Re: Building a monitor tester?

Hi Rodger!

A looked into using a soundcard as a vector generator a couple of years ago.

The problems I found were the same that you mentioned, no Z channel, no DC
coupling and too slow for true a true VG.

The Asteroids digital VG uses a sample rate of 6mhz, most soundcard peak at
48khz (a high end card might go up to 96khz).

I did do a web search then and found at least one person drawing simple figure 8
type patterns on a scope using a sound card.

If you just wanted to write test patterns, that might work. You would not draw
one point at a time, instead send the trace to the ends of the screen and let
the audio filters fill in the rest. I'm thinking the traces might not be very
straight though, without DC coupling, and distortions from the audio bandpass
filter limits. Might not be very useful for convergence tests, etc.

-Zonn

On Tue, 27 Feb 2001 13:50:06 -0600, Rodger Boots <rlboots@cedar-rapids.net>
wrote:

>I was at my Real Job last night and all of a sudden something dawned on
>me. Couldn't someone take an old, cheap laptop computer and make a
>universal arcade monitor tester out of it?
>
>The raster side should be easy enough, just get the machine to get the
>sync speeds right. For most arcade monitors you could use a computer
>CGA mode.
>
>As for vector monitors, the scanning could possibly be done by recording
>a test pattern from an actual video game USING THE SOUND CARD of the
>computer. Then edit the resulting wave file into a loop. When played
>back the card SHOULD (in theory anyway) reproduce the test pattern.
>
>There are some gotchas involved, though.
> 1) Sound board input and output must be DC coupled or the result
>will have some
> interesting distortions.
> 2) No decent way to handle video (Z channel). This could
>eventually be added,
> but in simple example above it won't exist.
>
>But on the plus side at least the volume control on the computer can be
>used to adjust picture size. Granted, a small plus side, but I'll take
>any plusses I can get.
>
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Received on Tue Feb 27 20:00:52 2001