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Re: I could use a hand locating hardware bits and pieces and/or technical documentation for repair.

Newsgroups	comp.sys.3b1
Date	2016-03-05 19:08 -0800
References	<11f11849-2c2c-433a-ad2f-555403129d14@googlegroups.com> <d8b7a9bc-21b3-4631-9c2a-a6c33afd166f@googlegroups.com> <slrnndkjrv.bs4.BPdnicholsBP@Katana.d-and-d.com>
Message-ID	<3d6fddd8-7124-4cd5-8c92-b0c30fefa122@googlegroups.com> (permalink)
Subject	Re: I could use a hand locating hardware bits and pieces and/or technical documentation for repair.
From	300wattwarlock@gmail.com

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On Friday, March 4, 2016 at 9:17:12 PM UTC-6, DoN. Nichols wrote:
> On 2016-03-05, Chris Smith <protheus@byteorder.net> wrote:

> > The Burroughs/Unisys keyboard, once open, starts looking a _whole_ lot
> > like the AT&T one.  Based on continuity tests at the plugs (which are
> > also 8 pins) I find that three of them are connected together and two of
> > the others are connected together, leaving three other lines.  It would
> > make a whole lot of sense for these to be negative, +5v, and (rx, tx,
> > rst) respectively, exactly as in the other keyboard.
> 
> 	Agreed -- with likely "negative" ('ground') as the three wires,
> and the +5V being the two together.  But verify this with the original
> keyboard plugged into the computer -- don't go by what I guess is
> correct. :-)

I'll poke around a bit at it next week hopefully.  This is true of the Unix PC keyboard.  I can't plug the other one in since I don't currently have the computer for it.  :)

> > wondering how difficult it would be to just wire it in and try it.
> > Perhaps not much.
> 
> 	What are the connectors like on the new keyboard?  If something
> other than the one for the 3B1, I would suggest making an adaptor rather
> than modifying the cable.  This could make it easier to swap wires
> around at need.)

That's the plan.  I believe the connector is something called sdl.  The old pc keyboard used a six pin connector to hook the cable up to the keyboard.  This one uses an 8 pin one.  It's something like a modular plug with contact edges along the top, but also a shielded shell.  It's flatter and wider than an RJ, with catches on the sides instead of on the bottom.  I'm not absolutely sure of this but I can order a couple of the connectors and try it.  Not yet sure how I'll get them crimped on to a cable, though.  I don't have the original cable that went to the computer, but in pictures they look D-shaped on the system end.

> > Interestingly, when the bad keyboard is plugged into the machine with
> > a mouse on the other side, the mouse works fine.  This suggests to me
> > that there must be some logic in there that's working properly.  Perhaps
> > whatever runs the keyboard matrix is the only thing that's not
> > functional.
> 
> 	I *think* that 5V, ground, and the txd are simply routed through
> the keyboard.  Maybe the reset, too.  I've never tried holding down a
> key for repeats while moving the mouse to see whether they interfere
> with each other.

How would that work if there's only one data line going out of the keyboard?  I mean, wouldn't there be some multiplexing going on in there, or am I missing something?  Or maybe you mean tx from the computer into the keyboard...?  That would make some sense.

Chris

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