18 Sep
2013
18 Sep
'13
2:18 p.m.
You could also piggy-back a couple of the 7501's to get
by if there were problems.
Dwight
Date: Wed, 18 Sep 2013 21:47:56 +0100
From: pete at dunnington.plus.com
To:
Subject: Re: substituting 7401 for 8881 in a PDP-8/E
On 18/09/2013 20:59, Tony Duell wrote:
I've got more than a tubeful of 7438s but I'd just prefer to use
something that doesn't needs mods if I can. 7439 looks better than an
8881, if I can find any. But it's working at the moment with a 7401,
with seven boards in the machine. I'll add the rest (about nine or ten)
tomorrow and see if it carries on behaving.
I realised the easy way to (ab)use a 7438 is to turn it round 180
degrees (but still the usual way up), and bend out the Vcc and Gnd pins,
which would need swapped.
--
Pete Peter Turnbull
Network Manager
University of York
Anyone
got practical experience of substituting [7401] for an 8881?
I've doen it a few times on Unibus boards and seem to have got away with
it. s you said, the '01 shouldn't be able to sink the current, but at
least soem fothem can.
If you don;t mind swapping pins around, the '38 is not a bad choice
(spec'ed to sink 48mA accorind to the databook I am looking in). It's
easy to find, too...