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Old 10th Mar 2024, 12:03 am   #81
bobbyball
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Default Re: Television Magazine Testcard Generator

That's really good!
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Old 12th Mar 2024, 9:27 pm   #82
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Default Re: Television Magazine Testcard Generator

Quote:
Originally Posted by bobbyball View Post
That's really good!
Thanks!

I've just built the alternative circuit to generate the green square using a couple of 74LS221s in place of the four 74121s and this is also working well.

I am going to attempt replacing most of the original 74xx ICs with 74LSxx types plus some further circuit improvements. I will look at first simplifying the clock circuits for the line and field waveforms. Then look at the gating circuits which will be extended for the additional add on patterns.

This project has been ongoing for about two years and I've learnt a great deal from it and enjoyed experimenting with it. As it has been a long project and I don't have the room for it in my workshop, it's been set up in a spare bedroom so that I can come back to it when time permits.
What has really surprised me is the fact that this complex circuit (46 ICs in the original design) works at all on a breadboard layout. The whole thing is quite complicated together with all the extra add ons so far.
Further work is being done on other PAL coders to assess the best one for the finished project.

Please see a few pics of the temporary breadboard test circuits.
In the first pic the two green square generator circuits. The upper using the 74LS221s and the lower one using 74121s.
In pic2 an overview of the project build so far.
Pic 3 shows three different PAL coders including the original TBA520/TBA540 one.
I will post the circuit diagrams in due course.

Regards,
Symon
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Old 12th Mar 2024, 10:13 pm   #83
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Default Re: Television Magazine Testcard Generator

. . .My efforts with them myself in my student days when I was learning my TV theory shows just how uncritical Malcolm Burrell's circuits were, and still, are!

Apart from the video and the PAL encoder, all the patterns are equivalent to fairly low audio frequencies or low r.f. only (the highest frequency resolvable in 625 line video is 5.25 MHz), apart from the frequencies involved for a "multiburst" pattern, the effects of stray capacitances and inductances are, for the most part, negligible, so any reasonable layout will work, even breadboards work as Symon has proved!

The main stumbling block, ideally, is to use a PAL encoder that avoids the use of that pesky 270 ns Philips delay line or awkward inductors!

. . .Frank Cuffe has offered some extremely valuable assistance in working out the decimal numbers for programming an EPROM to give the circle – see the thread I started entitled "PM5544 Unit 2 Circle Memory Programming" for details!

. . .At the moment I'm trying to work out how the special "DEM", "DELAY" and "MATRIX" patterns are encoded, and it's not proving an easy job trying to extract the information from the PM5508 manual!

. . .A chap has provided a PCB and source code for controlling up to 24 relays by means of a rotary encoder with an LCD character module interface, originally intended for Bob Cordell's THD Analyser, so it will (hopefully!) be possible to adapt this for pattern control with relay pattern selection – I've got the PCBs and two micros and I'm studying the source code at the moment!

Chris Williams
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Old 12th Mar 2024, 10:32 pm   #84
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Default Re: Television Magazine Testcard Generator

Hi Chris.

I look forward to seeing your circle generator circuits using an EPROM. I haven't yet had the time to do any work on the circle pattern. I also hope to start doing some EPROM experiments for my pattern generator circuits in due course.

I still haven't completed the LM1889/LM1886 coder circuit but it looks a reasonable alternative to the Mullard circuits. The TEA1002 or TEA2000 coders are good options but lack the input capability for the R-Y and B-Y colour difference signals.

Re the 270ns luminance delay line. I think it should be possible to make one using fixed inductors. In one of the BATC PAL coder circuits there was such a circuit.

Regards,
Symon
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Old 13th Mar 2024, 5:11 pm   #85
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Default Re: Television Magazine Testcard Generator

Afternoon Symon!

. . .Work on designing a PM5544 Unit 2 Circle Memory PCB is now in progress!

. . .In the Original Philips PM5544 Unit 2 Circle Memory Circuit the EPROM is permanently enabled but I see no reason why a "Circle On/Off" switch or jumper link and pull–up resistor can't easily be added to the EPROM's "/OE" pin if need be!

Chris Williams
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Old 22nd Apr 2024, 9:56 pm   #86
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Default Re: Television Magazine Testcard Generator

. . .My work to develop the following boards is still in progress:–

a) A Philips "DEM", "MATRIX" and "PHASE" board ;

b) A method of adding the PM5544 Coloured Brackets and the "Anti–PAL" colourless areas to the T.C.G. pattern!

