Only blinking @ characters after CLS

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Only blinking @ characters after CLS

Hi,

I follow this great forum for a while now and decided to build an Apple 1 clone too.

After gathering the components all around the world, I finally reached the point where I could start the build. Everything worked fine at the beginning, but I am stuck now I guess. With all this vintage components and no logic analyzer, it is pretty though to search for errors.

 So I built the terminal section piece by piece following the advice found here in the forum. I reached the point where, when I switch on the clone, the  _@ characters appear. The @ is flashing. This is fine I guess.

Now when I press CLS, I only get a screen full of @ characters flashing. Nothing alse works from this point on. Reset does not work and I never got a single @ sign on the top left.

I already changed most components without any luck.

I also build a Keyboard and added the components for the computer section. Neither solved the issue.

An observation I made is, that if I power down the clone and turn it on immediately I receive random charaters on screen and the video output looks very noisy. I read that the random characters  are normal behaviour.

Do you have any advice for me how to approach this issue?

Thank you very much.

 

 

 

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Last seen: 10 hours 12 min ago
Joined: Oct 9 2011 - 12:54
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If you search here, there are

If you search here, there are a lot of suggestions... But I'll start with the most obvious ones since this is the processor section not seeming to reset. Check your soldering on the back of the board for cold solder joints, bridges and such. Reseat all the chips in the processor section to make sure no legs are bent under (also double check your PROMs are in the right socket and not reversed). Also try pulling all your ram, while the monitor won't work, if there is a bad ram chip screwing something up the monitor software, the monitor will run without ram till it prints the first \ but will crash when it tries to return back to the calling code before it prints the . You will then you know you have a RAM or addressing problem.

Cheers,
Corey

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Joined: Sep 22 2019 - 06:35
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Thanks for the hints, Corey!

Thanks for the hints, Corey!

Do I understand correctly, that a screen full of @ characters is normal behaviour, if only the terminal section is built and CLS is pressed? I thought only one @ character appears in the top left corner of the screen.

Concerning the PROMs I am not sure if they were burned correctly. This is a potential source of error I guess.

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Technically, yes if the

Technically, yes if the terminal section alone is populated it should clear the screen when you press clear.  However if you have the terminal section populated, you can get weird behavior if the terminal section has an issue or if there is a solder bridge or something else.

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