Teletype 43K001/AAA, Repair Manual

Page: 18 / 82

525,2-4
B. TROUBLESHOOTING (Contd)
1. 43K101 KEYBOARD TROUBLESHOOTING (Contd)
TROUBLESHOOTING GUIDE (Contd)
QUESTION YES
NO
18. Is -12
V
present on pin 2 of circuit
card cable conector P107 (if any
keyswitches light go to Step 18a)?
Go to 18a. Check for open circuit in
cable.
18a. Is -12 V present on pin 4 of key- Go
to
18b. Check for broken or open
switch in question ?
circuit land or defective
solder connection on circuit
board.
18b.
Is
-10
V
or
+5 V
present on pin 3 of
Replace defective key- If voltage is -12 V de, go
keyswitch in question?
switch.
to
19.
19. Is +5 V present on circuit card
Check for broken or open Go to 19a.
cable connection of keyswitch in circuit land to pin 3 of
question?
keyswitch in question.
-
--
-
-
-
--
19a. Is +5 V on the corresponding Check for open circuit in Replace defective keyswitch.
connector pin at P107? cable.
20. Does keyswitch in question meet
the mechanical requirements
(depress and release properly, latch
click, etc)?
,,,
Go to 20a. Replace defective keyswitch.
-
- -
-
-
--- -------
20a. Is keyswitch in question: PRINTER Go to 20b. Go to 21.
TEST, PARITY, Interlock, DUPLEX
or CPS?
20b. Is +5 V present on pin 1 of keyswitch Go to 20c. Check cable for open circuit.
when keyswitch
is
open (released up
position)?
20c. Is 0 V present on pin 1 of keyswitch Go to 29.
Check for open circuit to
in question when keyswitch is
P107 pin 4.
closed (depressed down position)? Check for open connection
at pins of keyswitch.
Replace keyswitch.
21. Are any characters printed when Go to 24.
Go to 21a.
several "data" keys are depressed?
21a. Are supply voltages present on Go to 21b. Check cable for open circuit.
circuit card cable connection?
21b. Is -8
V
present on the cathode Go to 21d. Go to 21c.
ofCR1?
21c. Is -12 V present on the anode
Replace CRl.
Check for open circuit on
of CR 1?
circuit board.
--- --- --
21d. Are supply voltages present at all Check for open circuit on Go to 22.
integrated circuit packs?
circuit board.
22. Are 01L and 02L clocks present
and correct at MLA5 and 01 and
02 clocks present and correct at
MLA1, MLA6 and MLB4? Go to 24. Go to 23.