https://www.mouser.com/Passive-Components/Fre … 6zu9f?P=1z0wo9y

Hundreds of options there. This frequency is quite common in crystals.

Mouser did supply a suitable crystal once ..but sadly is no longer available ..

"For an Apple II to generate correct color burst, the only part that I have found that consistently works is Vishay/Dale part number XT9UNLANA14M31818. This is available from Mouser (part number 73-XT49U1431-S)."
quote from another site..

and this part is critical ..
for example the mod doesn't work correctly with a parallel resonant crystal of the same frequency..
Phase can be a problem.
harmonics is another issue ..
output amplitude another..
I have at least 3 different crystals of exactly the same frequency that simply dont produce colour or hang the system from different manufacturers.
I could just keep buying and trying..with crossed fingers ..but I was hoping to obtain one that definately works.

I suspect the axis 'Cut' of the quartz is very relevant ..
rgds
VS

Oh I missed the part where the crystal needs to be series resonant. True if you use a parallel in a serial application the frequency will be off by about 10-20KHz, enough to drive the video signal out of spec. Usually that can be remedied by changing the capacitive load of the crystal. The parallel resonant frequency of a crystal is always higher by a few kHz than its series resonance.

stamasd wrote:

Oh I missed the part where the crystal needs to be serial. True if you use a parallel in a serial application the frequency will be off by about 10-20KHz, enough to drive the video signal out of spec. Usually that can be remedied by changing the capacitive load of the crystal.

Thanks for the extra info ..
I guess I could experment with the loading of the crystal..but would rather not if I can go the easier route..

A question from another site ..with an answer supplied..
..and the reason I want the correct xtal..
🤣
"What effect does selecting the wrong capacitance have? Does it skew the frequency, alter the shape of the waveform produced, or something entirely different? Is there an obvious correlation between too low and too high capacitance? Is it a case of slight errors, or orders of magnitude?"

"

May not oscillate.
May not oscillate reliably.
May have low to very low output.
May oscillate on wrong frequency (may be an undertone or an overtone).
For extra points may jump between modes (not usual)
May start up very slowly. And/or not always.
May produce less sinusoidal waveform than expected.
May shatter crystal (not usual in modern applications).

May work perfectly.

Factor of 2 in capacitance usually OK, but not always.
Note that some ceramic cap compositions are far worse in tempco, initial accuracy and general stability than others.

Depends on IC used, layout, how Murphy is feeling and phase of Moon.
Layout can be extremely important. Loop area enclosed by capacitor and crystal leads forma part of the oscillator circuit. Manufacturers often give quite specific advice on crystal and capacitor layout. Note it.

Crystal oscillators approach more closely to analog and to black magic than sane people want to get on a good day. In many cases they "just work" and the arcanery is well hidden. You MAY find that capacitance that is off by a factor or 2 or even 5x still works OK. Or, you may not. When they don't work as hoped they can be most obdurate obstinate obnoxious odious and generally overwhelmingly annoying.
"