
    > > > The last time I saw field service use a scope was when they were
    > > > troubleshooting an LP27.

    >
    > > > : - )

    >
    > > > WWWebb

    >
    > > My last time was ca. 1984/85 on a VAX 11/750. My CE at the time was
    > > probably among the last who knew what to do with an oscilloscope. From
    > > about that time on, Field Service just swapped boards until the system
    > > started working again.- Hide quoted text -

    >
    > > - Show quoted text -

    >
    > We had a scope (Tektronics, not HP:0) here last millenium. I once
    > turned it on and started playing with it - I'd used scopes for years
    > in a former life - and some asked me "what's that?" I guess they'd
    > never seen bad sci-fi movies growing up or heard the TV lines - do not
    > attempt to adjust your vertical or horizontal, we are in control; or
    > words to that affect. Remember?


    No, don't remember that at all. Definitely not.

    Others apparently do though: http://www.youtube.com/watch?v=vmY8gTG8f5E

    Last DEC engineer I remember using a scope would probably be doing
    RM03 head alignment (attached to an 11/70). Or maybe something deep
    inside a TU16?

    ps
    stay behind after class for mis-spelling Tektronix.
    pps
    for any flash-impaired and Youtube-incompatible readers here, the
    series was (in case it's not obvious) The Outer Limits.

  15. Re: DS10L power supply mystery

    On Aug 20, 9:50*am, johnwalla...@yahoo.co.uk wrote:
    > On Aug 20, 3:20 pm, DaveG wrote:
    >
    >
    >
    > > On Aug 20, 6:48 am, "Richard B. Gilbert"
    > > wrote:

    >
    > > > William Webb wrote:
    > > > > On Tue, Aug 19, 2008 at 11:49 PM, patrick jankowiak wrote:
    > > > >> William Webb wrote:
    > > > >>> On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei
    > > > >>> wrote:
    > > > >>>> Power failure.
    > > > >>>> DS10L has no choice but to shutdown :-(

    >
    > > > >>>> I switch off the breaker for the machine.
    > > > >>>> After power has returned, I power the breaker back on.

    >
    > > > >>>> the DSL10L powers back on, fans are working, gree light in fron is on.
    > > > >>>> But no output on (serial) console. Nothing, nada. No RMC either.

    >
    > > > >>>> Using the "power" button, I can power off and on the DS10L to the same
    > > > >>>> effect.

    >
    > > > >>>> In the back, the air coming out of the power supply is warm, butair
    > > > >>>> coming out of the rest is cool and at a lesser rate.

    >
    > > > >>>> Repeat cycle, same thing.

    >
    > > > >>>> The trick is to physically pull the power cord from back of the DS10L,
    > > > >>>> wait a second or 3 and put it back in. At that point, the unit powers
    > > > >>>> back on, I can hear the 2 disks spinning up, air flow in the back is
    > > > >>>> greater and getting warmer quickly, and the opower up sequence is
    > > > >>>> displayed on the console, machine boots normally.

    >
    > > > >>>> Can anyone explain this ?

    >
    > > > >>>> What would be the difference between unplugging the unit and using a
    > > > >>>> large breaker to feed power back to it ?

    >
    > > > >>> Hi, jf

    >
    > > > >>> probably cheaper to order an entire DS10L from our favorite vendor in
    > > > >>> Savannah/Tybee Island than it would be to find a power supply.

    >
    > > > >>> WWWebb
    > > > >> That supply probably does not use a crowbard (SCR->ON). It probably stops
    > > > >> drive to a switching transistor. There is likely an IC (or several) that has
    > > > >> overvoltage, undervoltage, and overcurrent sensing and triggering any of
    > > > >> these will stop it. It may also have a smaller standby type of switching
    > > > >> supply internally, to keep the switching controller live, even if the main
    > > > >> switcher (power factor controller) or one of the subordinate switchers is
    > > > >> shut down.

    >
    > > > >> Repairing old/questionable switching power supplies is interestingand may
    > > > >> produce spectacular results if something has been overlooked.

    >
    > > > >> One thing to check is using an oscilloscope, look for noise on each DC line
    > > > >> from the switcher. They should have no more than about 50mV peak noise. A
    > > > >> bad filter capacitor on any DC voltage can cause much noise to thepoint of
    > > > >> causing shutdowns and even subtle things like unexplained errors or crashes.
    > > > >> An ESR (equivalent series resistance) meter can be used to check the
    > > > >> capacitors individually and a high ESR is a sure sign of a bad cap..

