Apple IIc keyboard issue

[mrcribbs]

In my quest to restore an Apple IIc I aquired I am having an issue with the keyboard. The up arrow key is not working. I replaced the key switch with a known good one and it still does not work.

Does anybody have any schematics or insight so I can troubleshoot? It seems odd that only one key wouldn't work.

 

[oldpcguy]

I was unable to find a keyboard matrix specific to the IIc. I have one from a IIe and, given they're similar, the following is based on that. The first thing I would ask you to do is check to see how close, if any, the IIe matrix is to the IIc.

For the IIe the up arrow key shares in common the space and carriage return key on pin 26 (of the keyboard cable) and the down arrow, P, +/=, </,, K, U, and &/7 key on pin 25. If you have a meter I would recommend first seeing if this holds true for the IIc.

 

[mrcribbs]

I've read that the IIe uses a 26 pin cable but the IIc uses a 34 pin. I've found this but I'm unsure how to decipher it.


Keyboard matrix

X0 1 2 3 4 5 6 7 8 9
Y0 ESC 1 2 3 4 6 5 7 8 9

1 TAB Q W E R Y T U I O

2 A D S H F G J K ; L

3 Z X C V B N M < > ?

4 \ + 0 -

5 ~ P [ ]

6 RET UP SPC "

7 DEL DN LT RT


Matrix
J9

X0 31
1 24
2 22
3 8
4 14
5 6
6 10
7 1
8 4
9 2

Y0 12
1 33
2 18
3 20
4 3
5 5
6 7
7 9

NC 13
17
30

GND 21

SFT 34
CTL 32
CMD 16
CMD 26
CAPS 28


J9 pinout
1 X7
2 X9
3 Y4
4 X8
5 Y5
6 X5
7 Y6
8 X3
9 Y7
10 X6
11 DISK LED (5v)
12 Y0
13 NC
14 X4
15 KEYBOARD SW
16 CLOSED APPLE
17 NC
18 Y2
19 40/80 COL SWITCH
20 Y3
21 GROUND ???
22 X2
23 GROUND ???
24 X1
25 POWER LED (5v)
26 OPEN APPLE
27 LED GROUND ???
28 CAPS LOCK
29 RESET
30 NC
31 X0
32 CONTROL
33 Y1

 

[oldpcguy]

I've read that the IIe uses a 26 pin cable but the IIc uses a 34 pin. I've found this but I'm unsure how to decipher it.


Keyboard matrix

X0 1 2 3 4 5 6 7 8 9
Y0 ESC 1 2 3 4 6 5 7 8 9

1 TAB Q W E R Y T U I O

2 A D S H F G J K ; L

3 Z X C V B N M < > ?

4 \ + 0 -

5 ~ P [ ]

6 RET UP SPC "

7 DEL DN LT RT


Matrix
J9

X0 31
1 24
2 22
3 8
4 14
5 6
6 10
7 1
8 4
9 2

Y0 12
1 33
2 18
3 20
4 3
5 5
6 7
7 9

NC 13
17
30

GND 21

SFT 34
CTL 32
CMD 16
CMD 26
CAPS 28


J9 pinout
1 X7
2 X9
3 Y4
4 X8
5 Y5
6 X5
7 Y6
8 X3
9 Y7
10 X6
11 DISK LED (5v)
12 Y0
13 NC
14 X4
15 KEYBOARD SW
16 CLOSED APPLE
17 NC
18 Y2
19 40/80 COL SWITCH
20 Y3
21 GROUND ???
22 X2
23 GROUND ???
24 X1
25 POWER LED (5v)
26 OPEN APPLE
27 LED GROUND ???
28 CAPS LOCK
29 RESET
30 NC
31 X0
32 CONTROL
33 Y1

X and Y are pins on the keyboard controller which are used to determine which key is pressed. The up arrow key, when pressed, will connect one of the X lines to one of the Y lines...which is defined by the keyboard matrix. Unfortunately I cannot decipher the keyboard matrix you provided to determine which X and Y combination. Where did you obtain the matrix?

 

[mrcribbs]

I found this in a google search and what I posted was in a google drive document. There were links to two applefritter website pages but both links are dead.

 

[oldpcguy]

I found this in a google search and what I posted was in a google drive document. There were links to two applefritter website pages but both links are dead.

My recommendation would be to use your meter and trace each side of the key switch to one of the X or Y pins. One side should go to an X and the other to a Y. Put one meter probe on one of the key switch pins and run down the X and Y pins on the keyboard connector (on the keyboard side). The information you posted indicates which connector pins represent an X or Y connection. Then repeat the process for the other side of the key switch. If either one doesn't show continuity then there's a high probability the connection from the key switch to the keyboard connector is the issue.