Another Osborne needing TLC

From: Dave Dunfield <>
Date: Sat Nov 6 18:49:14 2004

After the 1A monitor started working, I turned my attention to another
Osborne in need of attention. This is an Osborne-1 - the older one in a
"tan" colored case - not a 1A.

This machine "sort of" works - it powers up, beeps, and displays the
"box" on the screen, along with the "Insert disk in drive A and press
RETURN" message.

At this point however, it seems to keep restarting - the screen continually
clears and redraws the box/message, which creates a flickering effect.

It does not beep as it restarts - experimentation shows that the beep is
enabled at power-up and gets turned OFF by the firmware as part of the init
sequence - it appears the the firmware does not actually turn the beeper ON
at startup, just OFF, so it only beeps after the first power-on (?)

Took it apart and checked all contacts/connections/sockets for corrosion,
reseated everything and still the same operation.

A couple of questions:

1) This machines has a large board on top of the mainboard - this board plugs
   into the Z80 socket (the Z80 moves to the top board), as well as a ROM
   socket and the monitor connector - there is also a bunch of "flying leads"
   which connect to various points on the mainboard and attach to a socket/header
   on the top board...

   Can anyone tell me what this board is? Is it "normal" on an Osborne-1?
   Neither of my 1A's have this board, and the mainboard appears to be the same...
   Is it perhaps an upgrade of some kind?

2) Has anyone disassembled or otherwise obtained source code to the Osborne
   boot ROM - I would like to try and figure out how far the machine is getting,
   and what it is doing when it restarts.

3) Has anyone seen this behaviour in an Osborne before?

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools:
com             Vintage computing equipment collector.
Received on Sat Nov 06 2004 - 18:49:14 GMT

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