Atari 800 NTSC to PAL conversion

[+Philsan]

Is it possible to convert a NTSC 800 to a PAL 800?

I think those parts need to be changed with PAL ones:

CPU PCB

ROM PCB

Power PCB

 

Main motherboard

needs to be changed with a PAL version too?

 

I don't think RAM cards or keyboard have to be changed.

 

Other parts?

 

 

 

[Rybags]

Depends how "PALified" you want it to be.

 

A minimal approach is to just put the PAL Antic in but you still end up with NTSC colour encoding, plus the master clock difference means the scanline frequency will be slightly higher than it should be. Plus GTIA contains the PAL register which means software will usually interpret it as being an NTSC machine.

 

GTIA as well - PAL GTIA has the seperate clock input for the PAL colour signal where NTSC machines can just derive it from the master clock.

 

I'm not sure how a PAL GTIA will behave without that input, you'd probably get a monochrome only picture.

 

Feeding the master clock from NTSC into that pin should in theory give a PAL signal but at NTSC frequency (3.59 instead of 4.3 MHz).

 

RAM modules and keyboard - no difference.

OS module - the 400/800 have hard-coded OSes that are region specific where the XL is universal and doesn't need changing.

You'd get away with retaining the existing OS but cassette operations might become unreliable. The key repeat would become annoyingly slow for a NTSC to PAL conversion.

 

I imagine the 400/800 would be hardest of all the Ataris to convert from one standard to the other due to multiple boards and the video generation being spread among them.

 

AFAIK, most people who do standard changes on their own gear just settle with changing the Antic and NTSC, then persist with the colour signal being from the other standard.

Some TVs will handle it, some will just give black&white, some will have a rolling picture.

[+Philsan]

Thanks Gary.

 

I mean a perfect, complete, "PALification".

 

I don't know if PAL and NTSC main motherboards are the same or not.

[thorfdbg]

Thanks Gary.

 

I mean a perfect, complete, "PALification".

 

I don't know if PAL and NTSC main motherboards are the same or not.

Neither do I, but the major problem here is that the color carrier of PAL is different from the base pixel frequency (unlike NTSC). For that, the PAL GTIA requires in addition to the Phi_2 clock source the color carrier base frequency at 5/4th of Phi2. In the PAL Ataris, a separate circuit first divides Phi_2 by four by two 74LS74 D-Flip Flops and feed this into a crystal running at 5/4 the base clock. Whether there is enough room on a NTSC board to place and wire these components I don't know, probably not.

 

This, plus replacement of the main crystal, the GITA and the ANTIC by their PAL counterparts, would give you a PAL compliant FBAS signal on the monitor output. If you want TV (antenna) input, you would also need to replace the HF modulator by a PAL conforming one, of course.

 

So long,

Thomas

[Rybags]

I didn't realise that the colour crystal on PAL worked in that way, actually never really gave it much thought.

 

But of course it has to since it needs to be resynced on each colour-clock boundary.

 

The other consideration with RF is that the modulators are not only region specific but there's variation among countries, ie what channel is used (not really a big problem), and the seperation between video and audio frequency (which is a problem since you need the correct seperation for your TV to be able to tune into both of them).

 

Really I think the easiest option would probably be to just swap with someone who wants an NTSC machine.

[+tf_hh]

Hi,

Is it possible to convert a NTSC 800 to a PAL 800?

It´s possible, I´ve done that for a friend a few years ago. You have to change:

 

- system crystal (from 3.579 MHz to 3.546 MHz (Atari part no. CO16112 ))

- ANTIC (Atari part no. CO21698 (the XL/XE type with more 8-Bit refresh, better for DRAM based memory expansions) or the older one from 800 with 7-Bit refresh: CO14887)

- GTIA (Atari part no. CO14889 - I´m not really sure, but I never heard about a second PAL version of the GTIA or a PAL version of the CTIA).

- Operating system ROMs (better to rip-off the three ROMs, insert one 27128 and a logic TTL).

 

The OSC input on pin 28 of the GTIA is coupled to pin 16 of the GTIA. The connection to pin 16 (from pin 28) must be cut-off. On pin 16 ("PAL") you must make a connection to a little circuit for generating the PAL color offset clock. These little circuit is shown in the picture attached. The crystal in this circuit is the PAL standard clock = 4.33618 MHz (Atari part no. CO16801, but can be ordered at ANY electronics store in europe).

 

And finally: The HF modulator won´t work. If you want to connect the 800 to a television, also a new modulator is necessary. Better rip-off that sh*t and use a FBAS monitor

 

Regards, Juergen

 

[+Philsan]

Thank you Jürgen, but I am an hardware n00b.

Best Electronics sells PAL CPU PCBs and PAL ROM PCBs.

Should NTSC Power PCB be changed with a PAL one?

And what should be changed in main motherboard?

Where is the modulator? In Power PCB?

