Apple II crystal question

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Apple II crystal question

OK so I'm working on this Rev-0 board and I think it was modified for PAL.  I don't own a euro system so I have nothing to compare it to.   I removed a whole load of jumpers and other crap on the back and repaired some cut traces.  I got weird video out of it, so I checked the crystal and it was an M-TRON 14.25045 MHz which is wrong for NTSC.

 

I replaced it with a spare no-name 14.31818Mhz crystal but still messed up video....

 

I know the Apple II can be finicky to the brand of crystal.  Since the one Mike Willegal spec'd out for his replica is no longer available, has anyone found another brand of current crystals that are know to work before I do more troubleshooting.

 

Thanks,

Corey

 

 

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Hi Corey,

Hi Corey,

 

This is not about the crystal,  but check that the jumpers aren't bridged over in some spots.

I remember this having something to do with the video timing as well.

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The picky part of the 14

The picky part of the 14.31818 crystals only affects color burst - you will get a correct display, but only in black and white, if the 14.31818 crystal isn't perfectly correct.  Rev-0 boards did not have jumpers for PAL frequency, so you probably still have something to fix.  That 14.25045 crystal was for PAL, so someone probably manually added the later changes for PAL that would be added with cuts and jumpers.

 

regards,

Mike Willegal

 

 

 

 

 

 

 

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Is there a schematic or an

Is there a schematic or an articale on the changes for the Rev-0 for Pal?

Thanks,

Cheers,

Corey

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Well I found some

Well I found some descriptions in Winston Gayler's book.  I'll have to make heads or tails.   If could also be something completely else not related to the PAL conversion.  I guess I better start warming up the oscilloscope after I decipher Winston's book on the subject. 

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I've never seen or heard of a

I've never seen or heard of a rev-0 adapted to PAL, till now.  The main difference is the slightly different timing. I have a monochrome monitor that will display PAL or NTSC Apple II output without problems.

 

regards,

Mike W

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Most monitors, especially

Most monitors, especially period ones don't do both.    With the craziness of the Apple II rev-0 early signal, I'd expect there to be issues even with a PAL monitor.  

 

I took a look at the schematic differences between the PAL Rev-1 and the non-PAL rev-0 board, I'll let you know what I find.  If not it's on to real troubleshooting with a scope... Oh Joy ;-)

 

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