Date   : Tue, 20 Sep 2005 10:05:18 +0100
From   : Richard Gellman <splodge@...>
Subject: Re: Poorly Master?

Adam D. Barratt wrote:

>Hi,
>
>I've recently acquired a Master 128 which is exhibiting some slightly
>odd symptoms. I've had a look through the list archives but can't see
>anything that obviously explains the problems. Sorry if this is a bit
>long, but I've tried to include as much information as I could think
>of / remember how to gather (it's been a few years since I last owned a
>Beeb).
>
>*TIME / TIME$ return gibberish, so my first thought was that the CMOS
>battery was flat. However, as I understand it, setting TIME$ should give
>a useful *TIME output, at least until the machine is powered off.
>
>Unfortunately, this is what happens:
>
>  > *TIME
>      ,00 Xx 1922.23:12:06
>  >TIME$="Mon,08 May 1900 12:00:00"
>  > *TIME
>      ,00 Xx 1922.23:12:49
>  
>
Interesting to note 22.23:12 (10110, 10111, and 01100 ) in binary. Could 
be metallic fluff on the CMOS bus pins (the CMOS chip uses a combined 
address/data bus with a bus select line)?

>*HELP hangs, although not always. From power-up, *HELP gets as far as
>SRAM and then stops with a flashing cursor and the shift lock led
>illuminated; hitting escape drops back to the prompt as expected and
>shift lock led goes out again. *HELP SRAM works fine, *HELP MOS also
>hangs, three or four lines from the end of the output. (Update - the
>hangs only occur if the startup mode is 7/135 - after a *CONF. MODE 128
>both are quite happy).
>  
>
I'd like a double-check on this, but I think this is by design. Its not 
locked, but rather letting you read it. Try hitting shift to "release" 
it. If it works, then there's no problem. The only thing that niggles me 
is that I'm sure it normally does it at a point other than SRAM. The 
reason it doesn't happen in Mode 128 (shadow mode 0) is because there 
are more lines (32 instead of 25) - i.e. *HELP fits on the screen, so no 
need to pause while you read it.

>The disc drive activity light is illuminated from power-up, and the
>drive makes clicking sounds as soon as a disk is inserted and the door
>secured - both No Directory and No Boot are set. I've tried several
>disks which should work (although they've been in a box for several
>years) and can't persuade the drive to catalogue any of them.
>  
>
Hmm. This is looking like a general fault in the bottom left corner of 
the board (where the System VIA, 1770 FDC and CMOS chip lie). Closer 
inspection thereof may reveal clues. If your VIA chips are removable 
(rare, but some boards have this) see if swapping the VIA chips around 
has any interesting effects.

>I've tried resetting the CMOS, followed by setting Lang to 12 and
>Floppy, but all of the symptoms still occur as described. Any
>suggestions as to what might be wrong, where to look for further clues
>would be most welcome. If there's any other information you might need
>to suggest either of these then I'll retrieve them as any when.
>
>  
>
-- Richard