28 Sep
2014
28 Sep
'14
9:26 p.m.
From: David Riley
I think most if not all Qbus backplanes were PCBs. But
some of them
(notably the H9270) are PCBs with wire-wrap posts for the connector
terminals. Makes it very handy to, say, modify the H9270 for 22-bit,
which I did .. with no problem.
This reminds me of something I'm looking into. I have a BA11-N (Q18/CD) which
I'd like to upgrade to BA11-S (Q22/CD). (Yes, yes, I know, the -S has a
oomphier power supply, which I won't have, but I'm not trying to run a lot of
power-hungry cards.)
I've tried finding an H9276-A backplane (Q22/CD) to go in it, to replace its
existing H9273-A (Q18/CD), but _every_ place I called which had one listed
reasonably cheap (<$100), and which claimed their internal stock database
(i.e. not just their lame, useless, Web-site) showed they had one... when they
checked the actual shelf, they did not in fact have any.
So now I'm thinking, maybe I'll just add the BDAL19-22 lines to the existing
H9273-A. It doesn't have wirewrap pins, but there's enough pin showing that I
can get two wires onto each pin, and solder them; does not look to be
difficult at all.
I have verified that the CD part of the backplane is identical in both (the
1983-84 Microcomputer Interfaces Handbook, EB-23144-18, has pinouts for the CD
part for both, and they are indeed identical). Alas, I cannot find detailed
data on the rest of the H9273-A: neither the BA11-N Technical Manual, nor the
Print Set, is available online. (I found some old list email which indicates
that someone named David Powell had a copy of the TM - does anyone know him?)
So, has anyone tried to upgrade an H9273-A to H9276-A, and are there any
pitfalls? From what I can see, there shouldn't be a problem, but I'd like
to be 100% sure before I start plugging cards into it...
Noel