Teletype 43K001/AAA, Repair Manual

Page: 30 / 82

525,2-16
B. TROUBLESHOOTING (Contd)
3. 43K001 RO KEYBOARD TROUBLESHOOTING (Contd)
TROUBLESHOOTING GUIDE (Contd)
QUESTION YES
lOc. With MLA3-11 and 8 connected
Go to lOd.
to GND, are MLB2 and MLB3
counting in binary?
lOd. With MLA3-11 and 8 connected to Go to lOe.
GND, are waveforms at MLB4-12
and 10 present and correct?
lOe. With MLA3-11 and 8 connected
Check START LATCH
to GND are pulses present on Replace MLB4.
MLA2-8?
11. Is 0
V
present on INTERLOCK
Check cable for open
SWITCH, pin 1 when INTERLOCK circuit.
SWITCH is closed (depressed)?
12. Is trouble present but not defined Undefined trouble -
by question 1 through 11? refer to Circuit Descrip-
tion and Diagrams, etc.
NO
Check ADDRESS COUNTER.
Replace MLB4.
Replace MLA2.
Replace defective keyswitch.
Review initial indication
of trouble.
Note: Remove GND from MLA3-11 and 8 after correcting trouble (if strapped in Step lOb).