Date   : Sat, 18 Apr 2009 19:58:00 +0100
From   : mfirth@... (Michael Firth)
Subject: Easter Disaster

----- Original Message ----- 
From: "Alex Taylor" <zeem.uk@...>
To: <bbc-micro@...>
Sent: Saturday, April 18, 2009 7:14 PM
Subject: Re: [BBC-Micro] Easter Disaster


> 2009/4/18 Andy Ford <acorn@...>:
>>
>> The keyboards are different in that a B has a single connection of about
>> 17 pins and the Master has two sets of 15, I am going from memory here
>> so those numbers may not be 100% correct.
>
> There's a place on the Master PCB for a pin header which isn't
> normally fitted. It's just below the keyboard connector and connects
> to many of the same PCB traces. I never noticed it before, until
> someone on the list briefly mentioned its existence, and something
> about its use for connecting up a Model B keyboard.
>
That might have been me - I've commented about it before, but I'm not sure 
if it was on or off list.

If you look at the Master schematic (available on the NVG site), and compare 
the pinout of that header
with the BBC B (or B+) keyboard header, they match pretty much exactly. The 
one difference is that
the cassette motor LED connection is re-used for a battery input connection 
(if I remember correctly)

What I wasn't sure is whether the 3.2 (or 3.5) MOS addressed the keyboard 
the same as the BBC B OS,
and hence whether the other keyboard connector would work.

Experiments in BeebEm show that its Master emulation will work with a 1.2 OS 
ROM, which suggests that
the second keyboard connector on the Master should work.

>> As for length, I'd (guess) you could get away with 30cm (possibly less)
>> without issues. You can use something like an old IDE cable if you
>> needed a length of suitable cable though, saves buying a (possibly)
>> expensive ribbon cable.
>
> I did once use a standard IDE cable when testing a load of hardware on
> a Model B. It meant I could run the machine with the keyboard out of
> the way of the ROMs, so I could test a bunch of them without having to
> move the keyboard out of the way between each operation. I've killed a
> Model B before when doing such a thing loosened the solder joints on
> the keyboard's connector, which after time broke the motherboard.
>
The ACW used a standard BBC B+ motherboard with a remote keyboard on a 
pretty long cable (about 1m
coiled - more stretched). I don't know if the ACW keyboard had extra 
buffering to allow for that, but the ACW
service manual should confirm that (which is available from Chris W's site)

There were also add ons available to convert a BBC B to a two box system 
(pictures of the Viglen one are on
the 8bs site), which again used a standard BBC motherboard and keyboard with 
a longish coiled cable between.

>> I do have a spare complete Master Compact keyboard in my spares,
>> although I am not sure if that would fit a Master or not
>
>> I doubt it due to the extra keys, untested
>> though (no Compact to test it with)
>
> Don't the Master and the Compact have the same keyboard? I've only
> ever seen one Compact in the flesh, that was for sale many years ago
> in a computer shop and I couldn't afford it at the time.
>
I'm afraid I've never seen a Compact in the flesh (except possibly in shops 
when they were new), so can't comment on that.

Regards

Michael