Apple IIc monitor that only displays 3/4 of the screen

3 replies [Last post]
Joined: Nov 20 2004
Posts: 42

I have an Apple IIc monitor that only displays 3/4 of the screen.
The right 1/3 of the display fades.
This monitor was like this when I acquired it about 5 years.
No amount of adjustment helps apart from turning up the brightness.
Further, I don't have the circuit diagram.
Please see the attached photo of the screen.
Does anyone have any idea of where to look for the fault, or what the
fault might be? I suspect the horizontal deflection circuitry but would
appreciate advice before powering up the soldering iron.

[img]http://www.applefritter.com/files/images/partial%20IIc%20screen_1.preview.JPG

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Offline
Joined: Jul 5 2016
Posts: 30
Re: Apple IIc monitor that only displays 3/4 of the screen

There is a SAMS technical service manual available online which may assist you. I found there are some minor differences compared to the Australian delivered versions I have but it's still very useful.

If you can't find it let me know and I'll email it to you.

Cheers!

Joined: Nov 20 2004
Posts: 42
Re: Apple IIc monitor that only displays 3/4 of the screen

Thanks Dc99,
I've one of the SAMS books for a IIe only. I cannot locate the one you refer to.
Would you be kind enough to email it?
Perhaps PM me and I can give you my google email address?
Thanks,
Laurie

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Joined: Dec 4 2015
Posts: 44
Re: Apple IIc monitor that only displays 3/4 of the screen

http://apple2online.com/web_documents/Sam's%20Apple%20IIc%20Monitor%20KB.pdf

good possibility is the power supply off the flyback that feeds the CRT
has a bad cap like C517. The ripple is at the horizontal rate which produces the vertical dark band

Larry G