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Re: Composite video from Compaq Armada e500.

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.

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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.

Reply to
Peter Easthope
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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.

G=B2

Reply to
stratus46

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.

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

Reply to
Peter Easthope

On Sep 9, 9:25=A0am, Peter Easthope wrote: > On Sep 8, 9:10=A0pm, snipped-for-privacy@yahoo.com 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. 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

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The actual picture on the monitor of SMPTE bars

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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.

G=B2

Reply to
stratus46

Yes.

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.

Reply to
Peter Easthope

On Sep 14, 7:31=A0am, Peter Easthope wrote: > On Sep 9, 8:32=A0pm, snipped-for-privacy@yahoo.com wrote: >

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.

G=B2

Reply to
stratus46

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.

Reply to
Peter Easthope

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