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Old 24th Jan 2024, 8:07 am   #1
inaxeon
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Default Attempting to modify a UK PAL TV for PAL-M

yes, this is a weird thing to be attempting ...

I have a newer vintage Trinitron TV which has a MC44002 colour processor / MC44140 delay line.

The datasheets for these chips mention PAL-M but no example is given how to deploy it. I swapped the NTSC crystal for a PAL-M equivalent, which got the colour decoding, but something isn't right.

The MC44002 is sending the MC44140 the correct signal to select PAL decoding (0v) but it there are errors in the test pattern. Some of the colours are "stripy", as are parts of the Anti-PAL areas. It's almost like it's (sort-of) still in NTSC decode mode? Or perhaps something is out of adjustment, but this arrangement looks to be quite fixed i.e. nothing to actually adjust?

Just looking for ideas about what to attempt to investigate...

Cheers
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Old 24th Jan 2024, 12:13 pm   #2
SteveCG
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Default Re: Attempting to modify a UK PAL TV for PAL-M

I'm not familiar with this set, but a question you might check upon is this: Is the line frequency for PAL-M exactly the same as for PAL-I? If it is not then the delay line value would need to altered to that appropriate for PAL-M. Do I recollect correctly that Brazil used PAL-M?
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Old 24th Jan 2024, 12:33 pm   #3
inaxeon
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Quote:
Originally Posted by SteveCG View Post
I'm not familiar with this set, but a question you might check upon is this: Is the line frequency for PAL-M exactly the same as for PAL-I? If it is not then the delay line value would need to altered to that appropriate for PAL-M. Do I recollect correctly that Brazil used PAL-M?
It was just Brazil, yes. It shouldn't matter too much about the set specifically, I'm just trying to understand what considerations may exist around this kind of conversion and this is a good thought!

I guess it would be wise to try work out how to test the delay line, and if it is doing the right thing...
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Old 24th Jan 2024, 5:15 pm   #4
Mr Hoover
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Here are some specs on the different systems.

https://en.m.wikipedia.org/wiki/PAL

You could try generating a Pal N signal (625 line version of Pal M basically) and
see if the received picture looks better, the delay line in the set should be correct
for that
Pal N was used in Argentina mainly.
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Old 24th Jan 2024, 6:56 pm   #5
inaxeon
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Default Re: Attempting to modify a UK PAL TV for PAL-M

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Originally Posted by Mr Hoover View Post
Here are some specs on the different systems.

https://en.m.wikipedia.org/wiki/PAL

You could try generating a Pal N signal (625 line version of Pal M basically) and
see if the received picture looks better, the delay line in the set should be correct
for that
Pal N was used in Argentina mainly.
I don't have anything which generates PAL-N unfortunately. That would be interesting!

Have spent a few more hours diagnosing. The delay line appears to be working exactly as expected. Beginning to suspect that something is wrong in the colour difference / matrix stage.

I've even had an I2C analyser hooked up to the chroma processor to see what is being written to its registers, even that hasn't turned up anything obvious, so far it all appears to be configured correctly. Dang this is tricky!
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Old 24th Jan 2024, 7:20 pm   #6
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Default Re: Attempting to modify a UK PAL TV for PAL-M

The 64 uS delay line won't be quite right on 525 lines.
Line frequency is 15,734 Hz for Pal M, same as NTSC, fractionally different to
625/50 15,625 Hz.
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Old 24th Jan 2024, 7:35 pm   #7
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Default Re: Attempting to modify a UK PAL TV for PAL-M

There's some quite good technical info for the MC44002 in Motorola's datasheet https://pdf1.alldatasheet.com/datash...A/MC44002.html. Not sure if it will give you the right answer but worth a look for the various applications of this IC.

Regards,
Symon
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Old 24th Jan 2024, 11:16 pm   #8
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Default Re: Attempting to modify a UK PAL TV for PAL-M

To process System M PAL the MC44002 should have a 14.3Mhz crystal connected to pin 32 of that IC. For 625 line PAL a 17.7Mhz crystal is connected to pin 33. The sub-carriers operate at 4fsc.
The system is controlled by a sand-castle pulse which is connected to pin 4 of the MC44140. See attachments.
The System Selection Signal to pin 5 of the MC44140 has four levels and is used to command the functioning the NTSC,PAL and NTSC SECAM 1 and SECAM 2.

DFWB.
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Old 25th Jan 2024, 7:30 am   #9
inaxeon
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Default Re: Attempting to modify a UK PAL TV for PAL-M

After a lot more investigation, I have spotted something rather interesting. Attached a couple of scope captures of the output of the MC44002 before it goes into the MC44140 delay line:

PURPLE: Colour bar generator output
YELLOW: MC44002 R-Y Output (Pin 37)
BLUE: MC44002 B-Y Output (Pin 36)

The way the chroma processor is decoding PAL-M vs PAL(G) is completely different. For PAL-M it comes up with a different result for each line, but for PAL-G it is (almost) the same. This would explain the mess. You can't do PAL if your odd/even decoded difference signals are entirely different!

