PAL red/green color moire, not in NTSC

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rmzalbar
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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar » Sat Feb 01, 2020 10:00 pm

eslapion wrote:
Sat Feb 01, 2020 4:18 pm
You're saying total nonsense here. When you use the VIC-II2, the C64's capacitor and crystal is UNUSED. This board doesn't know what type of C64 board it's going to be installed on so it carries both frequencies since you have both types of 656X. They are clearly marked 'NTSC crystal' and 'PAL Crystal'.

On PAL systems, the dot clock is 4/9 of the color clock and on NTSC systems, the dot clock is 4/7 of the color clock. The VIC-II2 board takes care of the conversion depending on the system/video chip you selected.

The VIC-II2 has it's own 14.31818MHz crystal and it's own 17.7344 MHz crystal. You could completely cut off the crystal that's on the C64 board and everything would still work.
To install the VIC-II2, you remove the original crystal from the motherboard and install a pin header in its place. This gets routed through the PAL or NTSC frequency crystals on the VIC-II2 depending on which mode you have selected. The rest of the timing circuit on the mainboard is still in use, including the discrete 74-series, the 15pf or 16pf tuning capacitor, and the adjustable trimming capacitor. The difficulty is just that you must lift the board to access the trimmer. The VIC-II2 isn't capable of dividing the clock, it doesn't have any components for timing other than these two crystals. It leaves everything to the motherboard's clock circuit.

There is a different version of the PCB for use with 250425, because of different mainboard layout, but it similarly just replaces the crystal itself.
eslapion wrote:
Sat Feb 01, 2020 4:18 pm
You can check for these frequencies on pin 21 of the 656X. Sidenote: You're going to fry the 6567R8 if you don't put an adequate heat sink on it.
I checked that, and I also checked the dot clock frequency on an adjacent pin. I did get it extremely close, certainly within the accuracy of turning a tuning capacitor. I will take another look and get a picture. Oh yes, I have heat sinks bonded to both VIC-IIs with thermal silicone, these can be seen in my first picture. They were just bare for brief testing before I buttoned everything up.
eslapion wrote:
Sat Feb 01, 2020 4:18 pm
That happens to be false. You can tap the chroma directly on the VIC-II. As a matter of fact, it's too strong for S-Video and has to be reduced in intensity with a voltage divider. Two simple resistors can do it.
Ah! Then I may give it a test soon.
eslapion wrote:
Sat Feb 01, 2020 4:18 pm
rmzalbar wrote: I think eslapion has hit it on the head however with a mismatch in phase between dot and color clock. Now to determine what to do next.
I NEVER said anything like that!!

If the color clock is wrong, everything else is derived from it* so everything else will be wrong too. It only needs an error of less than 0.1% for the colors to go wrong. Correctly tuned crystal usually have an error of about 50ppm or less, that's 0.0003%.

* On PAL C64, that's phiColor=17.7344 MHz, phiDot=(4/9) x phiColor=7.882MHz, phi0=(1/8) x phiDot=0.98525MHz
Pardon the misunderstanding. I think it was not initially obvious the VIC-II2 doesn't replace any timing components other than the crystal, and I read that with the idea that you knew this.

I discovered in tuning that the NTSC color was initially sea-green and the PAL color wasn't being detected at all (black and white) due to the new capacitance involved in the crystal switching circuit. Once I put the scope on it and made adjustments, the NTSC color became correct and I got color video in PAL. However, no amount of tuning seemed to reduce these bars. I'll give it another look.



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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar » Sun Feb 02, 2020 12:33 am

Here are pictures from testing as best I could. I am still learning how to use an oscilloscope. This is an old TEK TDS-224.

I do not know if it's possible to increase the digits of the frequency display, which is only giving me two decimals of precision. I set the sample average as high as it would go at 128, because otherwise the trigger point wanders around a little bit because of ripple, which makes the frequency count drift around. I don't know if I'm doing this right, or if there is a better technique I should be using, any thoughts?

The interesting thing is that the single R27 adjuster (actually it's a 500R pot on the 250407 rather than the tunable capacitor that 250425 has) was able to tune both PAL and NTSC mode to this same degree of accuracy. If that were not the case I would have had to add a seperate POT for each mode. I saw in earlier VIC-II2 board revisions that the footprints for this were there, I guess they determined it wasn't needed.

Sample setting, NTSC color clock, PAL color clock.
20200201_150423.jpg
20200201_151537.jpg
20200201_151703.jpg
Last edited by rmzalbar on Sun Feb 02, 2020 12:52 am, edited 6 times in total.

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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar » Sun Feb 02, 2020 12:36 am

Here is where I measure...
20200201_151726.jpg


Here is the board unplugged and flipped upward. You can see the pin headers for the crystal and the pal/ntsc jumper there. I also put the 15pf capacitor C70, that is in series with the crystal, in a pin header so I could experiment with that if I needed to pull the center of the range over. Didn't have to.
20200201_152048.jpg

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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar » Sun Feb 02, 2020 1:37 am

I also ran into a little trouble putting the case back together:


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Re: PAL red/green color moire, not in NTSC

Post by banman » Sun Feb 02, 2020 10:13 am

Hi rmzalbar,

Is that a broken track near C15…?

That must have been really tricky to adjust the trimmer with the C64 off.

Hi eslapion,

That's some very nice soldering work on that PLAnkton PLA chip.
Do you do that or do you get it done at a factory?
Last edited by banman on Sun Feb 02, 2020 10:41 am, edited 1 time in total.

