Troubleshooting By Symptom - Facit 4431 Service Instruction

9.8 TROUBLESHOOTING BY SYMPTOM
SYMPTOM CAUSE
High pitched squeal, No terminal Check power supply Check 4MHz
function____ _ ____ clock
Chick
Chick
D42-26 reset line
D42, D49, D50, D48
Set-Up features not retained -23 Volt at D63-2 missing or
(Error code 2) _ _ _ _ _ _ _ _ _ _ D63 bad
Terminal will not communicate
with host _ _ _ _ _ _ _ _ _ _ _ _ Is terminal ON LINE
?
Check Xmit/Rcv
Baud rates, Word lenght, parity
Ch!ck +/-12 Volt
ch!ck D61, D62
Chick clock at D50-7, 8, 9
Printer Port does not work _ _ _ _ _
Check +/-12 Volt
Chick D61, D62
Chick D48
chick D50
Chick V108 (Ptr. Ready)
No Keyboard operation and Cursor
does not blink ___ . ________ Check D50, D42, D72
Ch!ck interrupt priority chain
No video but Be 11 works _______ D57 bad (screen blank)
Bad CRT
Missing dots in characters _ _ _ _ _ Bad Chr. Gen. D15 Bad D39 or D38
shift register
Brightness contra l not working ____ Bad D36
Video attributs wrong _ _ _ _ _ _ _ Bad 12
Bad Prom D57
Double high chars. wrong _ _ _ _ _ _ Bad ROM DB
Bad D18
80 or 132 col. mode nor working _ _ _ Bad osc. select line
t
Baa 80 col .osc.
t
Bad 132 col.osc.
Every row displays same data _ _ _ _ Non-maskable interrupts missing
ERROR CODE 1 check displayed diagnostic:
address Bad IC
8000-87FF D52
8800-BFFF D51
COOO-C3FF D68
C400-C7FF D69
C800-CBFF D67
CCOO-CFFF D66
bad address 8000 suggests buffers D54, D55
bad address COOO suggests D70, D71 , D53
ERROR CODE 4
Replace EPROM D73, D74, D75
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