PAL 3.546895MHz Crystal Alternative Solutions

[Overange]

As it's becoming increasingly challenging to find PAL 3.546895MHz and 14.187576MHz PAL Crystals for those interested in constructing modern clones, remakes, conversions or even repairs, I've been exploring potential alternatives to achieve the desired 3.546895MHz frequency.

 

I'm interested in finding the most cost-effective and straightforward solution. While there are programmable options available, I believe I've identified a straightforward approach that involves the Amiga.

In PAL variants of the Amiga, a 28.37516MHz Crystal Oscillator is used and is still available.

My proposal involves dividing this frequency by 8 to attain the required 3.546895MHz OSC Clock signal for PAL with in the A8 Systems.

 

I've been examining the use of the 74HC4040 for this division task, has anyone else explored this approach of clock signal division?

 

Regarding the Freddie/XE variants, the PAL 14.187576MHz clock signal is divided by 4 to give 3.546895MHz. I think the easiest option would be to bypass the Freddie and connect the new OSC clock signal directly to the GTIA?

 

If this proof of concept proves successful, it could offer a straightforward solution to address the issue of PAL crystal scarcity.

 

 

[Beeblebrox]

Cool.

 

There is a pre existing pcb solution for the stock 800xl and 600xl A8's called a quartz generator available from Poland which provides a replacement pal system clock crystal and a few other video circuit component replacements. 

 

QARTZ ATARI CO12285 (C012285) - quartz generator for ATARI 600XL 800XL

https://www.ebay.pl/itm/125907145257

 

 

 

 

 

 

 

 

 

That still leaves the pal colourburst crystal. Whenever I need one when converting ntsc A8's to PAL I have to source a broken Atari 2600 to salvage the colour burst crystal. Can be a little expensive. 

Edited September 14, 2023 by Beeblebrox

[Overange]

Thats why I could not find it lol....

 

I see what he is doing, he is dividing the the 14.187576MHz crystal signal by 4, basically what the Freddie does internally, he then puts the new PAL OSC signal back into U21s Pin 3, and the rest of his circuit performs the task of the old removed 74hct74 device with in the Colour Burst Circuit.

 

But.... the 14.187576MHz Crystals are now also getting harder to find??

 

 

[+scorpio_ny]

Maybe this is helpful. Since I built the XE remake, I recall that ABBUC website has a BOM for the PAL version.. In their collective contribution post there is a BOM file. In that file they recommended these parts:

 

3,57945MHz

14.18757MHz

 

They are available too.

 

The post was from a while ago, and even then they said the same thing that it was hard to get these components.

 

 

 

 

 

 

 

 

Edited September 14, 2023 by scorpio_ny

[Peri Noid]

Don't forget, that if you have VBXE installed, you can use it as a source of a clock. It's available at one of its pins and easy to use. Then an oscillator is completly redundant... and can be used to restore a board, which needs it.

[Piotr D. Kaczorowski]

But why? I bought a lot of these quartz. They are generally available. You just need to check some online shops....

[+bent_pin]

These align with many ham radio bands. Suitable replacements should be cheap and plentiful.

[Piotr D. Kaczorowski]

8 minutes ago, bent_pin said:

These align with many ham radio bands. Suitable replacements should be cheap and plentiful.

 

 

0.70 PLN = 0.16 USD .....   Are you looking for a better price?

 

 

[+bent_pin]

3 minutes ago, Piotr D. Kaczorowski said:

0.70 PLN = 0.16 USD .....   Are you looking for a better price?

 

Fantastic price, if'n you ask me.

[Beeblebrox]

30 minutes ago, scorpio_ny said:

Maybe this is helpful. Since I built the XE remake, I recall that ABBUC website has a BOM for the PAL version.. In their collective contribution post there is a BOM file. In that file they recommended these parts:

 

3,57945MHz

14.18757MHz

 

They are available too.

 

The post was from a while ago, and even then they said the same thing that it was hard to get these components.

 

 

 

 

 

 

 

 

Cool.

 

Is there an equivalent seller other than alibaba for the modern colourburst pal equivalent? 

 

So the one on alibaba can be used on a stock A8 (say 800xl) as a direct replacement for the original pal colourburst? 

 

 

 

 

[+scorpio_ny]

2 hours ago, Beeblebrox said:

Cool.

 

Is there an equivalent seller other than alibaba for the modern colourburst pal equivalent? 

 

So the one on alibaba can be used on a stock A8 (say 800xl) as a direct replacement for the original pal colourburst? 

