Amiga 1000 NTSC to PAL conversion.

[arttu80]

Hi all!

Recently I've got one NTCS Amiga 1000 (REV A motherboard) in my posession, but it doesn't boot, only blinking turquoise screen. The problem is, it doesn't have NTSC -agnus chip but PAL version. So I'm suspecting compatibility problem here. I already replaced oscillator from PAL A2000 machine in hope it will cope with PAL agnus, but it won't. So does somebody know, can I convert this to full PAL A1000? Some hacking required?

As a little side note, this motherboard have one memory chip installed in soldered socket and it is of different manufacturer from 7 others. Original RAM chips are Nec D41464C-15 and this socketed one is Hitachi HM50464P-15 (in U2E location). I believe they are compatible? Can this be the symptom for blinking turquoise screen?

I relly would enjoy this machine being rescued, but I need help!

[mechy]

To my knowledge, all that is needed for PAL is the agnus and the proper oscillator.
it sounds like someone has just replaced a bad ram chip.

bad ram could possibly give the symptoms you see.

Are you sure the agnus is a good part? The oscillator the proper one?
mech

[Zac67]

An NTSC Agnus works fine with a PAL oscillator (and vice versa). Swapping the latter is only necessary for 100% timing compatibility when using external video equipment.

All 4x 64K RAM chips should work AOK, there's no problem in mixing them (as long as they're working and fast enough).

Blue boot screen is reported to indicate chipset failure, arbitrary color may indicate catastrophic RAM failure and/or chipset failure. (I got a purple screen once when the oscillator had popped out of its socket.) If you've got the spares I'd try swapping the core chipset, the CIAs, MPU and then the RAMs.

I guess you've made sure all socket contacts and voltages are OK? Any bulged/leaked capacitors? Check if any of the PALs or the RAM chips feels very hot, this can sometimes be a quick guide.

[arttu80]

Thank you for answers. I couldn't make any difference at this point, but is there any way to diagnose those "74LSxxx" logic chips while they're on motherboard, using multimeter? I measured voltages at power supply and disk drive connectors, they're fine, but is there some other useful points on motherboard, where I should measure these values? Any help appreciated!