Hello,
I have built my Apple 1 replica so far that I could supply it with power and also connect it to my monitor (Sanyo VM2509). When I turned it on, I noticed that my video signal on the monitor was not centered correctly and the upper part of the screen was displayed in the middle of the monitor. I've tried all the settings on the monitor to center the image correctly, but it didn't work. I also checked the voltage on the IC sockets beforehand and the ICs didn't get hot either. Some were lukewarm, but not to the point of overheating. That's why I'm wondering if anyone else in the forum had a similar problem and can tell me how they solved it.
Thanks for any help
manymaker53
. . . is almost impossible, sorry.
Please post a photo so we can see what it looks like.
- Uncle Bernie
Hi,
I took 2 photos here, the first picture shows the monitor when the Apple 1 is switched on and the 2nd picture shows the screen after it has been cleared.
20241228_215437.jpg
20241228_210034.jpg
Does that display work properly with other video sources?
If so, there may be an incompatibility with the not-quite-standard sync produced by the Apple I (and also the Revision 0 Apple II) which is missing the "serrations" specified by the NTSC.
... to me. If the picture is rolling (up or down), missing VSYNC is almost certain. You can modify the VHOLD control on the monitor to cause rolling, and then, if there is a VSYNC at all, you should see a "blacker than black" horizontal bar which is the VSYNC. If no such bar can be seen in this experiment, the VSYNC is missing. If the bar is there, the VSYNC is misplaced relative to the character field, hinting at some decoding problem, which may involve the three diodes making that wonky DTL gate.
Other than that, there seem to be no major timing problems.
The problem mentioned by 'robespierre' about non standard Apple-1 video would typically manifest as a "lock-in" slant of the first few scan lines (upper left corner of the screen). As there is no sign of that in the picture, it's another clue that the VSYNC may be absent.
- Uncle Bernie
Even when the picture is half way on the screen as seen on the pictures, rotating the V. Hold knob should cause it to start/stop rolling or at least cause it to move up or down a bit. If rotating the V. Hold knob has absolutely zero effect, then the problem is in the monitor, most likely the V. Hold potentiometer.
Hello everybody,
After a long time of trying and trying again, I connected my Apple 1 to my LCD television via a SCART adapter to see whether it also showed the same image. Today I tried this adapter and the image is displayed in an error-free condition. But that also means that the video signal is either not being processed correctly by my monitor or that the monitor has a problem. But I believe in the second one because it occasionally showed distortions in the image, even though I didn't do anything to it. Thank you very much for the many tips and help and I wish you all a happy new year.
Greeting
manymaker53