Oscilloscope TV line , TV field Trigger mode on Oscilloscopes

Thread Starter

watsongrey

Joined Oct 31, 2014
94
use the Horizontal deflection circuit to also drive the CRT EHT generator,which ,hence became known as a "flyback" supply.

In this Flow chart:
http://en.wikipedia.org/wiki/Analog_television#mediaviewer/File:TV-block-diagram.svg

It only uses the Horizontal blanking signal for the flyback, they don't use the vertical blanking signal for flyback only the horizontal blanking signal

The Flyback circuit is not a power supply, it's just an high voltage AC transformer it says
 

vk6zgo

Joined Jul 21, 2012
677
use the Horizontal deflection circuit to also drive the CRT EHT generator,which ,hence became known as a "flyback" supply.

In this Flow chart:
http://en.wikipedia.org/wiki/Analog_television#mediaviewer/File:TV-block-diagram.svg

It only uses the Horizontal blanking signal for the flyback, they don't use the vertical blanking signal for flyback only the horizontal blanking signal
They don't use horizontal blanking,they use horizontal sync.
The Flyback circuit is not a power supply, it's just an high voltage AC transformer it says
It lies in its teeth!----------The Horizontal deflection circuit has two main functions.
(1) Deflect the beam using magnetic deflection
(2) produce EHT.
Both functions are equally important.

The Horizontal output transformer is also known as the EHT transformer,reflecting both roles.
Stored charge in the magnetic field of the transformer provides part of the current needed to deflect the beam.

It also usually has another "overwind ' on it to produce around 150v Dc supply for the vertical output stage & audio output stage.
There is no "just an high voltage AC transformer" about it!

Googling around,I found this site which has a treasure trove of TV information:-
http://www.epanorama.net/links/videosignal.html
It's a bit nightmarish to navigate,but worth it.
 

vk6zgo

Joined Jul 21, 2012
677
They also insert "vertical interval test signals".

I'm not really sure what VITS signals are used for, they seem to be some kind of code for "transmission testing"

here is the definitions:
a VITS inserter is used to insert the test signal into live programming, so that inline measurements of a transmission chain can be made while the chain is operational.

use the VITS to detect and troubleshoot problems in on-air transmission.
Before the use of VITs,it was necessary to take equipment out of service & perform "full-field video testing",
in other words,send the test signal on all the lines of the field.
VITS may be used to test for correct video amplitude,frequency response,rise time,luma distortion,
colour distortion,& some other tests.

Vertical blanking interval "equalizer test signal"

Equalizer test signals are for to check/test the cable lengths
Yes,I haven't seen a special signal for that,but maybe NTSC uses one.
Long cables may cause a drop off in amplitude/freq response,& equalisers in fixing that may introduce phase errors.
You can test for both.
Do you know what the equalizer signals are for? in the vertical blanking internal

The format of such a signal in 525-line NTSC is:
  • pre-equalizing pulses (6 to start scanning odd lines, 5 to start scanning even lines)
  • long-sync pulses (5 pulses)
  • post-equalizing pulses (5 to start scanning odd lines, 4 to start scanning even lines
It doesn't say much what the pre or post equalizing pulses do or are?
As I heard it,historically,they were to ensure that the vertical sync separator components were always in the same state prior to the beginning & end of the vertical sync pulse proper.
With more modern circuitry they could be reduced in number.
Grey Scale Test signal
I tried a Video Generator set to Grey Scale, and it outputted a 9 step up ramp staircase waveform
I'm guessing the Gray Scale test is to test the Luminance levels and luminance linearity
A waveform monitor is to check the luminance ( brightness ) amplitude levels
A Vectorscope has a Chrominance demodulated IC chip , a Waveform monitor doesn't have this Ic chip built in
Yes,that's what it's for.
You can just look at each step to see if they have the same change in level,or put the signal through a Differentiating Network.
Each step will appear as a spike,with the height proportional to the step increase in level.
Waveform Monitors usually have this function built in.
The Oscilloscopes that have the TV line and TV field , must have that Signal Processor IC chips that seperates the H-sync, V-sync, video signal and the Blanking signal
Or a discrete component circuit to do the same thing.
They don't normally bother with separating blanking,though!


Component video sync:

Separate sync
Uses separate wires for horizontal and vertical synchronization. When used in RGB (i.e. VGA) connections, five separate signals are sent (Red, Green, Blue, Horz. Sync, Vert. Sync).

Composite sync
Combines horizontal and vertical synchronization onto one pair of wires. When used in RGB connections, four separate signals are sent (Red, Green, Blue, Sync).

