Update: BBC Acorn

From: Joe <rigdonj_at_cfl.rr.com>
Date: Sun Jan 12 17:50:01 2003

  Well the Acorn is alive again. I finally got around to fixing the power supply. That also took care of the buzzing sound that was coming from the speaker. I'm also now getting a prompt. Before the PSU blew I was getting the ROM messages but no prompt. Now I'm getting "Acorn OS", "Acorn DFS", "BASIC" and ">" with a blinking underline prompt after that. However it's still not responding to the keyboard (except for the Control-Break).

  Just for the hell of it I tried powering it up with different ROMs removed. With the "US BASIC" ROM removed it asked "What Language?". Of course since the keyboard wasn't working I couldn't tell it anything. With both the "US BASIC" and "DNFS" ROM removed it reported "View A2.1", "No Text", Editing No File", "Screen Mode 7", "Printer Default" and a "=>" prompt. Looks like I fell into some kind of monitor program. Still can't do anything due to faulty keyboard.

  FWIW the memory chips in it are Mostek 4516N-9.

  I cleaned up before Christmas and misplaced the bag with the screws for it, *&^(&%%!

   Joe

At 10:06 AM 12/13/02 GMT, Pete wrote:
>On Dec 12, 19:43, Joe wrote:
>
>> Nope, all the RAMS are soldered directly to the board and no solder
>flux. I'm sure it was built with 32K and that appears to agree with the US
>model number.
>
>Yes, I'm sure it is, I was just pointing out that in the general case,
>amount of memory is not a good way to tell. AFAIK, Acorn sold only Model
>Bs in the States.
>
>> It's not running at the moment but when it was it said soemthing
>like:
>>
>> "Acron version 2.1
>> DFS OS
>> BASIC OS"
>>
>> There's also a EPROM that says "DFS OS" in it so I think it's supposed
>to say that.
>
>I've not seen a US model start up, but I expect Acorn removed the "BBC
>Microcomputer" part for trademark reasons (in many countries outside the
>UK, BBC is a trademark of Brown Boveri & Cie, and anyway it wouldn't mean
>the same in the States). Presumably they changed the other strings too.
>
>How many (EP)ROMs are in it? Do they have any numbers on them?
>
>> OK thanks for the pointers. I searched the net but found so many
>sites that I haven't had time to go throught them all.
>
>If you're looking for repair information, the ones I listed are good places
>to start. You might also consider joining the BBC mailing list. If you
>want to, send a message with "subscribe bbc-micro" in the body, to
>majordomo at cloud9.co.uk.
>
>> Nope, that's not what I got. It didn't say anything about BBC or
>Microcomputer or the amount of memory and it definitely said "OS" twice. I
>did get the beep then the speaker had a slight buzzing in it. (Possible due
>the the failing capacitor in the PSU). I was in the process of checking
>the PSU outputs for noise when the cap blew. It was quite noticeable!
>
>Maybe they changed the banners more than I thought.
>
>> Actually I didn't get a cursor. I wasn't sure if it was supposed to
>have one or not.
>
>Yes, you should.
>
>> Thanks for the description. That's about what I expected. Sounds like
>I need to find a VIA. I need one for my spares anyway. There are two
>mylar(?) ribbon cables that connect the keyboard to the main circuit board.
>Is the wide one the column inputs and the narrow one the row outputs?
>(Keeping my fingers crossed that it's that simple!)
>
>I doubt if it's that simple. UK models don't use mylar ribbons, they use a
>single 17-way notched IDT cable with a 0.1" pitch, and with a single-row
>Molex IDT header at each end. If the cable is damaged you can use ordinary
>34-way cable with 34-way 2-row IDC headers; just ignore the second row.
> Download the service manual; it has the keyboard diagram, with pinouts.
>
>Fix the PSU first, obviously. The Beeb is a bit choosy about power
>regulation, and if the 5V and 0V connectors (of which there are three
>pairs) don't all make good connections to the board, you can get strange
>faults because the voltage may be too low at some points on the board. The
>red and black wires are +5V and 0V respectively. There's a purple wire for
>-5V, but this is only used for the serial port and audio amp. There's a
>+12V output but only on the AMP connector at the front, as it's only needed
>for peripherals.
>
>
>--
>Pete Peter Turnbull
> Network Manager
> University of York
>
Received on Sun Jan 12 2003 - 17:50:01 GMT