[nsp] Funky PA-2T3 problems

[Temkin, David]

Certain revisions of the card are more susceptible to RX overload than
others.  I don't know how exactly to tell the difference, but I do know
it changed mid-stream at some point (because it was Cisco who wasn't
conforming to the standard...)

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Will
Sent: Wednesday, January 14, 2004 10:06 PM
To: cisco-nsp at puck.nether.net
Subject: [nsp] Funky PA-2T3 problems


I just finished turning up a DS3 between two 7204VXRs and had some weird
issues with the PA-2T3 cards I used.

Side 'A' has about 200' of 'customer coax' from the NIU to the PA-2T3.
Side 'B' has only about 20' of coax from the NIU. 'A' and 'B' are
connected by the LEC's SONET ring.

I had 4 PA-2T3 cards to work with, all purcahsed used (with a warranty
thankfully).

On side 'A', the rx clock LED would light 5-30 seconds after connecting
the rx cable, and would sometimes stay on for 30-90 seconds after
removing the cable. 'show controllers' would give rxLOS, txRAI active
and indicate received clockrate as a ridiculously low number like 1340
or so. Both ports on the card acted indentically. Swapped out with
another card and the line came right up with no problems.

On side 'B' with the line up I would get Line Code violations and rx CRC
errors, though the card would actually move data. I googled and found
that the signal might be too hot for the receiver. Not having any
attenuators handy, I tried longer patch cables (30' is the longest I
had) and the problems ddecreased but wouldn't go away. Swapped out with
another card and has now been clean for hours even with short cables.

I ruled out clocking/framing/dsu mode/scrambling as a factor in any of 
this and also tweaked with the cablelength parameter.

So do I really have 2 bad cards out of 4, one with fried receivers on
both ports and another with high sensitivity to rx overload on both
ports, while the other 2 cards work fine? Are these cards particularly
susceptible to static damage or something? It looks like there's
isolation transformers right behind every BNC connector on these cards
that would keep this sort of thing from being such a problem.

-- 
-Will  :: AD6XL
 Orton :: http://www.loopfree.net/
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