How to switch PAL Rev 6A A500 between PAL/NTSC?

BarryB · 01 August 2016, 22:33

Seeing as I have a Rev 6A PAL A500 with a Fat Agnus (8372A), how to switch between PAL/NTSC? Is it as simple as just soldering a switch on JP4? If so, I see a problem with this as one of the pads has almost been obliterated as there is a round hole been made between both pads to cut the connection but has taken off most of the pad near the Agnus chip making soldering extremely unlikely! So, is there any other way to do this, other than the pin 41 mod on the Agnus chip as I'd rather not go that route if possible, plus I've not seen how that mod is done!!

I also have an Indi ECS fitted going via VGA to an LCD monitor so 60hz shouldn't be an issue.

dirkies · 01 August 2016, 23:29

U also need to replace the oscillator afaik

BarryB · 01 August 2016, 23:36

Not seen that mentioned for PAL/NTSC switching, for converting permanently a PAL or NTSC Amiga from one to the other then yes, i'd agree the crystal needs changing as well!

dirkies · 01 August 2016, 23:38

But what's the point of keeping it ntsc? Oscillator affects timing for demos aswell i read.

BarryB · 02 August 2016, 02:20

But I don't want it NTSC permanently, I want to switch between PAL and NTSC! From what I read the 1mb/2mb Agnus allows this?

idrougge · 02 August 2016, 02:33

No oscillator needed unless you're running a genlock or something.

ReadOnlyCat · 02 August 2016, 02:47

The oscillator is needed for code which requires cycle precise synchronization.

If you want to be able to switch between PAL and NTSC including oscillators you will need to make a small board with switching logic and plug both oscillators on it. Assuming your motherboard supports dual NTSC/PAL Agnus models you won't need to switch that one but if it doesn't then you would have to switch these too which frankly would be a pain.

TjLaZer · 02 August 2016, 06:47

Don't even bother with a hardware method, just use tools like Degrader, Embedder, PAL/NTSC or BootNTSC/PAL. All on Aminet.

mark_k · 02 August 2016, 15:00

Quote:

Originally Posted by ReadOnlyCat

The oscillator is needed for code which requires cycle precise synchronization.

I don't think that's true.

BarryB · 02 August 2016, 20:08

You know, I think i'll just plug my ACA500 back in and do it that way!!

Zetr0 · 03 August 2016, 14:41

In regards to the oscillator this only impacts the NTSC colour encoding while the custom chips run about 20% faster as it keeps timing with the video of 60Hz.

European Amiga's have a 50Hz PAL output when you put this in NTSC mode, it is in fact still PAL colour encoding but at 60Hz - interestingly most modern TV's support PAL60, however you do lose a few scan lines at the bottom.

I suspect that if you have a NTSC market Amiga then you would be stuck with either 60Hz NTSC or 50Hz NTSC - I don't know how an NTSC TV would display a 50Hz signal or if the additional scan lines would display and thats assuming if it could display at all.

The best thing I could suggest would be to use a component SCART RGB cable - then the only reason you would want an NTSC setting would be to just use 60Hz video timing to get a chip set boost =)

01 August 2016, 22:33	#1
BarryB Amigaholic Join Date: Dec 2009 Location: UK Posts: 4,759	How to switch PAL Rev 6A A500 between PAL/NTSC? Seeing as I have a Rev 6A PAL A500 with a Fat Agnus (8372A), how to switch between PAL/NTSC? Is it as simple as just soldering a switch on JP4? If so, I see a problem with this as one of the pads has almost been obliterated as there is a round hole been made between both pads to cut the connection but has taken off most of the pad near the Agnus chip making soldering extremely unlikely! So, is there any other way to do this, other than the pin 41 mod on the Agnus chip as I'd rather not go that route if possible, plus I've not seen how that mod is done!! I also have an Indi ECS fitted going via VGA to an LCD monitor so 60hz shouldn't be an issue.

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01 August 2016, 23:29	#2
dirkies Zone Friend Join Date: Aug 2002 Location: Belgium Age: 51 Posts: 1,297	U also need to replace the oscillator afaik

01 August 2016, 23:36	#3
BarryB Amigaholic Join Date: Dec 2009 Location: UK Posts: 4,759	Not seen that mentioned for PAL/NTSC switching, for converting permanently a PAL or NTSC Amiga from one to the other then yes, i'd agree the crystal needs changing as well!

01 August 2016, 23:38	#4
dirkies Zone Friend Join Date: Aug 2002 Location: Belgium Age: 51 Posts: 1,297	But what's the point of keeping it ntsc? Oscillator affects timing for demos aswell i read.

02 August 2016, 02:20	#5
BarryB Amigaholic Join Date: Dec 2009 Location: UK Posts: 4,759	But I don't want it NTSC permanently, I want to switch between PAL and NTSC! From what I read the 1mb/2mb Agnus allows this?

02 August 2016, 02:33	#6
idrougge Registered User Join Date: Sep 2007 Location: Stockholm Posts: 4,348	No oscillator needed unless you're running a genlock or something.

02 August 2016, 02:47	#7
ReadOnlyCat Code Kitten Join Date: Aug 2015 Location: Montreal/Canadia Age: 52 Posts: 1,178	The oscillator is needed for code which requires cycle precise synchronization. If you want to be able to switch between PAL and NTSC including oscillators you will need to make a small board with switching logic and plug both oscillators on it. Assuming your motherboard supports dual NTSC/PAL Agnus models you won't need to switch that one but if it doesn't then you would have to switch these too which frankly would be a pain.

02 August 2016, 06:47	#8
TjLaZer Registered User Join Date: Sep 2004 Location: Tacoma, WA USA Age: 52 Posts: 1,927	Don't even bother with a hardware method, just use tools like Degrader, Embedder, PAL/NTSC or BootNTSC/PAL. All on Aminet.

02 August 2016, 20:08	#10
BarryB Amigaholic Join Date: Dec 2009 Location: UK Posts: 4,759	You know, I think i'll just plug my ACA500 back in and do it that way!!

03 August 2016, 14:41	#11
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	In regards to the oscillator this only impacts the NTSC colour encoding while the custom chips run about 20% faster as it keeps timing with the video of 60Hz. European Amiga's have a 50Hz PAL output when you put this in NTSC mode, it is in fact still PAL colour encoding but at 60Hz - interestingly most modern TV's support PAL60, however you do lose a few scan lines at the bottom. I suspect that if you have a NTSC market Amiga then you would be stuck with either 60Hz NTSC or 50Hz NTSC - I don't know how an NTSC TV would display a 50Hz signal or if the additional scan lines would display and thats assuming if it could display at all. The best thing I could suggest would be to use a component SCART RGB cable - then the only reason you would want an NTSC setting would be to just use 60Hz video timing to get a chip set boost =)

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