 

 

 

 

Out of curiosity @Beeblebrox, what do you have in your PAL Atari XL’s? Are they crystals or metal 4 pin oscillators?

[Beeblebrox]

3 hours ago, scorpio_ny said:

Out of curiosity @Beeblebrox, what do you have in your PAL Atari XL’s? Are they crystals or metal 4 pin oscillators?

PAL XL's (stock 800XL and 600XL), only come with crystals, whereas XEs come with a mixture of crystal and oscillators. I've never seen a PAL 800XL (stock) or 600XL with an oscillator before.

 

Stock 130XE (PAL):

 

Stock 800XL (PAL) Rev D PCB:

 

 

Stock 600XL (PAL):

 

 

Interestingly the Freddie equipt 800XLF PAL usually comes with 2 x crystals, but there is space on the board bottom left near Freddie for an oscillator in place of a crystal. This makes sense as the XLF is essentially an XE anyways.

 

I've worked on a good few XLFs and I've never seen one populated with an oscillator, just two crystals.

 

Stock 800XLF (PAL):

Edited September 15, 2023 by Beeblebrox

[Overange]

1 hour ago, Beeblebrox said:

 

 

I've worked on a good few XLFs and I've never seen one populated with an oscillator, just two crystals.

 

Stock 800XLF (PAL):

 

The option for the oscillator is there..

 

[Beeblebrox]

21 minutes ago, Overange said:

 

The option for the oscillator is there..

 

 

1 hour ago, Beeblebrox said:

Interestingly the Freddie equipt 800XLF PAL usually comes with 2 x crystals, but there is space on the board bottom left near Freddie for an oscillator in place of a crystal. This makes sense as the XLF is essentially an XE anyways.

indeed

[+scorpio_ny]

That is interesting! Why does the PAL Ataris require two clocks?

[Overange]

8 hours ago, Piotr D. Kaczorowski said:

 

 

0.70 PLN = 0.16 USD .....   Are you looking for a better price?

 

 

Thats an NTSC Clock Crystal for an XL Based System

 

 

 

9 hours ago, scorpio_ny said:

Maybe this is helpful. Since I built the XE remake, I recall that ABBUC website has a BOM for the PAL version.. In their collective contribution post there is a BOM file. In that file they recommended these parts:

 

3,57945MHz

14.18757MHz

 

They are available too.

 

The post was from a while ago, and even then they said the same thing that it was hard to get these components.

The top is an XL NTSC Clock Crystal.

The bottom is XE/Freddie Pal Variant

 

 

It does get confusing

 

Just to clarify the crystal types and their availability, using Mouser as a part number source....

 

 

XL Based Systems
PAL = 3.546894MHz - Obsolete
NTSC = 3.579545MHz - Still Produced - Mouser Part No 710-830003056B 

 

Freddie/XE Systems
PAL = 14.187576MHz - Obsolete - may find old Chinese stock
NTSC = 14.31818MHz - Still Produced - Mouser Part No 815-AB-14.31818B2

 

PAL Colour Boost = 4.433618MHz - Still Produced - Mouser Part No 520-HCA443-20X

 

 

[Beeblebrox]

5 minutes ago, scorpio_ny said:

That is interesting! Why does the PAL Ataris require two clocks?

One is the system clock and the other a PAL colourburst crystal

 

https://www.csse.canterbury.ac.nz/greg.ewing/c64_pal_decoder/PAL/PAL-Video-Encoding.html

[Overange]

5 minutes ago, scorpio_ny said:

That is interesting! Why does the PAL Ataris require two clocks?

In a nut shell 🤪

 

Colour Encoding and PAL Standard: The Atari systems was designed to work with the PAL (Phase Alternating Line) video standard, which is the television standard used in many European countries and some other regions. PAL video signals operate at a different frequency than the NTSC (National Television System Committee) standard used in North America and Japan.

 

50 Hz vs. 60 Hz: The PAL standard operates at 50 Hz, whereas the NTSC standard operates at 60 Hz. This difference in frequency affects the generation of colour in the video signal. To generate colour in an NTSC signal, you typically use a colour burst signal at a specific frequency (3.579545 MHz ). However, this frequency doesn't work well with the 50 Hz PAL standard.

