apple iic checkerboard pattern problem

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apple iic checkerboard pattern problem
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Image icon checkerboard pattern1.87 MB

Hello, i need help ?

After few weeks i didn't turned on my IIC it start's with out beep with only checkerboard pattern like that.

With or without the keyboard connected same pattern.

I already get out all the CPU / ROM and other socket's chips and put them back in and nothing...

I did piggybacking to all the RAM IC's but nothing.

the light on the keyboard is on but nothing happend when i press it. when i press the reset sequence sometimes it change a little bit the pattern but it's not always.

 

Any idea what can it be ?

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That pattern is indicative of

That pattern is indicative of a CPU that has not started up.

It could be variiuos things - the CPU, the ROM, RAM, or something else.

You have video, so the clock is working, but the CPU has not initialized the video chip.

Since this worked prior to storage I would remove all socketed chips, clean the pins with some contact cleaner and a cotton swab and re-insert them into their sockets.

That might be all it is, but you could also try and get the machine to run it's internal system test (power up with both the closed apple key pressed - or power up with the keyboard disconnected) although if it is showing the checkerboard then it might not be able to run the self-diagnostic.  I would still try, though.

 

 

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nothing yet

baldrick thank's 

Unfortanatly i already did that , nothing has changed the pattern i get. i also changed the ROM to another one. 

I didn't manage to start the self diagnostic.

 

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Replace the CPU next.

Replace the CPU next.

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Do you have a Scope

So that you can check the CPU's clock signal, address bus, data bus, etc.?

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i replaced the CPU but nothing

i replaced the CPU but nothing

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It's most likely a RAM issue.

It's most likely a RAM issue. Piggybacking won't always work on a dead RAM chip. Without a scope or advanced troubleshooting skills, you might have to socket all of the RAM so that you can easily swap chips. Or, if the ROMXc is worth it to you (or you can borrow one), then use its Recovery mode to run a dead RAM test. It will beep out the position of any bad chips.

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