HP "calculators" (was Re: World's first computer on ebay!)
ard at p850ug1.demon.co.uk
Tue Apr 17 15:22:21 CDT 2007
> At 20:02 -0500 4/14/07, ard wrote:
> >It puzzles me too. The connector in question is a normal, double-sided 25
> >pin (per side) 0.156" pitch edge connector. That's actually not a common
> >size in the UK (0.156" pitch is not normally used over here), so it's
> >probably somebody 'borrowed' it becuase it was the easiest way to get
> >that sort of connector.
> Is there any chance that the connector was removed because it was
> causing some sort of mechanical interference or stress on the board?
> Just guessing wildly, but maybe, if it was otherwise
I cna't see how...
The I/O backplane is a little board, about 5" square. It contains 4 edge
connectors only (no other componets, not even decoupling capacitors), and
has edge fingers along the bottom edge that fit into a simialr connector
on the main backplane (the large PCB, also jsut connectors, that's flat
in the vottom of the machine).
In this cae, somebody careffully desoldered the second-from-top connector
on the backoplane. I assume they needed the connector for soemthing --
otherwiswe qwhy not just whip out the complete I/O backplane if it was
causing problems (the machine will run without it).
I suppose a previous owner might have had a Peripheral Control ROM and
used interfaces with this machine (and this was later separated from the
machine), and that one connector on the I/O backplane might have become
damaged and, say, been shorting a couple of lines together so it had to
I guess I'll never know (and I don't really need to know -- I just need
to get the replacement connector and solder it in).
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