[j-nsp] T4000 power architecture

[Sam Silvester]

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!