    >
    > > > >> I had a DG Nova 1200 that was given to me because it had blown most of the
    > > > >> foil off all of the circuit boards and many chunks out of the couple hundred
    > > > >> 14-pin DIP ICs during the previous owner's attempt to repair the switching
    > > > >> power supply. In the dim time, switchers were new and cantankerousand few
    > > > >> people understood them. It must have taken several seconds for themachine
    > > > >> to die that horrible death and the poppencorken mit spitzensparkenwould
    > > > >> have been enough to clear the room of any lurking veeblefesters.

    >
    > > > >> PJ

    >
    > > > > Pat-

    >
    > > > > The last time I saw field service use a scope was when they were
    > > > > troubleshooting an LP27.

    >
    > > > > : - )

    >
    > > > > WWWebb

    >
    > > > My last time was ca. 1984/85 on a VAX 11/750. *My CE at the time was
    > > > probably among the last who knew what to do with an oscilloscope. *From
    > > > about that time on, Field Service just swapped boards until the system
    > > > started working again.- Hide quoted text -

    >
    > > > - Show quoted text -

    >
    > > We had a scope (Tektronics, not HP:0) here last millenium. *I once
    > > turned it on and started playing with it - I'd used scopes for years
    > > in a former life - and some asked me "what's that?" *I guess they'd
    > > never seen bad sci-fi movies growing up or heard the TV lines - do not
    > > attempt to adjust your vertical or horizontal, we are in control; or
    > > words to that affect. *Remember?

    >
    > No, don't remember that at all. Definitely not.
    >
    > Others apparently do though:http://www.youtube.com/watch?v=vmY8gTG8f5E
    >
    > Last DEC engineer I remember using a scope would probably be doing
    > RM03 head alignment (attached to an 11/70). Or maybe something deep
    > inside a TU16?
    >
    > ps
    > stay behind after class for mis-spelling Tektronix.
    > pps
    > for any flash-impaired and Youtube-incompatible readers here, the
    > series was (in case it's not obvious) The Outer Limits.


    I indeed mis-spelled Tektronix. My bad and I'll write that many times
    on a black board when I find one. ;-)

  16. Re: DS10L power supply mystery

    In article
    <6446e741-2f0a-49f5-9bbd-c860506a6714@z72g2000hsb.googlegroups.com>,
    johnwallace4@yahoo.co.uk wrote:

    > On Aug 20, 3:20 pm, DaveG wrote:
    > > On Aug 20, 6:48 am, "Richard B. Gilbert"
    > > wrote:
    > >
    > >
    > >
    > > > William Webb wrote:
    > > > > On Tue, Aug 19, 2008 at 11:49 PM, patrick jankowiak
    > > > > wrote:
    > > > >> William Webb wrote:
    > > > >>> On Tue, Aug 19, 2008 at 3:56 AM, JF Mezei
    > > > >>>
    > > > >>> wrote:
    > > > >>>> Power failure.
    > > > >>>> DS10L has no choice but to shutdown :-(

    > >
    > > > >>>> I switch off the breaker for the machine.
    > > > >>>> After power has returned, I power the breaker back on.

    > >
    > > > >>>> the DSL10L powers back on, fans are working, gree light in fron is
    > > > >>>> on.
    > > > >>>> But no output on (serial) console. Nothing, nada. No RMC either.

    > >
    > > > >>>> Using the "power" button, I can power off and on the DS10L to the
    > > > >>>> same
    > > > >>>> effect.

    > >
    > > > >>>> In the back, the air coming out of the power supply is warm, but air
    > > > >>>> coming out of the rest is cool and at a lesser rate.

    > >
    > > > >>>> Repeat cycle, same thing.

    > >
    > > > >>>> The trick is to physically pull the power cord from back of the
    > > > >>>> DS10L,
    > > > >>>> wait a second or 3 and put it back in. At that point, the unit
    > > > >>>> powers
    > > > >>>> back on, I can hear the 2 disks spinning up, air flow in the back is
    > > > >>>> greater and getting warmer quickly, and the opower up sequence is
    > > > >>>> displayed on the console, machine boots normally.

    > >
    > > > >>>> Can anyone explain this ?

    > >
    > > > >>>> What would be the difference between unplugging the unit and using a
    > > > >>>> large breaker to feed power back to it ?

    > >
    > > > >>> Hi, jf

    > >
    > > > >>> probably cheaper to order an entire DS10L from our favorite vendor in
    > > > >>> Savannah/Tybee Island than it would be to find a power supply.

