SUN Networking problems - test-drb@ccmp.vtda.org

22 Mar 2001

Peter Turnbull wrote:
...
 It sounds like you've shorted the cable. Do those
transceivers have a set
of LEDs on them? I suspect not, but that might tell you if anything is >being
transmitted/received.

The InterGraph transceivers have three LEDs labeled PWR, SQE and COL while
the NV1000 only has one located next to the AUI connector. It's been quite
some time since the error happened and I've forgotten how they behaved, but I'll
re-try and watch 'em this weekend.

...
 You could try removing one terminator and testing the
DC resistance
between core and shield of the coax; it should be 50 ohms with nothing >powered up.
If you have shorted it...

OK, I tested with my DMM and there was a reading of 51,4 Ohms on it - I
guess that's inside the tolerance and not to be called a short...

Tony Duell wrote:
...
  we've put
another transceiver on the cable strictly according to the
installation guide that came with it (drilling hole into cable with
recommended tool etc...).
Since we've done that, it's no longer possible to print from one of the
SUNs to the CalComp although the PC is not yet connected to the
transceiver. THis may be something that has been mangled by the translation into
English, but I want to get it right : Can you print from one of the Suns
and not from the other, Or Can neither Sun print? 
Yes, it was a bit of a strange translation (my fault...) but the meaning is
the following: One SUN only can't print while the other one cannot be tested
as it doesn't boot up due to internal data loss in the battery buffered RAM. 

...
 ...I would suspect either damage to one of the
transceivers (was the network powered up when you drilled the cable?...

No, we had powered down everything and even disconnected the drop cables
...
 from all units on the network before drilling the tap
hole. 
...
 ...or maybe a reflection from the 'stub' caused
by the new transceiver (did you follow all the rules about unequal spacing of the
transceivers, etc?

There are several black marks on the yellow cable and when we got it, we
were told if we ever were going to add another transceiver, we should put it
next to one of those marks. And so we did. But as there seem to be rather
complicated rules for working out this, I'd like to know them in order to check if
the markings on the cable show the correct places.

Thank you all for your suggestions on finding the problem.

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