14 Jun
2015
14 Jun
'15
11:52 a.m.
I have a DEC distribution panel and internal cable. The panel has a circuit breaker, a 15
pin D connector on the outer side for the transceiver, and another 15 pin D connector on
the inner side for the internal cable between the DELUA card and the distribution panel.
The back of the 730 chassis does not have an open slot for the Ethernet transceiver, as
all of the other slots are already occupied. A bracket for the Ethernet bulkhead panel is
screwed to one of the rack's rear panel brackets. Whoever routed the internal round
cable before I got the machine did a less than perfect job, so it kept getting snagged
when sliding the 730 chassis in and out. The cable jacket has many nicks, but they do not
appear to penetrate the conductor jackets.
I've just tried reinstalling it, and things aren't moving smoothly yet. I
don't think that round cable behaves properly in the flat cable flex area, so next I
will see if I can find a clean path between the card cage and a different area of the
chassis where I can route it along the gantry that supports the power inlet cable. The
round cable just doesn't route as cleanly as the original bundle of flat cables, so
I'll need to fiddle and cuss until I get it working well.
Once I manage to route the internal cable, I'll plug in a DEC AUI cable to the
bulkhead panel, and a DEC 10baseT transceiver, and see if I can get networking up.
The first time I started playing with VAXen as a student, there was generally a long AUI
cable running to a vampire tap on thick yellow coax. Sometimes the coax was routed through
the building, and occasionally there would be a vampire tap down in the stem tunnels with
an AUI cable extending into a subbasement. I've never installed a vampire tap myself.
Then a couple years later at a different university, most of the easily accessible wiring
was thin coax, and 10baseT was still newfangled.
On Jun 14, 2015, at 11:27, Johnny Billquist <bqt at
update.uu.se> wrote:
On 2015-06-14 19:25, Mark J. Blair wrote:
What happened to the original cable and distribution panel?
As a warning - the original distribution panel have a fuse for the 15-pin Dsub, to avoid
excessive power use on the connector. If you go directly from the board to a transciever,
you might run the risk of damaging the DELUA itself if something goes wrong.
Put another way. The design is to have an internal cable from the DELUA to a distribution
panel at the back of the machine. There you have the 15 pin AUI connector, which have a
fuse. You then had an external AUI cable from there to your transciever, which
traditionally sat on a thick coax. Of course, later on, you started having thin ethernet.
Still AUI cable and transciever, though. Eventually twisted pair showed up. But you had
transcievers for that as well. And if you have room behind the machine, you could connect
the thin ethernet or twisted pair transscievers directly to the distribution panel
connector, so no actual external cable.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol On Jun 14, 2015, at 10:01, tony duell <ard at
p850ug1.demon.co.uk> wrote:
If the connector on the DELUA board is a normal Berg-type header (and I think it is) then
maybe you could
use a piece of (twist-n-flat?) ribbon cable to make an extension that could be routed
through the cable
pan arrangement and then connected to the original DELUA cable back in the rack cabinet.
That might be a good approach. The DELUA end of the cable has a Berg connector, and the
other end has the typical 15-pin D-sub AUI connector with a slide latch. I'll look up
the cable wiring to see if signals that would best be twisted pairs are conveniently
placed on adjacent odd/even pins, such that twisted pair ribbon cable would work well
electrically.
Or maybe I can use the round cable that I already have, with P-shaped cable clamps
screwed down using the screws at one end of the flat cable clamps. There may not be enough
clearance in the tray for that.