But I don't yet understand what is going on here.
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Old 25th Jan 2024, 8:24 pm   #10
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Default Re: Attempting to modify a UK PAL TV for PAL-M

When I was at Philips, we had lots of people asking about different standards. Some sets just switched automatically, others needed 'help'. The ones that needed help required a few component changes.....resistors, capacitors, sometimes a different delay line depending on the decoder chip fitted. It might be worth finding a data sheet for the decoder chip to see if anything else is required.
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Old 25th Jan 2024, 8:39 pm   #11
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Quote:
Originally Posted by Sideband View Post
It might be worth finding a data sheet for the decoder chip to see if anything else is required.
I did actually provide a link to it in post #7.

Regards,
Symon
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Old 26th Jan 2024, 1:21 pm   #12
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Hi to all,
Hi inaxeon,

From page 37 of the MC44002 pdf (Thanks! Philips210) you can read this:

"The MC44002/7 could also be used for the PAL M and N standards that are used in some parts of South America, but because the subcarrier frequencies differ by some kHz from the normal, crystals with a different center frequency would be required."

Which i understand as this 40 page pdf makes no effort to actually use this IC to work on "weird" versions of the PAL system (M & N).

Maybe a crystal of 3x or 4x the PAL-M subcarrier frequency quoted as 3.575611 MHz in the WikiPedia article is required for proper PAL-M decoding.
Just a suggestion...

Best Regards
jhalphen
Paris/France
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Old 26th Jan 2024, 3:03 pm   #13
inaxeon
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Quote:
Originally Posted by jhalphen View Post
Hi to all,
Hi inaxeon,

From page 37 of the MC44002 pdf (Thanks! Philips210) you can read this:

"The MC44002/7 could also be used for the PAL M and N standards that are used in some parts of South America, but because the subcarrier frequencies differ by some kHz from the normal, crystals with a different center frequency would be required."

Which i understand as this 40 page pdf makes no effort to actually use this IC to work on "weird" versions of the PAL system (M & N).

Maybe a crystal of 3x or 4x the PAL-M subcarrier frequency quoted as 3.575611 MHz in the WikiPedia article is required for proper PAL-M decoding.
Just a suggestion...

Best Regards
jhalphen
Paris/France
Installing a 14.30244 MHz crystal is one of the first things I did (it came from Brazil). Yes the datasheet is annoying. It basically says it can do PAL-M, but then gives no example of how to do it.

I'm presently attempting to modify a standalone NTSC decoder for PAL-M to see if I can learn anything from that process.
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Old 26th Jan 2024, 3:50 pm   #14
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Hi to all,
Hi inaxeon,

Thanks! for the reply.

There was a discussion on VideoKarma mid-2023 about PAL-M, standard PAL & NTSC initiated by a chap in Brazil. Some products, decoding ICs, etc. come up in the thread, might make interesting reading for you :

http://www.videokarma.org/showthread.php?t=275886

Best Regards
jhalphen
Paris/France
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Old 27th Jan 2024, 10:44 am   #15
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Just a thought: Are you sure that your source of PAL-M is actually producing a correct signal? You have not mentioned what it is.

Last edited by SteveCG; 27th Jan 2024 at 10:45 am. Reason: typo
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Old 27th Jan 2024, 11:22 am   #16
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Default Re: Attempting to modify a UK PAL TV for PAL-M

there is a big clue in post #1
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Old 29th Jan 2024, 11:53 am   #17
SteveCG
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Again, it would be helpful to have confirmation of the source. Is it an actual Philips PAL-M test card generator on the bench or is it possibly a video recording (note the date on the screen)? I only raise it to make sure that in trying to diagnose the issue we know that the source is to be relied upon.
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Old 29th Jan 2024, 12:14 pm   #18
jhalphen
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Hi to all,

From Inaxeon's own web site :

https://www.mattmillman.com/a-quick-...pm5631-pm5644/

the PAL-M generator is the Philips PM5644P/00 (PAL-M) and only this one.
Is the test pattern on the TV screen photo generated by this model? we need confirmation.

The standard PAL model PM5644G/00 (PAL) is useless for PAL-M.

Inaxeon's Github repository with Philips PM generators documentation :
https://github.com/inaxeon/PTV_Preservation

Best Regards
jhalphen
Paris/France
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Old 29th Jan 2024, 12:56 pm   #19
inaxeon
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Default Re: Attempting to modify a UK PAL TV for PAL-M

Quote:
Originally Posted by SteveCG View Post
Again, it would be helpful to have confirmation of the source. Is it an actual Philips PAL-M test card generator on the bench or is it possibly a video recording (note the date on the screen)? I only raise it to make sure that in trying to diagnose the issue we know that the source is to be relied upon.
Valid point. I set the date. The generator is PM5644P/00.
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Old 30th Jan 2024, 11:27 am   #20
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Default Re: Attempting to modify a UK PAL TV for PAL-M

inaxeon, thank you for clarifying the source. At least we know that the issue is on the decode side.
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