-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Wednesday, 28 October 1998 14:19
Subject: Re: Microvaxen bits etc.
>Oh well... Another useful product becomes unavailable thanks to progress...
>
Seems that way. I may have found a source of new ones, but the price is a
bit much.
S/H ones seem to disappear as soon as they come out of service.
>> Most network cards produced these days don't have AUI ports on them.
>Yes, a lot of them are 10 base T only. Even though (IMHO) 10 base 2 makes
>more sense for a small home network (no need to have a hub) and BNC plugs
>are a lot easier to wire than those RJ45 things.
Oh, RJ45's are no problem provided you have a decent tool. I use crimp on
BNC's as
well. I have a mix of both on my home network and at my shop. The school
is all cat 5 now.
>Fortunately, I got a load of transceivers at a radio rally with minor
>faults (mostly open-circuit connections on the BNC connector).
Lucky boy.
>If there's a 16 pin chip near the BNC connector marked 83C92 or something
>like that, then it can be made into a transceiver. You can either raid
>the bits off the card or (Hey, a good idea...):
>A lot of cards have 6 links that you have to move to select between AUI
>and 10 base 2. They simply link the appropriate signals from the logic on
>the card either to the AUI connector or to the internal transceiver. It
>should be possible to feed signal from an AUI 'input' to the right pins
>on those links, apply power (you probably only need the +12V line) to the
>card and avoid a lot of work.
<GRIN> Actually, this thought also crossed my mind whilst gazing at just
such a card.
I'm going to try that. I have an NE2000 clone card I'm going to try and
convert to a txcvr.
I think it needs +-12v and +- 5v, but that's not a big problem. (Diskless
workstation PSU)
>If you want to try this, then you'll need to trace out the schematic
>around the links. It's worth knowing that most of the pulse transformers
>used to isolate the logic signals at the transceiver contain 3 little
>transformers in a 16 pin DIL package on pins (1,2,15,16), (5,6,12,13),
>(7,8,9,10).
Yep, can see them.
>Trace the secondaries to the transceiver chip and then you
>know what each transformer section is for (one will be Tx Data, one
>RxData, one Collision). Alternatively, trace the link connections to the
>ethernet chip on the card, but it may be more difficult to get data on
>that.
Not even gonna try. A direct patch into the txcvr from the AUI port with a
little xover cabling ought to do it.
> Did I mention that you'll need the data sheets on the transceiver chip?
You did. Know a source? Online one preferably?
>The pinout is :
<snip>
Got it, thanks for that.
>> connect them.
>
>The cable is special :-(. It's 4 twisted pairs + shields (which you link
>to the ground pins). One of the twisted pairs is thicker than the other
>3, and is used for power.
I imagine most anything will probably work, provided the leads are kept
short.
I have some shielded audio stuff that should do nicely.
Something to experiment and tinker with for a while. :^)
Cheers
Geoff Roberts
Computer Systems Manager
Saint Marks College
Port Pirie South Australia.
My ICQ# is 1970476
Ph. 61-411-623-978 (Mobile)
61-8-8633-0619 (Home)
61-8-8633-8834 (Work-Direct)
61-8-8633-0104 (Fax)
Received on Wed Oct 28 1998 - 01:14:36 GMT