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Video Pattern Generator

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Junior Member level 3
Apr 12, 2001
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video pattern generator

Video Pattern Generator with PIC16F84 and MC1377

video pattern generator circuit

This TV Pattern Generator has failures in sync timing. It does not comply to PAL standard (jitter on fields). But on most TV receivers it does not make problems.

pal generator

Borber said:
This TV Pattern Generator has failures in sync timing. It does not comply to PAL standard (jitter on fields). But on most TV receivers it does not make problems.

It seems to be a circuit to generate PAL-N signal. PAL-N (mainly used in Argentina) has an NTSC-like subcarrier frequency. Used on a normal PAL tv or monitor, there will be no color at all. Changing the subcarrier frequency will effectively solve the problem.

The PAL-N and PAL-BGHI may have slight difference in the sync length, burst position and start/end of video, but there are large tolerances which will effectively make no difference at all on any tv/monitor.

Just make sure the burst frequency is set according to your tv -> otherwise, no color!

My two cents...


Dear TurboPc
it seems that you havent understood what is the problem. It is not the colour subcarrier but sync timing. That is something absolutelly different.
As I can analyse the signal something is wrong in second field timing.
Instrument like WM700 simply reports Sync is missing.

ad725 circuit

Sorry Border,

I did not know you tried the circuit. I just looked at the documents and everything was looking OK. My comments were only to pinpoint the differences between PAL-N and PAL-BGHI.

BTW, do you have the fix in gicapa's code? Is the missing sync pulse in the serration, half lines or other lines?

Thanks for the info.

mc1377 pic

Hi TurboPC
I just could'nt find out what is vrong. When signal is connected to Tektronix Monitor it shows jittering in the top 20% of picture. When looking at the vertical sync pulses they jiter regarding the field. Some jitter is present in line synchronisation but less then in vertical interval. It seems that pll in horizontal synchronisation of monitor is reducing it a bit.
I do not have suitable oscilloscope to be able to examine problem in details.

tektronix wm700

What IC can replace MC1377.
Please help.

mc1377 generator

I used AD724 from Analog. They send samples.

video pattern generator schematics

you also have ad723 and ad725 from the same analog...

video generator pic16f84

Here is another circuit for a simple dot cross hatch pattern generator. I got it off the net sometime ago. I do not have the link. I hope someone will find it useful.

circuit video pattern generator

I have a problem with the 1st PAL generator(pic16f84&MC1377). There is a burst in the output signal, but the picture is in black and white. There is no oscillation on the crystal 4.43MHz. I tried to adjust the capacitator trimer, but no result :|

pal video pattern generator pic

i have rgb signals and sync pulses
can you help me by giving circuit of encoding the signals by using ad725

ad723 ad725 difference

i am using ad725. i am not able to find osci. of 17.73445Mhz.can anybody give me idea?
and if i do not use crystal will it give signal which can be used for black and white tv?

pal generator mhz

Regarding subcarrier crystal you may use one of two other crystals (4.43361MHz and 8.86723MHz) together with frequency quadrupled or doubler. They are used in TV sets and probably you will find them.
Using ordinary LC oscillator instead of crystal will be satisfactory for B/W but not for colour signal.

video pattern generators

Hi, I've built it, with MC1377,4.43361MHz quartz,added video modulator from old video.R15 at the emmiter of the output is 75 oms.Here is another pattern generator.I've used the pic part from it together with MC1377.It has more options.

tv pattern generator schematic

have used AD725 instead of MC1377.
AD725 gives output 2V peak-peak at 75 ohm output impedance. I want it to convert it into the 1V p-p at 75 ohm output impedance.
can u help me?
I do now want to use only 5V supply

ad725 16 bit color

OK. Video level must be always measured on output terminated with 75Ω and not without load. 2Vpp is normal for unterminated output.
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