The principle used in the PM5544 is to allocate "H" and "V" coordinates to each PM5544 square and then derive enabling pulses from these co–ordinates which are then used to enable signals from the RGB matrix that correspond to each particular section of "bracket colour" and the "colourless Anti–PAL" areas, so the work involved is :–

i) Calculating the timing of the H and V co–ordinate pulses ;

ii) Working out the exact matrix proportions for each colour!

Chris Williams
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Last edited by Chris55000; 22nd Apr 2024 at 10:08 pm.
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Old 22nd Apr 2024, 10:34 pm   #87
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. . .The principle used in the PM5544 Generator is to define each vertical and horizontal of each of the PM5544's cells with a "H" and a "V" co–ordinate, and then calculate the timing of the enabling pulses by means of the appropriate division ratios using counters triggered by the end of the blanking at the beginning of the active line/field and reset at the end of each line/field.

Exactly the same principle can be added to Malcolm Burrell's T.C.G., as follows :–

a) Ignoring the half–height squares immediately below the top border and above the bottom border, we have a matrix of 140 full–size squares, let the top left square be H1V1 and the bottom right square be H14V10, so we need a counter to divide by 14 triggered by the end of the left hand border and reset at the start of the right–hand border, defining 13 lines along the distance covered by squares H1V1 to H14V1, plus a field–rate counter dividing by 10, triggered by the end of the top border and reset by the beginning of the bottom border.

If, therefore, we want the two squares H1V1 and H1V2 to have "G–Y=0 at 146°", we AND–gate the "Binary 2" o/p and "binary 1, binary 4 and binary 8 outputs inverted" of the verticals counter and also with the first cycle of the field–rate horizontals counter with the R, G and B feeds to the resistor matrix defining "G–Y=0 at 146°", and feed this gated output to the video summing point, the effect will be to colour H1V1 and H2V1 squares with "G–Y=0 at 146°".

It's a difficult concept to grasp but studying the PM5544 S.M. will indicate how it is done!

Chris Williams
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Old 23rd Apr 2024, 12:54 pm   #88
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Default Re: Television Magazine Testcard Generator

Hi Chris, Symon.

I have a project on the go that needs NTSC signals. The AD724 kit that I used previously is no longer available so I have just done the artwork for a PAL or NTSC version and ordered suitable NTSC crystals and chips from China. MOQ for boards is 10 so I will have some spares.
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Old 23rd Apr 2024, 10:12 pm   #89
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Default Re: Television Magazine Testcard Generator

Hi Trevor.

Thanks for that, I'll send you a PM tomorrow.

Regards,
Symon
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Old 5th May 2024, 12:17 pm   #90
Chris55000
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Default Re: Television Magazine Testcard Generator

For reference, I have appended the "Easy PC" circuit diagram of the B.A.T.C. Pal Coder I am currently laying out a replacement PCB for!

Chris Williams
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Old 5th May 2024, 12:52 pm   #91
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Default Re: Television Magazine Testcard Generator

Re-posted as the circuit has a mistake in the labelling - please use this one!

Chris Williams
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Old 5th May 2024, 4:47 pm   #92
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Default Re: Television Magazine Testcard Generator

Quote:
Originally Posted by Philips210 View Post
Quote:
Originally Posted by bobbyball View Post
That's really good!
Thanks!

I've just built the alternative circuit to generate the green square using a couple of 74LS221s in place of the four 74121s and this is also working well.

I am going to attempt replacing most of the original 74xx ICs with 74LSxx types plus some further circuit improvements. I will look at first simplifying the clock circuits for the line and field waveforms. Then look at the gating circuits which will be extended for the additional add on patterns.

This project has been ongoing for about two years and I've learnt a great deal from it and enjoyed experimenting with it. As it has been a long project and I don't have the room for it in my workshop, it's been set up in a spare bedroom so that I can come back to it when time permits.
What has really surprised me is the fact that this complex circuit (46 ICs in the original design) works at all on a breadboard layout. The whole thing is quite complicated together with all the extra add ons so far.
Further work is being done on other PAL coders to assess the best one for the finished project.

Please see a few pics of the temporary breadboard test circuits.
In the first pic the two green square generator circuits. The upper using the 74LS221s and the lower one using 74121s.
In pic2 an overview of the project build so far.
Pic 3 shows three different PAL coders including the original TBA520/TBA540 one.
I will post the circuit diagrams in due course.

Regards,
Symon
Now that is a test pattern generator. Respect!
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Old 6th May 2024, 8:40 pm   #93
Philips210
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Default Re: Television Magazine Testcard Generator

Quote:
Originally Posted by inaxeon View Post

Now that is a test pattern generator. Respect!
Thank you inaxeon. Much of the credit should go to Malcolm Burrell. Although there are a number of flaws in the design, his project was interesting to me. I remember back in the early 1980s looking at the circuit but was put off by the complexity and also the cost of the ZNA134E sync/blanking generator chip. I can't recall any other magazine project that published a colour test card built from TTL ICs. Plenty of pattern generators yes, and test cards based on EPROMs etc but not colour test cards built from TTL.

