Conference netcad::open_decconnect

160.0. "Problem with H4005s" by CHEFS::KERRELLD (To infinity and beyond...) Mon Feb 10 1997 07:21

Can anyone help with this problem a UK DECUS member has with H4005s failing 
:-

"Thanks for your reply.  Our H4005s are all late 1992 vintage, so I guess we
can asssume it's not a batch problem.  Given that all our failures are recent,
and seem to be getting closer together, we're working on the possibilities of
electrical problems on our network. 

Since the terminators have not been damaged we assume the AUI side of the
transceiver is what's failing and the transceiver isolates the thickwire
cable.  The first one to go did actually catch fire (burst electrolytic
capacitor, charred transformer board) so whatever's happenning seems to be
dramatic, but somehow the driving devices (2 separate DELNIS, a DECServer 100,
and a MicroVAX 3100) suffer no ill effects.

I think we need to know more about the hardware so we can try to work out what
electrical faults we need to look for.  On the H4005 the electrical tolerances
and design info (a circuit schematic ?) might help us figure out what did the
damage without affecting anything else, and for the ethernet some information
about earth voltage differences, ripple voltage tolerance and so on may help.
If you know of anyone who could help obtain this information or already knows
what we ought to be looking for, perhaps you could pass our request on to
them.

By the way, we are working on the basis that the failures are not caused by
simple ageing (because the failures have started suddenly and are bunched
together, and the first failure was so dramatic!), but we might be 
wrong(?)."


Thanks,
Dave.