Sync-on-green (SOG)
Combines composite sync with the green signal in RGB. Only three signals are sent (Red, Green with Sync, Blue). This synchronization system is used in - among other applications - many systems by Silicon Graphics and Sun Microsystems through a DB13W3 connector.

Sync-on-luminance
Similar to sync-on-green, but combines sync with the luminance signal (Y) of a color system such as YPbPr. This is the synchronization system normally used in home theater systems.

Sync-on-composite
The connector carries a standard composite video signal along with the RGB components, for use with devices that cannot process RGB signals. For devices that do understand RGB, the sync component of that composite signal is used along with the color information from the RGB lines. This arrangement is found in the SCART connector in common use in Europe and some other PAL/SECAM areas.[/QUOTE]

Yeah,pretty right.
By the way,I found out that VGA has different scan rates & doesn't use interlaced scans,so iyt doesn't have odd & even fields.
 

Thread Starter

watsongrey

Joined Oct 31, 2014
94
The Tektronix 2467 has a line counter and also the HP 54600 Oscilloscope has a line counter plus TV fields 1 and fields 2 both at the same time can be viewed, plus video triggering options

The Equalizer pulses are to LOCK to the sweep or oscillator of the sync separator chip or Horizontal sweep oscillator

The Sync separator chip has an internal horizontal sweep oscillator

The Vertical rate and Horizontal rate needs to be adjust to LOCK to the sync separator chip's oscillator or sweep frequency
 

vk6zgo

Joined Jul 21, 2012
677
The Tektronix 2467 has a line counter and also the HP 54600 Oscilloscope has a line counter plus TV fields 1 and fields 2 both at the same time can be viewed, plus video triggering options
That's useful,you could look at VITs lines,etc,just like a Waveform Monitor does.
The Equalizer pulses are to LOCK to the sweep or oscillator of the sync separator chip or Horizontal sweep oscillator
Not really,the normal line rate serrations will keep the line Oscilator in step,so the half line intervals provided by equalising pulses are not necessary for that.

The British 405 line system didn't have equalising pulses.

Tying in with my original suggestion,they probably help create a stable trigger point for the vertical triggering.
This helps maintain accurate Interlace timing.
The Sync separator chip has an internal horizontal sweep oscillator
Probably it usually does,but it doesn't have to---discrete circuits provided all these functions separately.
The Vertical rate and Horizontal rate needs to be adjust to LOCK to the sync separator chip's oscillator or sweep frequency
You've got it backwards,but I know what you mean!

The Horizontal & Vertical Oscillators in TV sets are,effectively, Phase Locked Loops,which oscillate at close to the required frequencies even without an external signal.
When they receive syncs from the Sync Separator,they phase (& frequency) lock to that signal.
Some early B & W TVs needed occasional "tweaking" of the "Horizontal Hold" & "Vertical Hold"controls to bring them into range,but more modern designs do not need regular adjustment.

You will find that many Internet descriptions of the operation of TV sets (& many other things,for that matter) are quite superficial,so that your quotes from such sites are only partially correct.

This "statement & refutation" format is getting a bit tiresome,how about phrasing your questions as questions?
 

Thread Starter

watsongrey

Joined Oct 31, 2014
94
So what does the horizontal hold and vertical hold set? the rate of what? they call it "hold" for a reason

The horizontal rate and vertical rate set the resolution
If I speed up or down the Horizontal rate and vertical rate what does this do?

Some Video Test signal generators have a horizontal rate knob output and vertical rate knob outputs
When I adjust the rate knob to speed up or down the horizontal rate and vertical rate it doesn't do anything unless it LOCKS to the sync separator chip or the TV oscillator H-sweep chips & V-sweep chip
 

vk6zgo

Joined Jul 21, 2012
677
So what does the horizontal hold and vertical hold set? the rate of what? they call it "hold" for a reason
It adjusts the H or V oscillator frequency so it is close enough to the correct frequency that it can"lock" to the incoming syncs.
If you have the V control set incorrectly,the picture will "roll" in the vertical direction.
If the H control is set incorrectly,the lines will "break up"rendering the display unusable.
( This latter effect is hard to describe,& needs to be seen)
The horizontal rate and vertical rate set the resolution
If I speed up or down the Horizontal rate and vertical rate what does this do?
They interact to determine the resolution.
The NTSC line system has higher vertical & horizontal rates,than PAL/SECAM,but has poorer resolution.
Why do you think this is so?

