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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	2016-03-08 12:28 -0800
References	<11f11849-2c2c-433a-ad2f-555403129d14@googlegroups.com> <d8b7a9bc-21b3-4631-9c2a-a6c33afd166f@googlegroups.com> <slrnndkjrv.bs4.BPdnicholsBP@Katana.d-and-d.com> <3d6fddd8-7124-4cd5-8c92-b0c30fefa122@googlegroups.com> <slrnndq0k3.srn.BPdnicholsBP@Katana.d-and-d.com>
Message-ID	<063e5509-b1d1-46cd-bd3e-96b93d20964e@googlegroups.com> (permalink)
Subject	Re: I could use a hand locating hardware bits and pieces and/or technical documentation for repair.
From	Chris Smith <protheus@byteorder.net>

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On Sunday, March 6, 2016 at 10:25:12 PM UTC-6, DoN. Nichols wrote:

> > 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.  :)

> 	O.K.  I've gone to _The Reference Manual_, and found that the
> serial chip for the keyboard is on sheet 14 of the system board
> schematics.  It gives the following pin functions:
> 
> KBDTXD	--> JK-7
> GROUND	--> JK-1,2,3
> +5V	--> JK-4,8
> KBDRST	--> JK-5
> KBDRD	<-- JK-6
> Chassis Ground to  JK-shield
> 
> with "JK" being the jack on the system board into which the keyboard
> plugs.

Thanks.  It's good to have this from a somewhat authoritative source, and it agrees with what I've found so far.

> 	At a guess it is something like this:
> 
>  5 6 7 8
>  : : : :
>  1 2 3 4
> 
> Making the GROUNDs a row along one side (bottom as I show it here, but
> check which three are shorts together -- perhaps examine the underside
> of the keyboard PC board under the connectors) and the +5V is the two
> together at the end past the GROUND pins.  That would make the KBDRST
> the one adjacent to the first ground pin, the KBDRD the middle of the
> three, and the KBDTXD adjacent to one of the +5V pins.

Not looking at it just now, but yes it's something very much like that.  The grounds are a row and the +5v lines are a column on one side, leaving RST and the tx/rx pair in one corner of the connector.

> > 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.
> 
> 	So -- this is a female connector on the keyboard itself, instead
> of on a cable.

Unfortunately so. :)

> 	I'm thinking that the transmit bursts are short enough (high
> baud rate) so the chances of a collision with the mouse signals is
> minimal.  Perhaps the mouse signal is sent through a gate which is
> turned off when the keyboard is about to transmit a keystroke.  (Likely
> turned off just long enough before so a mouse signal could complete or
> time out before the keyboard character or characters were sent.)
> 
> 	Anyway -- you should expect the keyboard end of the 3B1 cable to
> be the same as the computer end -- no crossing of pins between the ends.

Previous experiments also show this to be the case.

Chris

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