Osborne One -- No video.

From: Feldman, Robert <Robert_Feldman_at_jdedwards.com>
Date: Tue Jul 17 09:04:10 2001

I have an Osborne I Technical Reference manual, ut it is a bit skimpy on the
video (no circuit diagrams, for example). It does provide a pinout for the
video connector. The signals come from the bottom and the shunt carries them
to the top, where they go to a single inline connector that connects to the
monitor. Looking at the edge connector from the front (numbered right to
left, odd on top, even on the bottom), the signals are:

2 Ground
4 Brightness High
6 Brightness Low
8 Brightness Arm
10 Ground
12 Horizontal sync
14 +12V
16 Video out
18 Vertical sync
20 Ground

The shunt just connects the top contact to its mate on the bottom: 1 to 2, 3
to 4, etc.

The inline connector pinout is

1 Horizontal Ground
2 Brightness High
3 Brightness Low
4 Brightness Arm
5 Ground
6 Horizontal sync
7 +12V
8 Video out
9 Vertical sync
10 Video Ground

First thing to check is to make sure that you are getting +12V on contac1 14
of the circuit board and pin 7 of the inline connector.

The Brightness High, low and arm go to a 100K pot (arm to the wiper). Line 8
(video goes to a 500K pot connected to 10 (video ground).

The manual notes: "Warning: The video connectors contain TTL-level signals
along with +12 Volts, and are quite vulnerable to damage by accidental
misconnections."

As to the RCA socket, I had a Tan case Osborne I, and I do not remember that
it had a composite video connector. You needed an adaptor (about
1.5"x1.5"x0.75" that plugged on the edge connector in place of the shunt.
One brand was Exmon (sp?), as another poster mentioned. I saw something that
looked like one at a surplus electronics website a few months ago. I don't
recall which, but I will try to find it again.

You should see the big Osborne "O" logo and ROM version info when you turn
the computer on. There was no special keystroke combination to switch to
external monitor. I forget what the 52/80/102 character display switch was,
but I think that was through software. The higher video resolutions required
a daughter board, which was a later addition on my tan-case O1.

-----Original Message-----
From: Rich Beaudry [mailto:r_beaudry_at_hotmail.com]
Sent: Tuesday, July 17, 2001 7:59 AM
To: classiccmp_at_classiccmp.org
Subject: RE: Osborne One -- No video.


Hello all,

To answer the replies so far....

1) There is a small black connector labeled "Do no remove when power is on"
or something to that effect. I does indeed cover a card-edge style
connector. I did remove it, power OFF, and I didn't recall it had anything
conductive inside. It just looked like a plastic plug. I'll have to look
again, when I go home this evening...

2) I did try the composite video output. Nothing there, either.

3) As I stated before, there was no light from the CRT at all, after taking
the cover off and powering up. I will perform the ohmmeter test suggested
by Dave McGuire tonight.

- As for the composite video connector... Does anyone know if there is any
magic keystroke or other setting to enable this? Perhaps if the internal
monitor is dead, I can still use an external one...
Received on Tue Jul 17 2001 - 09:04:10 BST