    > >
    > > > >>> WWWebb
    > > > >> That supply probably does not use a crowbard (SCR->ON). It probably
    > > > >> stops
    > > > >> drive to a switching transistor. There is likely an IC (or several)
    > > > >> that has
    > > > >> overvoltage, undervoltage, and overcurrent sensing and triggering any
    > > > >> of
    > > > >> these will stop it. It may also have a smaller standby type of
    > > > >> switching
    > > > >> supply internally, to keep the switching controller live, even if the
    > > > >> main
    > > > >> switcher (power factor controller) or one of the subordinate switchers
    > > > >> is
    > > > >> shut down.

    > >
    > > > >> Repairing old/questionable switching power supplies is interesting and
    > > > >> may
    > > > >> produce spectacular results if something has been overlooked.

    > >
    > > > >> One thing to check is using an oscilloscope, look for noise on each DC
    > > > >> line
    > > > >> from the switcher. They should have no more than about 50mV peak
    > > > >> noise. A
    > > > >> bad filter capacitor on any DC voltage can cause much noise to the
    > > > >> point of
    > > > >> causing shutdowns and even subtle things like unexplained errors or
    > > > >> crashes.
    > > > >> An ESR (equivalent series resistance) meter can be used to check the
    > > > >> capacitors individually and a high ESR is a sure sign of a bad cap.

    > >
    > > > >> I had a DG Nova 1200 that was given to me because it had blown most of
    > > > >> the
    > > > >> foil off all of the circuit boards and many chunks out of the couple
    > > > >> hundred
    > > > >> 14-pin DIP ICs during the previous owner's attempt to repair the
    > > > >> switching
    > > > >> power supply. In the dim time, switchers were new and cantankerous and
    > > > >> few
    > > > >> people understood them. It must have taken several seconds for the
    > > > >> machine
    > > > >> to die that horrible death and the poppencorken mit spitzensparken
    > > > >> would
    > > > >> have been enough to clear the room of any lurking veeblefesters.

    > >
    > > > >> PJ

    > >
    > > > > Pat-

    > >
    > > > > The last time I saw field service use a scope was when they were
    > > > > troubleshooting an LP27.

    > >
    > > > > : - )

    > >
    > > > > WWWebb

    > >
    > > > My last time was ca. 1984/85 on a VAX 11/750. My CE at the time was
    > > > probably among the last who knew what to do with an oscilloscope. From
    > > > about that time on, Field Service just swapped boards until the system
    > > > started working again.- Hide quoted text -

    > >
    > > > - Show quoted text -

    > >
    > > We had a scope (Tektronics, not HP:0) here last millenium. I once
    > > turned it on and started playing with it - I'd used scopes for years
    > > in a former life - and some asked me "what's that?" I guess they'd
    > > never seen bad sci-fi movies growing up or heard the TV lines - do not
    > > attempt to adjust your vertical or horizontal, we are in control; or
    > > words to that affect. Remember?

    >
    > No, don't remember that at all. Definitely not.
    >
    > Others apparently do though: http://www.youtube.com/watch?v=vmY8gTG8f5E


    Do you remember "Do Not Adjust Your Set"? (A UK kids programme, also to
    be found on Youtube, and notable for Bonzo Dog Band and early
    appearances of Eric Idle, Terry Jones etc.).

    > Last DEC engineer I remember using a scope would probably be doing
    > RM03 head alignment (attached to an 11/70). Or maybe something deep
    > inside a TU16?


    Ditto, except with RM05s and an 11/750.

    --
    Paul Sture

  17. Re: DS10L power supply mystery

    On Aug 20, 5:23 pm, "P. Sture" wrote:
    > In article
    > <6446e741-2f0a-49f5-9bbd-c860506a6...@z72g2000hsb.googlegroups.com>,
    >
    >
    >
    > johnwalla...@yahoo.co.uk wrote:


    >
    > Do you remember "Do Not Adjust Your Set"? (A UK kids programme, also to
    > be found on Youtube, and notable for Bonzo Dog Band and early
    > appearances of Eric Idle, Terry Jones etc.).
    >
    > --
    > Paul Sture


    Vaguely recall DNAYS. It's apparently available on UK DVD (and,
    doubtless purely by coincidence, also lots of bits of DNAYS on
    Youtube). Under 4 at amazon.co.uk, or $15 at Amazon.Com - at last,
    something more expensive on Amazon US than here in the UK! There's
    also a US-released 2-DVD set including both DNAYS and At Last It's The
    1948 Show (UK readers beware, see reviews on Amazon.co.uk - half the
    material is missing in the UK 2-DVD equivalent). I guess DNAYS etc
    eventually led to things like Rutland Weekend TV (Idle, Innes, and
    friends), which I liked as much as some of the better-known bigger-
    budget stuff. Anything that brought the world The Rutles can't be all
    bad.

