Tait T855 - Page 187

M850-00 T856/857 Fault Finding C5.11
Copyright TEL 31/09/98
5.7.2 Regulator
N
Y
Check for
overheatin
g
components &
short circuits.
N
Y
Check Q630,
Q620 & IC640.
N
Y
9.0V present
on TP602?
Check Q660 is
switchin
g
at
approx. 150kHz.
N
Y
20V present
on TP603?
Check R615.
Replace IC610.
N
Y
+5V present on
IC610 pin 2?
Key Tx.
Y
Re
g
ulators OK.
N
8.8V present
on Tx re
g
. TP305?
Replace Q610.
Y
N
0V present
on Q860 collector?
Check Q860 and
associated circuitry.
Y
0.6V present on
Q860 base?
N
Re
g
ulators OK.
Check microcontroller
section.
Check continuity
from pin 9 of
D-ran
g
e 1.
13.8V present on
IC630 pin 3?
5.3V present on
IC630 pin 1?
Replace IC630.