Advice - Have you seen a monitor do this?

[Simon Johnson]

This Amdek monitor has a double image showing. It also appears to have missing lines, per the second image. Has anyone encountered this before?

I know its the monitor, because if I plug the computer into a TV it’s fine. I found the service manual here: https://archive.org/details/cmt-3-2 but I'm having trouble understanding it all.... thats the extent of my knowledge. Any help would be much appreciated.

Castle Wolfenstein on the Apple II Europlus.

 

[skate323k137]

Almost looks visually akin to an incorrect sync frequency, like 24k vs 15k.

 

[Plasma]

I'm guessing the Apple II Europlus is PAL and that monitor is NTSC.

 

[Simon Johnson]

I'm guessing the Apple II Europlus is PAL and that monitor is NTSC.

I believe the EuroPlus is NTSC. It had a PAL encoder card, which I removed. One of the chips on the card was CRAZY hot. I can't get the card to work, cant find a manual for it and have no idea where that connector goes to.

Aside from the card, the video out works well to another CRT.

 

[Plasma]

Is the main crystal 14.25 MHz or 14.318?

 

[Simon Johnson]

Is the main crystal 14.25 MHz or 14.318?

Is that info visible on the motherboard or do I have to measure it?

 

[hard_fault]

After reading this thread, it has dawned on me what might be occurring whenever I run a particular demo on my Apple IIGS. The screen ends up looking very similar to what you're showing, but on an Apple IIGS monitor, after trying to run a certain demo on it. Thought my monitor was toast, even went as far as pulling it apart to inspect the electronics inside. What resolved this issue was temporarily disconnecting/reconnecting the motherboard battery. I have 2 Apple IIGS monitors and a spare motherboard now because of this.

That demo I tried to run must have been setting some bits to drive the vertical at 50hz, and disconnecting the battery reverts it back to 60hz. If anyone believes I'm wrong on this, feel free to correct me. Currently trying to sort through old documents to find my answer.

 

[Simon Johnson]

After reading this thread, it has dawned on me what might be occurring whenever I run a particular demo on my Apple IIGS. The screen ends up looking very similar to what you're showing, but on an Apple IIGS monitor, after trying to run a certain demo on it. Thought my monitor was toast, even went as far as pulling it apart to inspect the electronics inside. What resolved this issue was temporarily disconnecting/reconnecting the motherboard battery. I have 2 Apple IIGS monitors and a spare motherboard now because of this.

That demo I tried to run must have been setting some bits to drive the vertical at 50hz, and disconnecting the battery reverts it back to 60hz. If anyone believes I'm wrong on this, feel free to correct me. Currently trying to sort through old documents to find my answer.

I'll have a look into it. Better than everything else I've tried !!! Thank you.