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Compact with Apple IIc (green) CRT - centreing?

Posted by: Byrd on 2021-10-23 22:52:34

Hi all,

I've had an Apple IIc (green) CRT stored away for some time, and thought about putting it in one of my Compacts. It has the yoke assembly from a Mac Classic for easy transplant.

Here it is installed in an SE/30 - the picture is stable, but the image is not centred well. The "Classic Mac Repair Notes" PDF notes adjusting the centreing rings on the yoke; does this sound right - has anyone else adjusted same? I've only ever dabbled with yoke rings in an arcade monitor and it was a nightmare, just wanted to double check.

Thanks

JB

Posted by: bibilit on 2021-10-24 02:35:48

There is more than that.
Those two rings will allow centering the image on both axis, but from your picture there is also a geometry issue on top of the screen.
IIRC you should also turn one of the upper magnet to get it corrected

Posted by: chillin on 2021-11-02 18:03:23

I did the same swap with an SE/30... uh, 17ya.
Good info here:

Mac Se Crt Adjustment - Apple Macintosh SE 30 - Mac Repair Central

Awarning This product Analog Board contains high voltage and a high-vacuum picture tube. To prevent serious personal injury or equipment damage, review the CRT

www.macrepaircentral.us

and especially here (the previous page):

Yoke - Apple Macintosh SE 30 - Mac Repair Central

Awarning This product contains high voltage and a high-vacuum picture tube. To prevent serious injury, review CRT safety in Bulletins Safety. Warning Because

www.macrepaircentral.us

The description you posted from Lee's Classic Mac Repair Notes is exactly right. It is a trial and error adjustment and very dangerous to do while the machine is naked and running, but that is how it is done. Though as Lee suggests, use a non-conducting instrument that is long enough to keep your hands out of danger to make your adjustments.

Here is a better picture of these rings (arrows just for indication, not necessarily rotation):

Posted by: Byrd on 2021-11-02 18:28:07

Thanks @chillin for the info - I ended up shelving my green CRT for another day, as the B&W display I had was in really good condition and not worth the time spent removing. But I know that what I have works and with some adjustment of magnets, plates would be good in another Mac.

Posted by: chillin on 2021-11-02 18:39:05

I always liked green monochrome monitors. Maybe it isn't the best fit for running System 6 or 7, which looks better in B&W than in green mono, but I like it for running NetBSD without a GUI. I never did figure out how to permanently invert the colors to green on black rather than black on green. I know it can be done within screen (screen manager with VT100/ANSI terminal emulation), but the screen manual is like 40 pages long.

When you do get around to your swap, make sure you restore the IIc monitor with the B&W CRT from the Mac. No point in leaving good parts go to waste,