Macintosh 512ke Keyboard issue

Gamer9430

macrumors 68020
Original poster
Apr 22, 2014
2,229
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Central New Jersey/ North Virginia, USA
So I went to use my 512ke today, but the keyboard doesn't seem to want to work. I've restarted the Mac, unplugged the keyboard and re plugged it in, blew air into the keyboard plug port on both ends, and wiped off the pins of the keyboard cable. It worked the last time I turned it on. It's been unplugged since then, and that was a few months ago. Any ideas as to why this is happening or how to fix it?
 

havokalien

macrumors 6502a
Apr 27, 2006
650
49
Kelso, Wa
does the mouse work? maybe the little clips at each end of the cable are squished down? you didn't try using a regular phone cord did you?
 

Gamer9430

macrumors 68020
Original poster
Apr 22, 2014
2,229
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Central New Jersey/ North Virginia, USA
does the mouse work? maybe the little clips at each end of the cable are squished down? you didn't try using a regular phone cord did you?
The mouse works fine. I was using the original cable, but afterwards I was curious and stuck in a phone cable, but nothing happened, so I went back to the regular cable. After that, after playing with the cable and repeatedly typing, one key would repeat for about 6 times, then stop, and nothing would work still...
 

havokalien

macrumors 6502a
Apr 27, 2006
650
49
Kelso, Wa
Well a regular phone cable will hurt the motherboard.

You can try taking apart the keyboard and replacing any capacitors you find but if you used a regular phone cable it is straight wire and the coiled cable is not. That will put voltage back on itself and hurt the serial chip(or whatever that chip is called)
 

Gamer9430

macrumors 68020
Original poster
Apr 22, 2014
2,229
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Central New Jersey/ North Virginia, USA
Well a regular phone cable will hurt the motherboard.

You can try taking apart the keyboard and replacing any capacitors you find but if you used a regular phone cable it is straight wire and the coiled cable is not. That will put voltage back on itself and hurt the serial chip(or whatever that chip is called)
So I damaged something by using the phone cable...
 

VintageRecapEurope

macrumors newbie
Jun 10, 2015
18
7
Ireland
Hey Gamer9430.
You should use the process of elimination....get your hands on another keyboard, another cable , see if its the same.....if it is then its the motherboard. I do allot of repairs and have allot of macs , keyboards, cables, makes it so much faster to find problems.
you should have a look at the connector for the keyboard cable on the mac itself , use a magnifying glass and check the pins are not damaged.
-
have you opened up the mac to check the motherboard?
 

Gamer9430

macrumors 68020
Original poster
Apr 22, 2014
2,229
1,202
Central New Jersey/ North Virginia, USA
Hey Gamer9430.
You should use the process of elimination....get your hands on another keyboard, another cable , see if its the same.....if it is then its the motherboard. I do allot of repairs and have allot of macs , keyboards, cables, makes it so much faster to find problems.
you should have a look at the connector for the keyboard cable on the mac itself , use a magnifying glass and check the pins are not damaged.
-
have you opened up the mac to check the motherboard?
Thanks! I'm in the process of trying to get another keyboard from someone I know. I will take a look at the pins to see if they are damaged.
I was going to open the motherboard when I first discovered the issue, however I figured I should wait for the electricity to drain out first. I think I'll open it today since its been a few days. Hopefully no capacitors popped. Would I have heard/smelled/saw the capacitor die if it died?
 

VintageRecapEurope

macrumors newbie
Jun 10, 2015
18
7
Ireland
you can open up the mac and remove the motherboard easily.... just be careful of the flyback and the anode cable. Its not rocket science.
have a look at the board - maybey covered in dust, debris.
A good look at the board often tell allot.
 

MacTech68

macrumors 68020
Mar 16, 2008
2,240
167
Australia, Perth
I suspect that the original problem might be the keyboard cable. They were pretty tough but given it's age (and yes, they did break), it's fairly likely.

It's also possible that the two ICs below may need to be reseated in their sockets.

The below assumes you have the short keyboard (the one without the numeric keypad).

However, now that you've used a standard rj11 4p4c cable, it's possible that you've damaged either the 74LS123 or the Intel 8021 inside the keyboard. The 8021 was licensed to Philips as a MAB8021P - I'm not sure if this needs an internal ROM program unique to the Mac, but given that it's numbered with Apple's PN 341-0222B it may be that case.

Right now, a second keyboard (if easily procured as a 'loaner') is pretty vital - if other options like badly bent pins in either the Mac's or keyboard's socket as suggested by @VintageRecapEurope.

If only Apple had foreseen that people might use a reverse wired cable, they could have at least fitted a single diode to protect the keyboard.

Attached is the only clear circuit diagram I can find of the M0110 keyboard.

M0110 Mac 128 Keyboard Circuit Diagram.png
 

Gamer9430

macrumors 68020
Original poster
Apr 22, 2014
2,229
1,202
Central New Jersey/ North Virginia, USA
you can open up the mac and remove the motherboard easily.... just be careful of the flyback and the anode cable. Its not rocket science.
have a look at the board - maybey covered in dust, debris.
A good look at the board often tell allot.
Yeah I've done it before. The floppy drive has a broken eject motor gear which I've yet to replace. My mac is actually updated to 2048MB with an upgrade card, and it also has a SCSI interface on it. I'll open it up and take a look at ok at it. I've cleaned it out before. There wasn't much dust in it, being that the previous owner barely used it and kept it in the carrying case in a closet. I've been leaving it out on a desk, which is probably a bad idea given that it is directly in front of a window.
 
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