  18. Re: DS10L power supply mystery

    John Sauter wrote:

    > I don't remember where I first heard the term "crowbar" used to describe
    > this effect of power supplies, but I suspect it was taken from the old
    > method of stopping a flying platform: the pilot placed a crowbar between
    > the counter-rotating fans below him. The platform landed very quickly.
    > John Sauter (John_Sauter@systemeyescomputerstore.com)


    Back in the 60's when I was designing power supplies I was told the term
    came from the electric railway industry - apparently you could remove the
    power from an errant train by throwing a big enough literal crowbar across
    the rails. Recently I read an online discussion* about this. With the
    greater currents available these days it's more dangerous but apparently
    it is still done, rarely. I found it interesting that in the non-electric
    railroad industry the crowbar across the tracks will also declare that
    section of track as 'occupied' to the central office,** and prevent train
    access from adjacent sections.

    * http://cr4.globalspec.com/thread/246...de-application reply #16 by
    PWSlack who was replying to reply #8 in the thread.

    ** see reply #22 in the above thread.

    We are familiar with the term 'crowbar' here when our big mercury-vapour
    ignitrons short out our 4-megawatt 20-kV power supply to protect the
    expensive equipment it powers from damage as a result of sparking. Given
    the fact that high-current arc discharges have a self-focusing effect,
    with that much power available a spark can burn a hole in copper cooling
    water lines. In fact, the way you test an anti-sparking crowbar circuit
    is by slowly moving a calibrated grounded copper sheet slowly up to a
    calibrated sparking point until a spark happens. Without the crowbar
    circuit detecting the spark and dumping the energy harmlessly through
    the ignitrons, the spark would blow a big hole in the copper plate. When
    the crowbar circuit is operating properly there will be no hole in the
    copper plate.

    .. Fred Bach music at triumf dot c a .

  19. Re: DS10L power supply mystery

    JF Mezei wrote:
    > Michael Moroney wrote:
    >
    >
    >> Nowadays power supplies usually have less crude protection logic,
    >> but often they require manual intervention such as removing power
    >> to reset them.

    >
    >
    > But power was completely out for a few hours last night...
    >
    > And because I had switched up the breaker for that room, the alpha
    > would not have seen transients when the power utility re-energized
    > the neighbourhoud. I waited over half an hour before putting the
    > breaker back to "ON".
    >
    > So you'd think a few hours without power would have reset the power
    > supply :-)
    >
    > Would you guys suggest I perform additional tests ? (cutting poower
    > abruptly and then applying it back some minutes later) ? My concern
    > is that if the power supply is "weak", such tests would weaken it
    > more.


    The most likely cause is a flakey psu. Main protection is still usually
    an scr (cheap, simple and works well), even if this is augmented in / by the
    switcher control circuit. I have a pc that won't fire up unless it's
    left powered down for 10mins or so before reapplying power. Dec,
    however, were not pc vendors and were very fussy about system testing.
    Something like that would have been spotted early on and would never
    have made it through product acceptance.

    Try a different psu...

    Chris

  20. Re: DS10L power supply mystery

    In article
    <86efad5f-afdb-41d0-8276-1439d2c53b0c@a70g2000hsh.googlegroups.com>,
    johnwallace4@yahoo.co.uk wrote:

    > On Aug 20, 5:23 pm, "P. Sture" wrote:
    > >
    > > Do you remember "Do Not Adjust Your Set"? (A UK kids programme, also to
    > > be found on Youtube, and notable for Bonzo Dog Band and early
    > > appearances of Eric Idle, Terry Jones etc.).
    > >

    >
    > Vaguely recall DNAYS. It's apparently available on UK DVD (and,
    > doubtless purely by coincidence, also lots of bits of DNAYS on
    > Youtube). Under 4 at amazon.co.uk, or $15 at Amazon.Com - at last,
    > something more expensive on Amazon US than here in the UK! There's
    > also a US-released 2-DVD set including both DNAYS and At Last It's The
    > 1948 Show (UK readers beware, see reviews on Amazon.co.uk - half the
    > material is missing in the UK 2-DVD equivalent). I guess DNAYS etc
    > eventually led to things like Rutland Weekend TV (Idle, Innes, and
    > friends), which I liked as much as some of the better-known bigger-
    > budget stuff. Anything that brought the world The Rutles can't be all
    > bad.


    As I remember it, DNAYS started and ended with frames which looked as
    though your TV was on the blink, including upside down sequences, none
    of which I could find in the available Youtube clips.

    Thanks for the heads up about the DVD sets. I recall David Jason and
    Denise Coffey being main characters on the show. Very little of them
    seen on the Youtube clips.

    --
    Paul Sture