Date   : Fri, 14 Aug 2009 22:44:01 +0100
From   : philb@... (Phil Blundell)
Subject: econet bridge protocol

On Fri, 2009-08-14 at 22:33 +0200, Anders Carlsson wrote:
> In addition, neither Digi-Key, Mouser nor Jameco has the AM26LS34 but
> other chips in the same series. However a crude Google search suggests
> there are plenty of sites where you could ask for a quote but it
> doesn't mean they can source them.

There are certainly plenty of distributors around who specialise in
stocking obsolete/surplus parts, and I imagine it would be easy enough
to find someone who has the 26LS34 in stock.  But most of those guys
tend to have a minimum order charge of $100 or so which is clearly no
good if you just want a couple of line receivers.

On the other hand, there are a few other Beeb-related ICs that are
becoming difficult to buy and, if you could find a distributor who
stocked enough of them, it might be worthwhile for somebody to order a
bunch of assorted components and then re-sell them to individuals.  An
opportunity for the BeebShop, perhaps.

Looking at the SN75175 datasheet again, I now see that it isn't quite as
compatible with the 26LS34 as I'd first thought: one of the enable pins
is inverted on the '34.  So, to make the '175 work correctly I think you
would need to bend pin 12 out of the socket and tie it to +5V.
Pragmatically speaking that might still be the easiest way to get the
bridge working in short order.

p.