Some Video Test signal generators have a horizontal rate knob output and vertical rate knob outputs
When I adjust the rate knob to speed up or down the horizontal rate and vertical rate it doesn't do anything unless it LOCKS to the sync separator chip or the TV oscillator H-sweep chips & V-sweep chip
This is so you can test monitors,etc which operate at different H & V rates.
Broadcast SPGs do not ever change rates,all the equipment must sync to what they generate.
 

Thread Starter

watsongrey

Joined Oct 31, 2014
94
The NTSC line system has higher vertical & horizontal rates,than PAL/SECAM,but has poorer resolution.
Why do you think this is so?


Pal/Secam has higher field rate and frames per second also

On the Tektronix 2476 it has only on the Ch2 is a TV clamp coupling function. The Clamp circuit does something to the Front porch and back porch DC voltage level. When you set the Oscilloscope to AC couple and measure video it says it will distort the video signal. Why does a TV composite signal , RGB component, need a Clamp circuit?

I think a waveform monitor has a Clamp circuit built in to the input channel and also a waveform monitor has a built in line counter. I asked a TV tech and he used a tektronix 465 oscilloscope, took the took the ch2 bnc output signal and feed it to a waveform monitor. I have to say that the tektronix 465 is a really nice scope for delay sweep it just displays really good it's just to bad it doesn't have cursors to do measurements but it's the best scope to do delay sweeping waveforms i think, I think that is why he used it for Video signals. The HP 54600 oscilloscope has a scale option to do IRE or volts.

The VITS signals after the post equalizer pulses is the vertical blanking interval, in this blanking interval they encode water marks , closed caption, text, transmission code, broadcast code. What other types?

This is so you can test monitors,etc which operate at different H & V rates.
Broadcast SPGs do not ever change rates,all the equipment must sync to what they generate.

yes true, so you're saying that NTSC, PAL, SECAM , BETACAM all have the same H& V rates? only VGA has a different H & V rate?

What determines what the is the H & V rate will be? the TV oscillator H & V sweep? the Sync Separator oscillator frequency? what else?
 

vk6zgo

Joined Jul 21, 2012
677
The NTSC line system has higher vertical & horizontal rates,than PAL/SECAM,but has poorer resolution.
Why do you think this is so?


Pal/Secam has higher field rate and frames per second also
Have look at this site:http://www.high-techproductions.com/pal,ntsc.htm
On the Tektronix 2476 it has only on the Ch2 is a TV clamp coupling function. The Clamp circuit does something to the Front porch and back porch DC voltage level. When you set the Oscilloscope to AC couple and measure video it says it will distort the video signal. Why does a TV composite signal , RGB component, need a Clamp circuit?
If a video signal passes through a coupling capacitor the capacitor will cause the loss of the blacking level DC reference,
AC hum pickup on a long video cable can also cause the loss of the blacking level DC reference,
Clamp circuits restore the blacking level DC reference,
I think a waveform monitor has a Clamp circuit built in to the input channel and also a waveform monitor has a built in line counter.
Yes,it does.
I asked a TV tech and he used a tektronix 465 oscilloscope, took the took the ch2 bnc output signal and feed it to a waveform monitor.
He was using the 'scope as a variable gain amplifier to change the level of the signal he was probing to
1.0 volt p-p,so he could use the advanced functions of the waveform monitor.
I have to say that the tektronix 465 is a really nice scope for delay sweep it just displays really good it's just to bad it doesn't have cursors to do measurements but it's the best scope to do delay sweeping waveforms i think, I think that is the blacking level DC reference, why he used it for Video signals. The HP 54600 oscilloscope has a scale option to do IRE or volts.

The VITS signals after the post equalizer pulses is the vertical blanking interval, in this blanking interval they encode water marks , closed caption, text, transmission code, broadcast code. What other types?
Too many to say ---besides I've probably forgotten some of them!
This is so you can test monitors,etc which operate at different H & V rates.
Broadcast SPGs do not ever change rates,all the equipment must sync to what they generate.

yes true, so you're saying that NTSC, PAL, SECAM , BETACAM all have the same H& V rates? only VGA has a different H & V rate?
No.I'm not saying that at all!
BETACAM isn't a System,it is a form of recording,

Standard PAL & SECAM have the same H & V rates.
NTSC's rates are different,
VGA is different again,

Most adjustments on Colour Picture Monitors only require B & W signals.
The variable H& V adjustments on some Test Generators are to enable monitors of various standards to display stable B & W test patterns .
They won't be the correct standard for every case,but will be close enough for adjustment purposes.
What determines what the is the H & V rate will be? the TV oscillator H & V sweep? the Sync Separator oscillator frequency? what else?
The TV or Monitor will normally be synchronised with the sync pulses from the video source.
 
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