HP "calculators" (was Re: World's first computer on ebay!)

Tony Duell 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 
> non-functional....?

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 
be removeed

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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