Osbourne 1 problems

From: Feldman, Robert <Robert_Feldman_at_jdedwards.com>
Date: Mon Oct 14 16:54:01 2002

I have an O1 Tech Ref manual, from which I can send you info that might be
useful. I'm busy this week, so won't be until next, though.

One thing to check is the video shunt on the front of the unit. It takes the
video signals and power from the bottom of the board and passes them to the
top, where they go to the monitor. If the contacts on the shunt are
oxidized, you could have video problems.

The pinout of the edge connector is (numbered right to left, odd on top,
even on bottom):

(19 ... 1)
(20 ... 2)

2 Ground
4 Brightness High ---> 3 on top
6 Brightness Low ---> 5 on top
8 Brightness Arm ---> 7 on top
10 Ground
12 Horiz Sync
14 +12 volts
16 Video Out
18 Vert Sync
20 Ground

3 and 7 go to the outsides of a 100K brightness pot, 5 to the wiper of the
pot.

Video out and one of the grounds go to a 500 ohm contrast pot.

Bob

-----Original Message-----
From: Sark [mailto:ian_primus_at_yahoo.com]
Sent: Monday, October 14, 2002 2:08 PM
To: cctech_at_classiccmp.org
Subject: Osbourne 1 problems


I recently accquired an Osbourne 1 computer. I turned it on and it
seemed to work, I was able to boot BASIC off of a floppy and I wrote a
couple little programs, (print hello world, count to ten, and count
forever, stuff like that). The picture on the screen was kinda dark in
spots, and while the computer was counting, it flickered to a very dark
and barely readable, then it went black all together. I tried turning
up the brightness and contrast controls, the only one that makes any
change on the screen is the brightness control. I can see the rasters
when the brightness is up all the way, but the contrast control has no
effect. The computer seems to still work though, I can turn it on, then
hit enter and it will boot from the floppy. Previously, when it was
working, I noticed the screen flicker when the computer accessed the
floppy drive. My guess is that there is something wrong with the power
supply. Does anyone have any ideas? I would really like to get my
Osbourne working again, it's a really cool little computer.

Thanks!

Ian Primus
ian_primus_at_yahoo.com
Received on Mon Oct 14 2002 - 16:54:01 BST