At 2011-05-05 1:48 pm Paul Jeroni wrote in sci.electronics.repair,
"You must connect the shields, the waveforms on the scope are all
noise."

OK. With the shield of the scope lead connected to the shield of
composite output on the Armada, these are the signals while the
BIOS setup is running and when X is running in Linux.
http://members.shaw.ca/peasthope/ArmadaBIOS.jpg
http://members.shaw.ca/peasthope/ArmadaWithX.jpg

Two details. Normally the Armada is not grounded.
The external power supply has a ground pin on the plug but,
as I understand, the DC output is isolated. Secondly, the
composite signal is very jumpy. The two traces were taken
using the digital storage capability of the scope.

In these images, the big wave is the vertical refresh and the
horizontal sweep isn't resolved at this speed of the scope? So
what can be done to dissect the composite signal enough to see
why the BIOS gives an image on the TV and X does not?

I haven't ruled out use of Windows and Powerstrip as suggested
by Adrian C. Just want to apply the scope effectively as a
first step.

Thanks, ... Peter E.

BIOS is usually at 640x480 but Windows sets it much higher.

I do video for a living and I have no idea what those scope traces
are.

G²

On Sep 8, 9:10*pm, wrote:
BIOS is usually at 640x480 but Windows sets it much higher.

It was back in 2011-03 or so that I connected the Panasonic TV
to the Armada and have forgotten some details. I did set X to
640x480 and find the display on the TV still not resolved.

How closely is the composite signal tied to the built-in video on
a laptop? I wonder whether software can control composite
output independently of *VGA. Even so I'd wonder what X could do
to make the TV image fail.

I do video for a living and I have no idea what those scope traces
are.

The sweep is set at 1 ms and trigger coupling is to TV-H. How
do you connect a scope to the composite output on a computer
and what is the usual display?

Thanks, ... Peter E.
peasthope.at.shaw.ca

On Sep 9, 9:25*am, Peter Easthope wrote:
On Sep 8, 9:10*pm, wrote:

BIOS is usually at 640x480 but Windows sets it much higher.

It was back in 2011-03 or so that I connected the Panasonic TV
to the Armada and have forgotten some details. *I did set X to
640x480 and find the display on the TV still not resolved.

How closely is the composite signal tied to the built-in video on
a laptop? *I wonder whether software can control composite
output independently of *VGA. *Even so I'd wonder what X could do
to make the TV image fail.

I do video for a living and I have no idea what those scope
traces
are.

The sweep is set at 1 ms and trigger coupling is to TV-H. *How
do you connect a scope to the composite output on a computer
and what is the usual display?

Thanks, * * * * * * * * * * * *... Peter E.
peasthope.at.shaw.ca

I hunted up the Compaq Armada docs from HP and they are not really
clear on the TV output. They say the unit puts out composite TV. Here
is a link to a Tektronix page showing SMPTE NTSC color bars on a
waveform scope. The amplitude is 1 Volt p-p into a 75 Ohm termination.
Amplitude is typically 2 Volts without the termination. Bandwidth is
4.5 MHz for standard def. Line length from H sync to H sync 63.56 uS

http://www.tek.com/Measurement/App_N...fmmonitor.html

The actual picture on the monitor of SMPTE bars

http://en.wikipedia.org/wiki/File:SMPTE_Color_Bars.svg

BTW no standard def monitor ever looked exactly like that Wiki
picture. If you made that image full screen your scope should look
like the Tek waveform scope.

Since they say the output is composite I assume the connector is an
RCA but nowhere do they ever show the connector, just the closed door
on the front of the computer.

G²

On Sep 9, 8:32*pm, wrote:
I hunted up the Compaq Armada docs from HP and they are not really
clear on the TV output. They say the unit puts out composite TV.

Yes.

Here is a link to a Tektronix page showing SMPTE NTSC color bars on a
waveform scope. The amplitude is 1 Volt p-p into a 75 Ohm termination.
Amplitude is typically 2 Volts without the termination. Bandwidth is
4.5 MHz for standard def. Line length from H sync to H sync 63.56 uS

Thanks. I have only a plain old BK Precision 2522 Digital Storage
Oscilloscope.
No waveform monitor. The photos I posted are just the raw video going
to the
BK 2522. Without the demodulation capability of a waveform monitor,
an
oscilloscope can not display color bars. The BK 2522 might do a
little more
in this case but I have yet to learn the skills.

Thanks, ... Peter E.

On Sep 14, 7:31*am, Peter Easthope wrote:
On Sep 9, 8:32*pm, wrote:

I hunted up the Compaq Armada docs from HP and they are not
really
clear on the TV output. They say the unit puts out composite TV.

Yes.

Here is a link to a Tektronix page showing SMPTE NTSC color bars
on a
waveform scope. The amplitude is 1 Volt p-p into a 75 Ohm
termination.
Amplitude is typically 2 Volts without the termination. Bandwidth
is
4.5 MHz for standard def. Line length from H sync to H sync 63.56
uS

Thanks. *I have only a plain old BK Precision 2522 Digital Storage
Oscilloscope.
No waveform monitor. *The photos I posted are just the raw video
going
to the
BK 2522. *Without the demodulation capability of a waveform
monitor,
an
oscilloscope can not display color bars. *The BK 2522 might do a
little more
in this case but I have yet to learn the skills.

Thanks, * * * * * * * * * * * *... Peter E.

A waveform monitor is nothing more than a specialized scope with
preselected gains and sweep rates and a graticle in IRE units
vertically and uS horizontally rather than cm.. Your scope (and my old
Tek 475) will be just fine. I wanted you to see what the video
waveform should look like and Tektronix has excellent info on TV. The
vector scope is a different animal and is not needed for now but by
probing the chroma demodulators in a monitor could you display vectors
on your scope as well.

Bottom line: if you displayed color bars on the Compaq the scope photo
from Tek will be close to what you see on your scope once you get the
sweep and gains set up. The trickiest part of TV is triggering the
scope but many scopes have a TV mode to make it easier.

G²

On Sep 14, 8:33*am, wrote:
Bottom line: if you displayed color bars on the Compaq the scope photo
from Tek will be close to what you see on your scope once you get the
sweep and gains set up. The trickiest part of TV is triggering the
scope but many scopes have a TV mode to make it easier.

OK. The manual is with the B&K scope here. When there is a quiet
afternoon I'll work on it again.

Thanks! ... Peter E.