[j-nsp] T4000 power architecture

[Sam Silvester]

Pins 'seem' ok from a visual inspection.

Our support vendor is involved, however because of reasons I'm getting the
feeling we're now playing whack-a-mole with randomly replacing components,
as opposed to actually using the results from previous tests such as moving
the FPC to guide us towards a most likely culprit.

The reason I'd like to know if the PEM has 'individual' outputs / feeds to
each FPC vs. a bus arrangement vai the midplane is that will hopefully
prevent needlessly changing out the PEM if it's more likely the midplane,
or vice-versa.

Requests so far for a more detailed power architecture have been met with
being sent that same (basic) document over and over; you'd think somebody,
somewhere would have some more detailed insight into the power architecture
of these beasts.

Sam



On Thu, Sep 11, 2014 at 8:34 AM, Tom Storey <tom at snnap.net> wrote:

> Can you see any physical damage to any of the pins on the midplane? I
> and my colleagues have come across a number of damaged sockets, bent
> pins etc.
>
> May not be easy to do, but perhaps power cycle all of the inputs to
> that PEM, and perhaps unseat and inspect for damage on the pins for it
> as well.
>
> If not, JTAC and see what they say. I'd like to hear the outcome
> though, as I work a lot with Juniper routers, this could be a useful
> bit of knowledge!
>
> On 10 September 2014 23:36, Sam Silvester <sam.silvester at gmail.com> wrote:
> > Hi Aqeel - thanks for the reply.
> >
> > Agree 100% - the problem is, we only seem to be getting power to FPC0
> from
> > one PEM... have a look below (and also note that FPC1 is fine, as are the
> > rest of the FPCs).
> >
> > The question is - are we looking at a PEM fault here, or a midplane
> fault?
> > As per previous discussion, the FPC itself seems fine, as moving it to
> > another slot resolves the issue. Putting another card into slot 0 yields
> > the same result as below.
> >
> > PEM 0 status:
> >   State                      Online
> >   Temperature                32 degrees C / 89 degrees F
> >   DC Input:                  OK
> >                       Voltage(V)  Current(A)  Power(W)  Load(%)
> >       INPUT 0           54.750       4.312      236        9
> >       INPUT 1           54.500       6.000      327       13
> >       INPUT 2           54.625      11.750      641       26
> >       INPUT 3           54.750       6.125      335       13
> >       INPUT 4           54.250      10.500      569       23
> >       INPUT 5           54.500       6.062      330       13
> >   DC Output           Voltage(V)  Current(A)  Power(W)  Load(%)
> >       FPC 0             55.062       8.625      474       31
> >       FPC 1             55.250       4.062      224       14
> >
> > <...snip...>
> >
> > PEM 1 status:
> >   State                      Online
> >   Temperature                30 degrees C / 86 degrees F
> >   DC Input:                  OK
> >                       Voltage(V)  Current(A)  Power(W)  Load(%)
> >       INPUT 0           54.500       3.250      177        7
> >       INPUT 1           54.625       3.375      184        7
> >       INPUT 2           54.500      12.437      677       28
> >       INPUT 3           54.500       5.125      279       11
> >       INPUT 4           54.625      12.062      658       27
> >       INPUT 5           54.375       2.750      149        6
> >   DC Output           Voltage(V)  Current(A)  Power(W)  Load(%)
> >       FPC 0              0.000       0.000        0        0
> >       FPC 1             55.125       4.500      248       16
> >
> > <...snip...>
> >
> >
> >
> > On Wed, Sep 10, 2014 at 8:48 PM, aqeel ahmed <aqeelpk at yahoo.com> wrote:
> >
> >> Hi
> >>
> >> Though aimed for redundancy If system has both power supplies installed
> >> then it will automatically load balance and in case one power supply
> goes
> >> down then whole system will be on single power supply left working.
> >>
> >> For further details you can refer to following juniper document.
> >>
> >>
> >>
> http://www.juniper.net/techpubs/en_US/release-independent/junos/information-products/topic-collections/hardware/t-series/t4000/hwguide/t4000-hwguide.pdf
> >>
> >> Regards
> >>
> >>
> >>
> >>   On Wednesday, September 10, 2014 5:16 AM, Sam Silvester <
> >> sam.silvester at gmail.com> wrote:
> >>
> >>
> >> Howdy,
> >>
> >> Can anybody shed any light on how the PEMs on a T4000 actually
> distribute
> >> power to each FPC slot?
> >>
> >> Have the case of a single FPC slot that is showing power being received
> >> from only one of the PEMs, whilst all the other FPC slots are load
> sharing
> >> as expected.
> >>
> >> Replacing the FPC shows the same issue, so we're pretty happy that it's
> >> "slot specific".
> >>
> >> What I'm curious about is if the midplane has individual 'traces' (for
> lack
> >> of a better term) for supplying power to each FPC from the two PEMs, or
> if
> >> there is a common bus shared between all the FPCs from each PEM. The
> reason
> >> I ask is if the PEM only has a single connection to the midplane,
> replacing
> >> it seems pointless and instead it looks like we're better off replacing
> the
> >> midplane. If the PEM has individual outputs to each slot, then replacing
> >> the PEM seems like a reasonable approach.
> >>
> >> I've been pointed at the following document (
> >>
> >>
> http://www.juniper.net/documentation/en_US/release-independent/junos/topics/concept/power-supply-t4000-description.html
> >> )
> >> which is very light-on in terms of detail. Does anybody know if there
> is a
> >> more detailed document available (or even internally?) that we can ask
> >> about?
> >>
> >> Thanks!
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> >>
> >>
> >>
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