Difference with CO16010 and CO61090?

[Jfcatari]

There is a clock difference between these:

 

Both of these appear in 600XL's and 800XL's

 

When I see the CO16010 used, there appears to be this strange setup?

 

Picture taken from a 600XL NTSC.

 

When the CO61090 is used it appears in the expected place with no extra stuff.

 

 

Edited March 25 by Jfcatari
typo

[Kr0tki]

Your numbers don't seem to be correct. In the Atari Engineering Information System Item Master List, the parts are listed as:

C010177    CRYSTAL: 3.579575 MHZ

C016010    CRYSTAL: 3.579545

C061090    CRYSTAL,3.579545 MHX,QUARTZ

and the frequencies are the same in Field Service Manuals for the various computer and console models. So there is apparently no difference in frequencies between the two.

[Jfcatari]

Thanks for the information.

 

I am focused only the C061090 and the C016010.  I have an 800XL that will only work correctly with the C061090.  The composite output to a tube based TV gets a rolling color and B/W picture with the C016010 installed.

 

Do they happen to specify the load capacitance for each? 

 

Maybe they are the same frequency, but the capacitance is different. Like I mentioned above, when I see the  C016010 used is appears between the two crystal locations with the additional component above it.

 

 

 

Edited March 26 by Jfcatari

[Jfcatari]

Here is an 800XL with the same strange setup using the C016010.

 

[_The Doctor__]

It's not strange, they are tuning the frequency by slight. I posted a link about load tuning a crystal, and that's what this is. The frequency of the crystals are not all the same and need to be dialed in for this use.

You can verify the frequencies with a scope for each part number. Do it with and without the capacitor, or a different  capacitor of a slightly different value and watch it change.

Edited March 28 by _The Doctor__

[+kheller2]

Dogpile on the rabbit!

 

The part number description and the crystal both say they are exactly the same. Yet The One needs to be slightly tuned?  I’ll but that but the description shouldn’t be the same. Something EE wise is going on here. 🤔

Edited March 28 by kheller2