It must be about twenty years ago that I won a few ZNA134E chips on eBay for a very good price. Forum member Trevor (SeeMos) kindly sent me many pics of his complete unit which was of great help for making corrections to the original circuit diagram. Having the ZNA134 chips and Trevor's pics finally gave me the enthusiasm to make a start on project.
My work on the project has mainly involved making refinements to the test card particularly the border castellations. A fair amount of work has also gone into testing alternative PAL encoder circuits and this work continues.
I am also considering adding the special colour patterns to the test card which will be challenging.
Besides the test card, and for versatility, I intend having available many individual test patterns.

Once I've gone as far as I can go with the project, I'm thinking about a complete redesign along the lines of the ETP-1 pattern but with a circle.
I've learnt a great deal with this project and I am still learning. I like building and testing circuits. TTL circuits seem durable and forgiving if you make a few mistakes give or take.

Regards,
Symon
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Old 6th May 2024, 8:57 pm   #94
Philips210
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Default Re: Television Magazine Testcard Generator

Quote:
Originally Posted by Chris55000 View Post
Re-posted as the circuit has a mistake in the labelling - please use this one!

Chris Williams
Thank you Chris for your work on this encoder circuit diagram. This TBA520 based encoder will be useful when experimenting with the the colour difference signals.
I intend building this circuit which is somewhat more refined than the original encoder. It's superior in the subcarrier generator, matrixing, burst gating and output filtering so I'm hoping for good results from it.

Regards,
Symon
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Old 7th May 2024, 10:30 am   #95
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Default Re: Television Magazine Testcard Generator

. . . There are still one or two little "howlers" I accidentally left on my diagram :–

I) C20 should have it's positive side connected to R72/R73 base potential–divider for TR12 base ;

ii) TR6 in the composite video amplifier (top right–hand corner of page) should have been marked as TR12 – I forgot to amend it when copying the symbol !

iii) The plug pins of PL1 to PL7 need re–designating – I'll do this when I update my component Library !

. . .Once I've completed my PCB design for this to my complete satisfaction, a full circuit diagram, board layout, parts–list and setting–up information will be posted – the board is 80% done on a Eurocard size PCB !

Chris Williams
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Old 7th May 2024, 12:15 pm   #96
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Default Re: Television Magazine Testcard Generator

For maximum brownie points in the next version, how about VITS on the appropriate lines in the vertical blanking interval?

I remember seeing a Tek VM700 for sale on an amateur radio rally stall in the past few years. They weren't asking much. The chap on the stall didn't know what it did.

David
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Old 7th May 2024, 6:31 pm   #97
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Default Re: Television Magazine Testcard Generator

. . .That's not an impossible task, it's just a matter of counting the appropriate line by means of a "line selector circuit" – Television Magazine published such, so I'll study the circuit and work out how to gate the selected line with the o/p from the pulse–and–bar board!

Chris Williams
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Old 7th May 2024, 8:54 pm   #98
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Default Re: Television Magazine Testcard Generator

I recently scanned the manual for an 80's era VITS generator:

https://github.com/inaxeon/PTV_Prese...654_Manual.pdf

Has loads of information about VITS within.
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Old 8th May 2024, 7:06 pm   #99
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Default Re: Television Magazine Testcard Generator

Quote:
Originally Posted by Radio Wrangler View Post
For maximum brownie points in the next version, how about VITS on the appropriate lines in the vertical blanking interval?

I remember seeing a Tek VM700 for sale on an amateur radio rally stall in the past few years. They weren't asking much. The chap on the stall didn't know what it did.

David
Hi David,

Yes a good addition to the test pattern generator. Again, that will be a challenge for me to understand and implement the pattern. I have been reading up on the pulse and bar pattern. Located at the top of the screen in the field blanking interval together with the teletext data. These signals were often seem as visible interference at the top of the picture sometimes due to a slower than required field flyback in some TVs.

Regards,
Symon
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Old 8th May 2024, 7:30 pm   #100
Philips210
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Default Re: Television Magazine Testcard Generator

Quote:
Originally Posted by inaxeon View Post
I recently scanned the manual for an 80's era VITS generator:

https://github.com/inaxeon/PTV_Prese...654_Manual.pdf

Has loads of information about VITS within.
Hi inaxeon

Thanks, but I can't access the pdf. I'm getting a message "Unable to render code block".

Regards,
Symon
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