Date   : Wed, 10 Nov 2010 02:12:35 +0100
From   : rick@... (Rick Murray)
Subject: BBC B micro repairs

On 09/11/2010 17:29, J.G.Harston wrote:

> You keep contradicting yourself:
> "I removed everything except MOS and BASIC"
> "As soon as I put any ROM chips in..."

Indeed. I think, reading between the lines - he has MOS and BASIC in, 
and the problem manifests putting *another* ROM in. But this is my own 
guess, for the report does indeed contradict itself.


The problem we have here is there's a selection of ROMs to choose from 
(they can't all be dead, right) and three ROM sockets (they can't all be 
dead without the likelihood of affecting the other (MOS/BASIC) ROMs.


Thus:

 > That is, you will be testing something like:
 > empty empty empty BASIC
 > empty empty BASIC empty
 > empty BASIC empty empty
 > BASIC empty empty empty

This is the absolute first thing to do. Rule out a faulty ROM socket 
and/or address decoding problems.

[PS: JGH, do I get points for debugging? Line 3, BASIC listed twice! (I
      have corrected this one to make it clearer)]



Please PLEASE *P*L*E*A*S*E* post your status at each stage doing only 
*ONE* thing at a time. How the hell are we supposed to narrow down a 
problem with a message that reads "I did this and this and this and 
this...".



So. BASIC in each slot, starting from the right, with MOS in the left 
slot as normal.
Result is?

[if the above failed at any point, STOP, post what happened, ignore the 
stuff below]



Put BASIC in the rightmost slot and DFS in any other slot.
Result is?



If it fails, leave BASIC alone and try a different slot.
Result is?



If it fails, remove DFS and put Wordwise in the SAME slot as DFS was in.
Result is?



Can you access/start up Wordwise...
Result is?




It may seem boring and tedious, and I think I know the answers to most 
of these questions, but we need to know *exactly* what does and does not 
work.



> I'm extrapolating to assuming that the ringing program is in ROM,
       ^^^^^^^^^^^^^
Same problem see? ;-)


 From an earlier message:
--8<--------
I then put them all back (except the ROMS) and it still seemed to be
working. However, when I put ROMS in, it goes back to the flashing
cursor, and no "Basic" on the screen. I've tried moving the "Basic"
chip" but it makes no difference. I've changed the BASIC chip (and the
OS chip), with no difference.
The Watford DFS chip says "Watford DFS" on the screen and has a
flashing cursor below it, so you can't type anything.

My ringing program it does not see at all, but has a flashing cursor.

I tried a Wordwise chip, and that goes straight into Wordwise when you
turn on, and you can't get out of it. Control/Break just brings up
Wordwise again. *Quit gives the message: "Bad Command".
--8<--------

It seems quite interesting to me that BASIC *appears* to fail, yet 
Wordwise works. Could it be that the keyboard has been wired to attempt 
to boot from the floppy and this is what is causing some of the problem?

Will the MOS hang forever on a Shift-Break situation, or would this 
eventually time out?


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...