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Intellivision Model 3668 PAL60 Mod


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#1 HunterZero OFFLINE  

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Posted Tue Oct 11, 2016 7:13 PM

It might have been missed since it's buried in another thread (http://atariage.com/...c-needed/page-2), but just wanted to share this awesome MOD and document it in its own thread.

 

Parts used for this mod: AY-3-8900-1 NTSC STIC, 3.5795MHz crystal

 

A bit of background - The PAL territory Intellivisions run many games at different speeds to the USA version of the console. The PAL CPU runs faster, but the video refresh is slower. Since the games are synched to the video refresh, the gameplay is slower. The pitch and speed of the sound is different too thanks to the different speed the CPU runs at.

 

Most notable is D2K - the game and music runs around 12% slower, and the sound pitch is higher. Dreadnought Factor won't run at all on a PAL system.

 

I picked up a model 3668 PAL Australian Intellivision that turned out to have a bad AY-3-8900 CCIR PAL STIC. I had no spares of this chip, but had an AY-3-8900-1 NTSC version of the chip lying around. Since the two are pin compatible, I speculated if it was possible to swap the NTSC chip in and mod the system to run at USA clock rates, and to produce a PAL60 RF signal - 60Hz refresh with PAL encoded colours.

 

Earlier 3668 model Intys seem to have a daughter board that produces the colour information, this Intellivision motherboard revision does not have this daughter board and instead has an onboard colour chip. It shouldn't matter which version your system is.

 

I swapped just the STIC out and tried the system - it worked, but the video was out of synch.

 

The PAL Intellivision has two crystals onboard - one at 4.4MHz for the PAL colour generation, and a 4.00MHz system clock (nearest the CPU). I swapped the 4.00MHz crystal for a 3.5795MHz crystal and tried it again - it worked!

 

post-34908-0-97157300-1476164380.jpg post-34908-0-62982600-1476164424.jpg

 

The system runs at the correct clock rates, with correct USA game speeds and sound pitch, on a PAL 60 TV. The picture quality is excellent. As an added benefit the picture fills up more of the screen.

 

I am astounded at how simple the mod was, I was fully expecting to have to make further mods to the RF video circuit, but the RF circuit is unchanged. Since the mod is so simple it should be compatible with other mods, eg composite mod.

 

A big THANK YOU to intvnut for his technical assistance with this mod!

 

It should be noted that I am using the modified console with a later Sony CRT that supports 60Hz refresh rate, obviously earlier 50Hz PAL CRT TVs won't be able to synch with the modified video signal.

 

- James


Edited by HunterZero, Tue Oct 11, 2016 7:18 PM.


#2 Utopia OFFLINE  

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Posted Thu Oct 13, 2016 1:03 AM

I was getting all excited about this possible mod until I checked both CRT sets I have..............both are 50hz, bummer :(

Will I ever get to play The Dreadnought Factor??



#3 HunterZero OFFLINE  

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Posted Thu Oct 13, 2016 9:38 AM

I was getting all excited about this possible mod until I checked both CRT sets I have..............both are 50hz, bummer :(
Will I ever get to play The Dreadnought Factor??


That might be the input AC requirement, 240V 50Hz?

What models are they? Check to see if the TV supports NTSC as well as PAL. If it does, it will probably do 60Hz refresh rates.

#4 intvsteve OFFLINE  

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Posted Fri Oct 14, 2016 5:25 PM

I was getting all excited about this possible mod until I checked both CRT sets I have..............both are 50hz, bummer :(

Will I ever get to play The Dreadnought Factor??

If you've got an Intellicart!, CuttleCart3, or LTO Flash! you can! There's a patch to the .cfg file that makes it work for PAL systems. Load it up and it should work!



#5 HunterZero OFFLINE  

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Posted Thu Oct 20, 2016 6:34 PM

Here's a pic of XTAL2 replaced by this mod...

20161020_232310.jpg

#6 intvnut OFFLINE  

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Posted Wed Oct 26, 2016 8:20 PM

The grid-covered crafting/project mat you have underneath it adds a nice touch to the photo.   :D


Edited by intvnut, Wed Oct 26, 2016 8:20 PM.


#7 archimage OFFLINE  

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Posted Mon Jul 10, 2017 4:43 PM

Hello ! Do you know if this mod works with SECAM Intelliivisions ?



#8 CatPix OFFLINE  

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Posted Mon Jul 10, 2017 5:09 PM

I was getting all excited about this possible mod until I checked both CRT sets I have..............both are 50hz, bummer :(

Will I ever get to play The Dreadnought Factor??

Most PAL TV sets made after 1990 support 60 htz.

The older TV set I have that support 60 htz is a 1983 one.

Older one might support 60 htz if you have manual vertical hold tuning and that it have a sufficient range - some sets have, other doesn't.



#9 HunterZero OFFLINE  

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Posted Mon Jul 10, 2017 7:57 PM

Hello ! Do you know if this mod works with SECAM Intelliivisions ?

 

No, I don't think that this will work.

 

PAL is an amplitude modulated signal, SECAM is frequency modulated. As far as I know, there is only a 50Hz standard for SECAM, whereas PAL has 50Hz and 60Hz variants.

 

- J



#10 archimage OFFLINE  

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Posted Sat Jul 15, 2017 1:22 PM

My Intelllivision has been modded to RGB from Secam, so I guess the signal is not Secam anymore, does it change anything ?



#11 HunterZero OFFLINE  

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Posted Sun Jul 16, 2017 7:25 PM

My Intelllivision has been modded to RGB from Secam, so I guess the signal is not Secam anymore, does it change anything ?

 

Yes that could change things, since you'd be splicing into the video signal before the RF encoding - Have you removed the SECAM daughter card completely? Where are you getting the video colour/luminance from? What colour system chip does the SECAM board use? Do you have a pic of your modded board?

 

The mod is so simple you may as well try it (if you have the parts) - Swap the 4.00MHz XTAL for 3.579545MHz one to get the correct clock rates, and swap the AY-3-8910 CCIR STIC for an AY-3-8900-1 NTSC STIC.


Edited by HunterZero, Sun Jul 16, 2017 8:06 PM.


#12 archimage OFFLINE  

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Posted Sun Jul 16, 2017 9:09 PM

I didn't make the mod myself actually, I bought it already done. The daughterboard is completely removed yes.

 

I think it's worth trying.

 

Do you know where I can buy AY-3-8900-1 chips ?

 

I want to avoid wasting an NTSC intellivision (plus shipping fees) to get one



#13 HunterZero OFFLINE  

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Posted Sun Jul 16, 2017 10:59 PM

Do you know where I can buy AY-3-8900-1 chips ?

 

I want to avoid wasting an NTSC intellivision (plus shipping fees) to get one

 

Use the search function, there is another thread on here where a member had some new-old stock parts to sell, including STIC chips.






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