Apple IIe - Intermittent random characters displayed on boot

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m_leddleton's picture
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Joined: Aug 4 2017
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Hi everybody, I have just got myself an Apple IIe for the very first time. I have not used anything apple before especially not older stuff so I am still learning the ropes!

I have put a new capacitor in the power supply because that blew up the first time I turned it on. That all seems to work fine so first repair is a success!

Now on to my next task, when I turn on the Apple I randomly get lots of characters on the screen. Sometimes it happens and sometimes not, but it is mainly happening.

NOT FOUND: attached_image_1

Sorry for the poor pictures but It was a struggle taking a photograph of the screen.

I have run the self-test and that comes back with Kernel ok. I have also re-seated all of the removable chips on the PCB.

From what I have read this can be a symptom of faulty or failing ram, can somebody help point me in the right direction for what my next move should be?

EDIT...
Image not working for some reason, how do I get the attached image id?

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applii_errors.jpg47.11 KB

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Joined: Apr 14 2006
Posts: 36
Re: Apple IIe - Intermittent random characters displayed on boot

Hi and congrats on getting your first //e!

The good news is that your Apple appears to be at least 90% OK. The fact that it is starting and showing "Apple II" is a positive sign. The fact that you can run the self test and get the "Kernal OK" message would indicate that the on-board RAM is *probably* OK.

The screens you are showing in your attached image are a result of the machine trying to run some code and dropping into the monitor after hitting errors. The "monitor" is a ROM based utility to view/edit the current execution state (RAM/stack/CPU) and is generally what is called when executing invalid code (bad memory location, invalid CPU opcode, etc).

When you are getting the errors as shown in your attached image, are you trying to boot from a disk? If so, it might be a simple case of either a dirty disk or dirty heads in your disk drive. Does the drive grind at all during boot? If so it lends more probability to dirty disk drive heads. There is at least one video on YouTube demonstrating how to clean a Disk ]['s heads.

The dirty heads can cause these errors due to the code not being read from the disk correctly and then running off the rails during execution.

There could be other causes, but it's probably a good place to start.

Cheers,
Mike