Heathkit IO-4205 - Page 192

TEST #1
+9 VOLTS AND +5 VOLTS POWER SUPPLY
'
:These supplies track each other. If
upply fails, the other will also shut
Measure the voltage at points
Q and V on the power
~
supply circuit board.This voltage should be - 9 volts.
Diodes D303,
D304, D305, D306 incorrectly
~
Measure the voltage at pin 4 of integrated circuit
~
in stalled or faulty. Resistors R3 02, R303 incorrect
~
U303. This voltage should be -15 volts.
. ..... .. ..
valu e. Capacitors C304, C305, C306, or C307
,3>
Measure the voltage at pin 1 of integrated circuit
~
incorrectly installed or faul ty . Check power
U302. This voltage s
hou ld be +1 5 volts.
transformer windings C-AB and E-AB for
10 volts
Measure the voltage at points P and U on the power
AC.
supply circuit board. This voltage should be
+9 volts.
~~
Check for solder bri dg es between foils on the other
~
circuit
boards.
R
es istors
R~34 ,
R335, R336
incorrect value. Capacitors C310,
C311 incorrectly
Integrated circuit U302 or U303 defective.
~
installed or faulty.
Measure the voltage
at points N, T, and AH on the
~
6>
Integrated circuit U301 defective.
Measure the voltage at pin 1 of U301. This voltage
power supply circuit board. This voltage should be
C309 incorrectly installed or defective. Check for
+5 volts.
h/
should be + 15 volts.
solder b
ri dges between foils on the other circuit
boards.
~E?
Measure the voltage at point J on the power supply
8>
Diodes
D307,
0
308 ,
D309, .
0310
incorrectly
circuit board. This voltage should be + 170 volts.
installed or faulty. Check power transformer
T1
winding F-G for 1 20 volts AC.