Apple II - Characters not being displayed

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Last seen: 6 years 4 months ago
Joined: Aug 14 2014 - 15:34
Posts: 18
Apple II - Characters not being displayed

I finished setting up my Apple II following a move and everything was initially functioning normally.

While keying in commands, some keys started repeating on occasion. Then some keys would repeat several times, followed by one repeating without stopping.

Rebooted to normal prompt. However no matter which key was pressed, no characters were displayed on screen. Reset appears to work normally.

I did find a report of a similar problem in the forums but it did not appear to have been resolved.

This is an earlier Apple II (serial 734) with original keyboard.
Note, my hardware background is limited to pulling/inserting ICs and expansion boards. I no longer own any meters, so very basic instructions (including what meter/settings to use) would be appreciated.

Gord C.

Last seen: 1 day 5 hours ago
Joined: Dec 19 2008 - 21:01
Posts: 394
Re: Apple II - Characters not being displayed

It sounds like your keyboard controller chip died. The MM5740 is very hard to find... The later one is easier and can be replaced with a modern board, I think.

It could also be the couple of 74xx chips on the keyboard, but those only usually ever die if you plug the keyboard into the motherboard backwards, which is not the case here from your description.

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