 

Chroma Frequency: In PAL systems, the colour encoding relies on the phase difference between the colour subcarrier frequency (chroma) and the line frequency. The PAL colour subcarrier frequency is 4.43361875 MHz ( PAL Colour Burst Crystal Value). To achieve the necessary phase relationship between the colour subcarrier and the 50 Hz PAL signal, the Atari systems used two crystals:

• One crystal oscillated at 3.546894MHz in XL based system and 14.187576MHz in the XE/Freddies based systems ( the Freddie divided this signal by 4 to give an output of 3.546894MHz ) : This crystal was used as the master clock OSC and was also responsible for generating the colour subcarrier frequency (4.43361875 MHz) when divided down.
• Another crystal oscillated at 4.43361875 MHz: This crystal was synchronized with the colour subcarrier frequency and used to generate the chrominance signal, which encodes the colour information for the PAL signal.

By using these two crystals in conjunction, the Atari systems could generate a PAL-compatible video signal with the correct colour encoding and phase relationships.

 

In summary, the use of two crystals in the PAL Atari (Atari systems) was necessary to generate a video signal that complied with the PAL standard's specific requirements, including the chrominance frequency needed for proper colour encoding in a 50 Hz environment.

[Piotr D. Kaczorowski]

1. I bought crystals for PAL and NTSC without any problem.
2. Galtron, who is a manufacturer of boards on Ebay, wrote on our Atari forums that he made them. Duddie - the manufacturer of PokeyMax replied that he ordered the crystal grid directly from the manufacturer and also has no problem making them to order.
3. I replace the 14Mhz crystals with VBXE and that's the best solution
4. Nevertheless, if someone has an availability issue, the ones on Ebay will probably work.

[+scorpio_ny]

Good stuff! Thanks @Overange and @Beeblebrox!

 

By the way, there are two sources that have them in stock: The Brewing Academy and Best Electronics. 

[Overange]

1 hour ago, Piotr D. Kaczorowski said:

1. I bought crystals for PAL and NTSC without any problem.
2. Galtron, who is a manufacturer of boards on Ebay, wrote on our Atari forums that he made them. Duddie - the manufacturer of PokeyMax replied that he ordered the crystal grid directly from the manufacturer and also has no problem making them to order.
3. I replace the 14Mhz crystals with VBXE and that's the best solution
4. Nevertheless, if someone has an availability issue, the ones on Ebay will probably work.

 

Are you talking about the 3.546894MHz or 14.187576MHz ?

 

Either way this is cool as for anyone trying to search for ones in the future, this topic will hopefully help find a solution:-

 

Along with your list above:-

 

XL Based 3.546894MHz PAL options are:-

 

Salvage from a PAL 2600 JNR

From eBay - QARTZ ATARI CO12285 (C012285) - quartz generator to ATARI 600XL 800XL

Upgrade to VBXE

 

XE/Freddie based systems 14.187576MHz PAL options are

 

Upgrade to VBXE

Chinese sites

Polish Electronic Suppliers

48 minutes ago, scorpio_ny said:

By the way, there are two sources that have them in stock: The Brewing Academy and Best Electronics. 

For us in Europe is the cost of shipping etc, but that's cool to know.

 

Edited September 15, 2023 by Overange

[Beeblebrox]

8 hours ago, Overange said:

QARTZ ATARI CO12285 (C012285) - quartz generator to ATARI 600XL 800XL

Upgrade to VBXE

I wonder if this can be used in the 1200xl, if in addition you swap out the ntsc antic and gtia chip with pal versions, and add the pal system clock crystal, (or VBXE)? 

[Overange]

11 minutes ago, Beeblebrox said:

I wonder if this can be used in the 1200xl, if in addition you swap out the ntsc antic and gtia chip with pal versions, and add the pal system clock crystal, (or VBXE)? 

You will still need the PAL colour burst circuit.

 

@mytek PalBurst Board that fits under the PAL GTIA should help with this.

 

 

It would technically cheaper, but VBXE could be better in the long run.

 

[Beeblebrox]

@Overange thanks. So basically the QARTZ ATARI CO12285 (C012285) - quartz generator is a no no for the 1200xl? 

[Overange]

3 minutes ago, Beeblebrox said:

@Overange thanks. So basically the QARTZ ATARI CO12285 (C012285) - quartz generator is a no no for the 1200xl? 

Thats is correct, forget to mention that bit as that IC it replaces is not on the 1200XL board.

 

However.......

 

With the information acquired above it could be possible to redesign @mytek PalBurst Board to integrate the 14.187576MHz Crystal and a /4 Circuit to achieve the 3.546895MHz OSC Signal, therefore a one trick kit conversion from NTSC to PAL?