Date   : Tue, 09 Nov 2010 16:29:03 +0000
From   : jgh@... (J.G.Harston)
Subject: BBC B micro repairs

Alan Griffin wrote:
> As instructed, I removed the chips, and all the ROM chips except for
> the OS and Basic chips.
> I put all the other chips back in, and it seemed to be working normally.
> As soon as I put any ROM program chip in, such as the Watford drive, or
> Wordwise, or my bell-ringing program, things go wrong.

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

> The Watford DFS gives the double bleep and displays "Watford DFS on the
> screen, with a flashing cursor, and ignores the keyboard.
> Wordwise runs "Wordwise" and you can't get out of it, even with *QUIT
> which it does not recognise.
> My ringing program gives a double bleep, with "Basic" on the screen and
> reacts to the keyboard, but no mention of the program and it says "Not
> found" with a Control/Break.

I'm extrapolating to assuming that the ringing program is in ROM, otherwise
with DFS not working how are you loading it.

The "Not found" error is coming from ROMFS looking for a !Boot file, which
indicates that no other filing system has started (eg in your case WDFS).
It looks like either the WDFS ROM has gone faulty or the disk controller
hardware.

*QUIT giving an error is also indicative of DFS not starting up, as *QUIT
is not an inbuilt command, it is trying to run it from the filing system
and tape/rom is saying it doesn't exist. I presume *QUIT is a program on
disk supplied to you for your purposes.

Can you get out of Wordwise with *BASIC ?

I'm not sure what you mean by "My ringing program gives a double bleep,
with "Basic" on the screen". Do you mean that with BASIC and the ringing
ROM both plugged in, the computer boots up to BASIC?

 From what you've descibed so far, is sounds like all the non-ROM chips
are ok, the machine stops working as you add extra ROMs. What happens
if you just have BASIC, then just BASIC, WDFS, then just BASIC, Wordwise,
then just BASIC, Ringing, and in combination of sockets?

It's sounding more and more to me that either disk disk controller
is faulty, or the disk drive/lead/power/etc.

I earlier typed the following, which may be irrelevant if you've
already done this:

Ok, with just MOS and BASIC plugged in and various other chips
unplugged, you say it boots to Basic. Can you type anything?
If you can, insert the non-ROM chips one by one, turning the
computer back on after each one and see if you get to Basic
and can type things. Report back what chip you inserted which
caused the computer to stop working.

(You could use a binary search to do this faster)

If you get everything plugged in and still works, booting to
Basic, you can type things in, then that suggests something
wrong with one of the ROMs or ROM sockets.

Still only keeping MOS and BASIC, move BASIC sequentially
into each of the other three ROM sockets. If the computer
fails to start, hanging saying "Language?", that indicates
that the socket you're testing is faulty.

If all four ROM sockets work, it suggests a faulty ROM.

Put BASIC back in it's original socket. Go through your
other ROMs one at a time. For each ROM plug it into each
of the three remaining sockets and see what happens.

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

empty empty WWISE BASIC
empty WWISE empty BASIC
WWISE empty empty BASIC

empty empty WDFS BASIC
empty WDFS empty BASIC
WDFS empty empty BASIC

That should have identified a faulty ROM or socket by now.

-- 
J.G.Harston - jgh@...