[j-nsp] T4000 power architecture

[Sam Silvester]

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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