Here are two photos from ABBUC:

[sup8pdct]

There is one other part that that also needs to be changed on the motherboard. From memory (which is very hazy) an inductor around the video/audio circuit which ultimately goes to the modulator also needs to be changed.

 

I will need to look through old notes to find it.

James

 

 

 

 

Hi,

Is it possible to convert a NTSC 800 to a PAL 800?

It´s possible, I´ve done that for a friend a few years ago. You have to change:

 

- system crystal (from 3.579 MHz to 3.546 MHz (Atari part no. CO16112 ))

- ANTIC (Atari part no. CO21698 (the XL/XE type with more 8-Bit refresh, better for DRAM based memory expansions) or the older one from 800 with 7-Bit refresh: CO14887)

- GTIA (Atari part no. CO14889 - I´m not really sure, but I never heard about a second PAL version of the GTIA or a PAL version of the CTIA).

- Operating system ROMs (better to rip-off the three ROMs, insert one 27128 and a logic TTL).

 

The OSC input on pin 28 of the GTIA is coupled to pin 16 of the GTIA. The connection to pin 16 (from pin 28) must be cut-off. On pin 16 ("PAL") you must make a connection to a little circuit for generating the PAL color offset clock. These little circuit is shown in the picture attached. The crystal in this circuit is the PAL standard clock = 4.33618 MHz (Atari part no. CO16801, but can be ordered at ANY electronics store in europe).

 

And finally: The HF modulator won´t work. If you want to connect the 800 to a television, also a new modulator is necessary. Better rip-off that sh*t and use a FBAS monitor

 

Regards, Juergen

 

[Havok69]

It would probably just be easier to get a monitor that can handle NTSC as well as PAL...

[Magic Knight]

Im thinking of doing this with a NTSC 800 for the uk (PAL-I)

 

To recap the above - to change a NTSC to PAL-I - i understand i would change...

 

- system crystal (from 3.579 MHz to 3.546 MHz (Atari part no. CO16112 ))

- ANTIC (Atari part no. CO21698 (the XL/XE type with more 8-Bit refresh, better for DRAM based memory expansions) or the older one from 800 with 7-Bit refresh: CO14887)

- GTIA (Atari part no. CO14889 - I´m not really sure, but I never heard about a second PAL version of the GTIA or a PAL version of the CTIA).

- Operating system ROMs (better to rip-off the three ROMs, insert one 27128 and a logic TTL).

- Play around with pin 16 and 28 of the GTIAand affect the little circuit shown in the diagram.

- change the modulator to a PAL one

 

To make things simpler would i get away with it if? >

 

- i substituted the required boards and modulator from a UK PAL A400

- affect the GTIA (as explained earlier)

- use a UK power supply (220-240Vac)

 

would this be all i would have to do to get this running on a 50hz television?

 

Onacheaper note - would putting a £20 ntsc to pal convertor box-thing on composite do the trick instead? -through the 5 pin monitor port of course ( with a uk PSU and use a 60hz capable tv).

 

a few questions i know but it would be great if this was as simple as it may look and with the above options.

[+Stephen]

The only thing I can answer for you, is the question about a convertor box. I use a scan doubler (Y/C or composite to VGA). It works with NTSC and PAL which is an advantage. It eliminates flicker on the interlaced modes, which is another advantage. However, it cuts the framerate in half, scrolling is never smooth like it should be, and there are issues with the fact that every other field on the Atari is not shifted by a single scanline like it should be.

[mimo]

If you have a 60hz tv, you could probably get away with just pal antic.

Forget the ntsc to pal converter, they are horrible. You can have mine for the cost of post if you really want to go down that route.

[Magic Knight]

Thanks guys

 

I may try swopping the boards change crystal and the link on the GTIA. Being as its a signal type frequency and not messing with power as such, i dont think much risk is run as ive played around with similar before (trying to record from ntsc video to my video card - and getting b/w)

 

Especially dont want to spend the £120 or so for a pukka resampler to take it to from 60hz to 50hz as its a cost id rather spend elsewhere.

 

i think its maybe also that a pal vhs recorder may take the ntsc signal and translate to the (50hz) tv - this may work as it works on video tapes and some dvd through types in the past.

[Beeblebrox]

I plan on doing this PAL mod for my NTSC 800. (Bought it on the understanding it was a PAL system and when it arrived it was NTSC with and NTSC personality board, the crystal on the main board, etc).

 

I have also already undertaken the Incognito upgrade preparation, (already installed in advance of the Incognito board itself arriving next week). I've installed quite a few Incognitos so very comfortable with that side. See my blog link to the Incognito install guide I created in my signature).