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Re: PAL red/green color moire, not in NTSC

Post by banman » Sun Feb 02, 2020 10:30 am

Hi rmzalbar,

I was just thinking you may want to remove the PAL VIC II chip from the VIC II2 circuit board and plug it straight into the C64 main board and also remove the PAL crystal and put it into the C64 main board.
That way you can get a better live view on a LCD monitor when you fine tune the trimmer.
You may be able to tell if those vertical bars are there due to something on the VIC II2 board or not....

Just a thought....

These things can be frustrating when the solution eludes itself........

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Re: PAL red/green color moire, not in NTSC

Post by eslapion » Mon Feb 03, 2020 4:12 am

rmzalbar wrote:
Sat Feb 01, 2020 10:00 pm
To install the VIC-II2, you remove the original crystal from the motherboard and install a pin header in its place. This gets routed through the PAL or NTSC frequency crystals on the VIC-II2 depending on which mode you have selected. The rest of the timing circuit on the mainboard is still in use, including the discrete 74-series, the 15pf or 16pf tuning capacitor, and the adjustable trimming capacitor. The difficulty is just that you must lift the board to access the trimmer. The VIC-II2 isn't capable of dividing the clock, it doesn't have any components for timing other than these two crystals. It leaves everything to the motherboard's clock circuit.

There is a different version of the PCB for use with 250425, because of different mainboard layout, but it similarly just replaces the crystal itself.
I have to be honest with you; this sounds incredibly stupid for the people who designed this thing. You can't possibly have the same tuning capacitor used for both PAL and NTSC as obviously, the correction needed will be different.

What they are doing is feeding the color clock into the ratio converter of the C64's board. It is then responsible for the 4/7 or 4/9 conversion. They could have put a 525-01R (the chip on TOLB and LumaTOLB) on the VIC-II2 and do completely away with the C64 clock architecture. You have to have a different version for boards 250425 and 250466 since they use the 8701 for the conversion.
I am still learning how to use an oscilloscope. This is an old TEK TDS-224.
I have the TDS-1002 which is a few years younger has an incredibly accurate trigger clock which shows in the bottom right corner. I think it's 6 decimals precision. I thought the TDS-210 and other members of that family had the same feature.
banman wrote:
Sun Feb 02, 2020 10:13 am
Hi eslapion,

That's some very nice soldering work on that PLAnkton PLA chip.
Do you do that or do you get it done at a factory?
That's hand made drag soldering. The CPLD takes only about 30 seconds to solder. If you look at the bottom left corner of the XC9536XL footprint, there is a solder thief to help me.

This video is a tutorial that helped me. You this guy doesn't have a solder thief and he systematically has excess solder on the last few pins.
See:

The CPLD on PLAnkton is quite easy to solder. The sTSOP SRAM chip used on Saruman products is tougher and I do it using a 20x stereoscope.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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Re: PAL red/green color moire, not in NTSC

Post by rmzalbar » Mon Feb 03, 2020 6:44 am

eslapion wrote:
Mon Feb 03, 2020 4:12 am
I have to be honest with you; this sounds incredibly stupid for the people who designed this thing. You can't possibly have the same tuning capacitor used for both PAL and NTSC as obviously, the correction needed will be different.

What they are doing is feeding the color clock into the ratio converter of the C64's board. It is then responsible for the 4/7 or 4/9 conversion. They could have put a 525-01R (the chip on TOLB and LumaTOLB) on the VIC-II2 and do completely away with the C64 clock architecture. You have to have a different version for boards 250425 and 250466 since they use the 8701 for the conversion.
I have the TDS-1002 which is a few years younger has an incredibly accurate trigger clock which shows in the bottom right corner. I think it's 6 decimals precision. I thought the TDS-210 and other members of that family had the same feature.
I just checked, and nope. :( Frequency counter was introduced in 1000/2000 line. Without a true FC, I can't be sure of what I'm doing. Fortunately this is a borrowed scope; I can make sure I shop for one that has an FC in it.

With no further equipment, I should be able to experiment by either converting to PAL without the VIC-II2 board in the way, or by remoting the 500R pot out where I can reach it. A live adjustment should confirm if timing is correlative to the color bars. Most quickies on converting to PAL just say "Hey malchik, just twist the thing back and forth until you get color!"
That's hand made drag soldering. The CPLD takes only about 30 seconds to solder. If you look at the bottom left corner of the XC9536XL footprint, there is a solder thief to help me.

This video is a tutorial that helped me. You this guy doesn't have a solder thief and he systematically has excess solder on the last few pins.
Thanks for that video. I've done a few drag solders, but there's always something to be learned by watching someone else. Solder thief is a new concept for me.

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Re: PAL red/green color moire, not in NTSC

Post by banman » Tue Feb 04, 2020 5:13 am

Hi eslapion,

eslapion wrote:
Mon Feb 03, 2020 4:12 am
That's hand made drag soldering. The CPLD takes only about 30 seconds to solder. If you look at the bottom left corner of the XC9536XL footprint, there is a solder thief to help me.

This video is a tutorial that helped me.
I like like your work very much.... :D

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Re: PAL red/green color moire, not in NTSC

Post by eslapion » Wed Feb 05, 2020 12:46 am

rmzalbar wrote:
Mon Feb 03, 2020 6:44 am
Solder thief is a new concept for me.
It's very difficult to control the exact amount of solder required for soldering a series of pins, especially on very small ICs with not so many pins, such as a TSSOP-14.

Having a little square area with bare HASL immediately after the pins is helpful as you can simply slide the iron past the last pin and get it to suck up whatever extra solder you put on the iron's tip.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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