Commodore Plus 4 - Page 23

PLUS 4Troubleshooting
Page 44
8) KEYBOARD FAILURES
A) Check
O.K.
••
B) Check
O.K.
••
C) Check
O.K.
••
D) Check
O.K.
••
pins on ribbon cable for good connection
for shorts -CN5, CN6, FB's, Diodes
chip select to U27 and the I.C. U27
Ul for proper operation
If not:
1)
Check socket
2) Check for bad Ul
9) FAILURES IN SOFTWARE MODE -All units should be checked for
proper operation, when any repairs are necessary.
To Check: 1) Press 'Fl' on keyboard
2) Press 'Return' to enter Word Processing mode
3)
Press 'Commodore' key and
'c'
key at the same
••
tIme
4) Type ltc' and press 'Return' to enter
Spreadsheet
5) Press 'Commodore' key and 'C' key again
6) Type 'tw' to return to Word Processing mode
Watch for video or loading problems, then:
A) Check jumpers at JI-J6 for correct connection
O.K•
••
B) Check Ul, U2, U25, U26