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Apple IIc constantly registering key presses

I

itsvince725

Experienced Member
Joined
Nov 26, 2016
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446
Location
Pennsylvania
I picked up an Apple IIc a few days ago and it has a very strange problem: as soon as the system has booted far enough to register key presses, the screen quickly becomes filled with them, all without me touching the keyboard. No keys seem to be stuck so I have no idea why this is happening, this is the first Apple II I've ever owned so I'm not experienced in troubleshooting them.

PXL_20220214_140537764.jpgPXL_20220214_140632846.jpg
 
I have seen this with horribly dirty keyboards. There are two things you can do. get to the point the keys are pressing themselves then remove the keyboard connector from the board while its running (yes you will have to cover off first. If the typing stops is the keyboard. Run it through the dishwasher with the dry cycle turned off. Allow it to fully dry (may take days), then try again.
 
oldpcguy said:
What happens if you hold down CTRL and RESET?
Click to expand...
Nothing, it just does the same thing. I actually was pressing that to try and run a PEEK command that tells me the ROM version and then I realized the keyboard had a mind of its own.

I will have to try testing with the cover off and pulling the keyboard.
 
VERAULT said:
I have seen this with horribly dirty keyboards. There are two things you can do. get to the point the keys are pressing themselves then remove the keyboard connector from the board while its running (yes you will have to cover off first. If the typing stops is the keyboard. Run it through the dishwasher with the dry cycle turned off. Allow it to fully dry (may take days), then try again.
Click to expand...
While worth a try the IIc enters some sort of exercise mode (at least ROM 255 which doesn't have the built-in self-test) when the keyboard is disconnected.
 
Since it's apparently producing random key presses, I'd assume it's probably the keyboard controller, not the keyboard itself.

Im assuming its the big black square keyswitches with the hairpin spring on them? Those are the worst.
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True. My IIc has that keyboard as well. I completely removed the springs and the rubber pad, which made the keyboard a million times better. :)
 
Again, I have had amazing luck with using the dishwasher to remove grit from IIc keyboards which most deemed irreparable. Remember the detergent has anticorrosives for metal.
Im not the only one who uses this method:
 
I watch a lot of Adrian's repair videos as I learn a lot of ways to do things (like cleaning keyboards). I don't use a dishwasher because I have an ultrasonic cleaner which I would use instead.
 
I understand that, but it doesnt have anti-corrosives. To be honest I dont own an ultrasonic cleaner, but from videos I have watched I am not too impressed by how things look when they come out. We pretty much do all our dishes by hand so the dishwasher doesnt get much use... And I dont really like the brand anyway. So using it to clean some PCB's is fine. I have gotten battery burned boards to sparkle,.,, Grimey CRT boards to look (and smell) new again. Nicotine covered systems clean and without the smell. And Lke I mentioned it removed some types of corrosion especially in keyswitches. I used to pop each switch open and clean and rebuild. Now I use the dishwasher and worst case I may have one or two switches that still need special attention.
 
I was not advocating against using a dishwasher. I am saying that I don't use one as I have an ultrasonic cleaner (which can be used with a variety of different cleaning agents, it's not limited to just plain water).
 
Timo W. said:
Since it's apparently producing random key presses, I'd assume it's probably the keyboard controller, not the keyboard itself.


True. My IIc has that keyboard as well. I completely removed the springs and the rubber pad, which made the keyboard a million times better. :)
Click to expand...

What chip is the keyboard controller? I don't own an oscilloscope so I probably can't do much to troubleshoot it.
 
itsvince725 said:
What chip is the keyboard controller? I don't own an oscilloscope so I probably can't do much to troubleshoot it.
Click to expand...
It's UB16, the 40-pin chip to the very left front of the system (when viewed from the front).

Without test tools and / or spare parts the best I can recommend you do is remove and reseat any socketed chips and thoroughly (perhaps use a dishwasher as recommended) clean the keyboard.
 
id be pretty darn surprised if its a kb controller failure on a iic. I have fixed a couple dozen iics at this point and never seen the kb controller fail.. Now the IIe kb controller. thats another story. I have seen keyboards on iies and iics type keys at random. most times its really really dirty machines and the key switches are corroded... or have liquid in them.
 
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VERAULT said:
id be pretty darn surprised if its a kb controller failure on a iic. I have fixed a couple dozen iics at this point and never seen the kb controller fail.. Now the IIe kb controller. thats another story. I have seen keyboards on iies and iics type keys at random. most times its really really dirty machines and the key switches are corroded... or have liquid in them.
Click to expand...
I had thought there might be a liquid issue when I started the system the first time after a healthy Magic Eraser scrubbing, but when it exhibited the same behavior completely dry, I knew that wasn't the problem.
 
VERAULT said:
id be pretty darn surprised if its a kb controller failure on a iic. I have fixed a couple dozen iics at this point and never seen the kb controller fail.. Now the IIe kb controller. thats another story. I have seen keyboards on iies and iics type keys at random. most times its really really dirty machines and the key switches are corroded... or have liquid in them.
Click to expand...
And I have never had a single Mac destroyed by a leaked battery. Problem is, personal experience does not mean the same is true for all others. Unlike you, I never had any keyboard with liquid damage either. Point is, it can be the keyboard or the controller and neither should be ruled out from the outset based on "personal experience".

A broken keyboard ICs is not uncommon on the IIc. You can find repair videos on YouTube dealing with exactly that issue.
 
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