 

So reading above posts in this thread, in addition to the new PAL personality board with the PAL ICs in place, I read that there is the tweaking of the connection with the GTIA and tapping into a circuit needed. Plus the large NTSC 3.579575mhz crystal top left of the mainboard needs replacing with a PAL NON-Colourburst 3.546mhz crystal, (presumably from another PAL XL/XE), part no. CO16112

 

First question:

 

I understand I can buy a modern crystal CO16112 equivilent rather than salvaging one from an A8. I've tried searching online for a supplier in the UK, (since the Brewing academy sells them but the shipping would be a killer to the UK), but had no luck. Anyone know the link for one? I believe I could salvage one from an Atari 2600 but tbh would rather just source the crystal new.

 

2nd question:

 

According to SAMS computer facts for the 800, (See here for the NTSC related one), the crystal to replace is the large X101 (C010177-01):

 

 

..here it is on my board next to that large green cap:

  

 

The orientation for the new crystal on the board presumably is the same way, with the PAL crystal's markings facing into the board? (I am guessing connecting it up the wrong way would damage the crystal?)

 

Question 3: 

 

I understand given the OS rom is removed and replaced by the Incognito's onboard OS that this is covered. As such I therefore take it that nothing related to the OS swapping you would normally do is required once the Incognito is hooked up in this setup?

 

Question 4: 

 

I must admit I am not great at interpreting schematics so looking at Jurgen's one above for the circuit connections for the PAL colour offset clock I am assuming no new components or ICs are being added here, just new connections on the existing board to existing components/ICs needed? This probably is the one area of the whole conversion I am unsure of. If anyone has undertaken this and has a series of photos of this particular part great. 

 

@Philsan did you ever go through with the conversion yourself 10 odd years ago? Any pictures or advice? If so thanks in advance. 

 

Question 5

 

I am not bothered about using the RF modulator so will just leave the current one in place. I assume this won't be an issue? 

 

Question 6

 

The following is mentioned above which I am unsure about:

 

"inductor around the video/audio circuit which ultimately goes to the modulator also needs to be changed." 

 

Is this required and if so any specifics? 

 

Anything else anyone has to add would be greatly apperciated. 

 

At present before I added the required infrastructure in advance of the Incognito card arriving the 800 powers up on UK mains with the new PAL personality cart with no problem save the black and white image - which is to be expected with no colourburst. FYI I am hooked up to my LCD and CRT via DIN to S-video - my default connection for all my A8s.

 

 

Thanks in advance for any advice. 

 

BTW I plan to either pop some heatshrink on some of the ends of the Incognito wiring that connects to some vias on the mainboard. (to stop any pontial shorting). I just didn't have them to hand yesterday evening.

 

Edited September 25, 2022 by Beeblebrox

[+Philsan]

> @Philsan did you ever go through with the conversion yourself 10 odd years ago? Any pictures or advice? If so thanks in advance. 

 

Unfortunately it was too much complicated for my skills...

 

[Beeblebrox]

thanks Philsan

 

Interestingly I've just found the following post from Andymanone which fills me with hope that - if I fail to get to grips with some aspects of this conversion relating to the colpour burst circuit - at least I can grab a SCCC from Tf_hh, (if still available):

 

https://forums.atariage.com/topic/336918-incognito-in-an-ntsc-atari-800-what-does-pal-option-do/?do=findComment&comment=5074140

 

"I used TF_HH's Super Color CPU Card (SCCC), and then replaced GTIA (CO14805) and ANTIC (CO12296) with PAL versions (CO14889 and CO12698), and changed the system crystal on the mainboard.

 

That works perfectly."

 

Still would love to be able to answer the questions I posed earlier and at least try before I go down that route.

[Beeblebrox]

Just an update. I've just completed the NTSC to PAL conversion of my Incognito'd NTSC Atari 800.

 

Turns out the NTSC to PAL conversion was pretty simple, even more so if you have Incognito installed.

 

(Thanks to @Lambda Mikel for PM chat help in late Sept BTW - very helpful) Thanks also to anyone who commented and helped above.

 

A new PAL personality/CPU board with PAL versions of GTIA, ANTIC and the CPU chips in place, and a replacement crystal, (taken from a dead Atari 2600), with the Incognito replacing the OS rom board it - saw it working perfectly. 

 

The little CO16112 crystal looks quite out of place having replaced it's larger footprint ol school NTSC flavour 800 crystal! It's little mounting pins really have to be bent out to reach the solder pads. Does the trick though. 

 

Currently the 800 is out of it's case for easy testing purposes and as I don't have a spare CF card to use in it I've used my SIDE3 cart (with FJC's beta firmware), in the left cart slot and also SIO2PC USB with RespeQt so all good. A few pics below.

 

(And yeah - no keycaps on the stackpole keyboard and I will be tiding up those wires once I get it back in the case  )

 

 

   

 

  

 

Games loaded from SIDE3 cart:

      

 

Rewind demo looks great, (again running off the SIDE3 cart):

                    

Edited October 15, 2022 by Beeblebrox

[santosp]

Question!

Have anyone find the schematic diagram of PAL CPU board for Atari 800 anywhere? In every service manual that have in my possession, only the NTSC CPU board is available.