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How to verify a stable video signal ( NTSC / AV )

B

Boki

Jan 1, 1970
0
Hi All,

My Video ( NTSC ) output (AV) seems not stable, when I keep a static
picture there, I can see the picture is flashing ( something like the
backlight flashing, about 10Hz...measured by my eyes.. )

How to check the video signal is stable or not?

Want to make sure that is power problem or circuit protect problem....


Best regards,
Boki.
 
M

martin griffith

Jan 1, 1970
0
Hi All,

My Video ( NTSC ) output (AV) seems not stable, when I keep a static
picture there, I can see the picture is flashing ( something like the
backlight flashing, about 10Hz...measured by my eyes.. )

How to check the video signal is stable or not?

Want to make sure that is power problem or circuit protect problem....


Best regards,
Boki.
Down load the NTSC timing specifications, and check your signal with a
scope, quite often published in philips semiconductor video IC specs,
it sounds as if you have a major timing problem

Get a proper TV signal from a TV tuner, and lock your oscilliscope to
that, put your AV signal on the scope and see how quickly it drifts
across the screen , or hire a Tektronixs(sp?) wavefrom monitor




martin
 
J

John O'Flaherty

Jan 1, 1970
0
Boki said:
Hi All,

My Video ( NTSC ) output (AV) seems not stable, when I keep a static
picture there, I can see the picture is flashing ( something like the
backlight flashing, about 10Hz...measured by my eyes.. )

How to check the video signal is stable or not?

Want to make sure that is power problem or circuit protect problem....

Maybe something is running at 50Hz vs 60Hz, or the other way.
 
L

Luhan

Jan 1, 1970
0
Boki said:
Hi All,

My Video ( NTSC ) output (AV) seems not stable, when I keep a static
picture there, I can see the picture is flashing ( something like the
backlight flashing, about 10Hz...measured by my eyes.. )

How to check the video signal is stable or not?

Want to make sure that is power problem or circuit protect problem....


Best regards,
Boki.

This sounds like a problem witht the monitor. The video signal itself
is probably not the problem. I had a Radio Shack TV/Monitor that used
to do this.

Luhan
 
M

martin griffith

Jan 1, 1970
0
Down load the NTSC timing specifications, and check your signal with a
scope, quite often published in philips semiconductor video IC specs,
it sounds as if you have a major timing problem

Get a proper TV signal from a TV tuner, and lock your oscilliscope to
that, put your AV signal on the scope and see how quickly it drifts
across the screen , or hire a Tektronixs(sp?) wavefrom monitor




martin
Dammit, misread the OP, I thought Boki had created a video signal with
a micro or some such evil device, and had problems with the signal


martin
 
R

Rich Grise

Jan 1, 1970
0
Hi All,

My Video ( NTSC ) output (AV) seems not stable, when I keep a static
picture there, I can see the picture is flashing ( something like the
backlight flashing, about 10Hz...measured by my eyes.. )
About 10 HZ sounds like you're seeing a beat between the power line and
the vertical oscillator. Check the power supply for ripple.
How to check the video signal is stable or not?
Oscilloscope.


Want to make sure that is power problem or circuit protect problem....

With your scope, look at the video itself - I've seen scopes that
have "TV V" and "TV H" horiz. sweep settings; one syncs up to the
vertical, the other to the horizontal, so you can see a side view
of the frame or a top view of the lines. ;-) Any instability should
show up there.

Also, use the scope to check for ripple in the DC, both in the video
source (although, if that were the case, you'd have seen it on the
video itself) and in the monitor.

If they're all OK, I'd start looking for an interconnect problem,
and so on.

Good Luck!
Rich
 
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