Specifications

(b) Dc voltage chart.
Circuit junction
I
+dc voltage to
ground (volts)
P7701-D
C7710 and R7913
Q7702 base
Q7702 emitter
R7912 and R7913
Q7703 collector
Q7703 base
Q7703 emitter
P7701-F
15.2
15.15
6.2
6.5
7.25
16.1
7.45
6.7
200 (rectified
signal)
(3)
(4)
(5)
Remove the test signal and set the
TS-1777/VRM-l ON-OFF switch
to OFF.
Replace the faulty part.
Repeat f and g above.
59. Isolating Trouble in Assembly A7800
Refer to figure 39 for circuit details and
figure 33 for aid in locating the parts.
a. Line Voltage Sensing Circuit Test.
(1)
(2)
(3)
(4)
Reduce the PP-2309/U output volt-
age to o volt dc
Perform adjustment procedure for
the line voltage sensing circuit
given in paragraph 43 b.
If the circuit does not adjust prop-
erly, proceed to b below.
If the circuit does adjust properly,
P7801-E
proceed to c below.
b. Line Voltage Sensing Circuit Iso-
lation.
(1) Adjust the PP-2309/U output volt-
age to 25 volts dc.
(2) Measure the dc voltages listed in
the chart below with an ME-26 B/U
to isolate the faulty part.
Circuit junction
Triggered +dc voltage
to ground (volts)
Circuit junction
+dc voltage to
ground (volts)
P7801-B 25
Q7806 emitter
11.3
Q7806 base 1
7.9
17801-C
15. 7
R7819 and C7802
15.3
P7801-A
15.0
(3) Reduce the PP-2309/U output to
0 volt dc and replace the faulty
part.
(4) Repeat a above.
c. Schmitt Trigger Test.
(1) Connect Transistor Power Supply
(2)
(3)
(4)
(5)
721A and the TS-443/U to the test
probe and adjust for an output of
0 volt.
Turn TS-1777/VRM-l selection
switch S7902 to position 2.
Adjust the PP-2309/U output volt-
age to 26 volts dc.
Increase the 721A output slowly to
+30 volts dc; observe the voltage on
the TS-443/U when GREEN indi-
cator DS7902 switches on.
A normal indication, noted in (4)
above, should be +20.7 volts dc.
(a) If the indication obtained is nor-
mal, proceed toe below.
(b) If the indication obtained is not
normal, proceed to d below.
d. Schmitt Trigger Isolation.
(1) Remove the test signal from the
teat probe.
(2) Measure the dc voltages listed in
the chart below with an ME-26B/U
to isolate the faulty part.
Circuit junction
I
Untriggered +dc voltage
to ground (volts)
Q7802 emitter
Q7602 collector
Q7803 emitter
Q7803 collector
Q7804 base
Q7805 base
Q7805 emitter
P7801-D
P7801-F
0.01
15.2
1.35
6.20
2.15
L 5
0.47
0.225
15.2
15.7
(3) Apply +20.7 volts dc to the probe
and measure the voltages listed in
the chart below.
Q7802 emitter
Q7802 collector
Q7803 emitter
Q7803 collector
Q7804 base
Q7601-E
Q7805 base
Q7605 emitter
P7801-D
P7801-F
1.4
1.32
0.64
0.72
0.37
15.2
3.1
2.32
2.9
15. 7
(4)
(5)
(6)
Remove the test signal and set
TS-1777/VRM-1 ON-OFF switch
S7901 to OFF.
Replace the faulty part.
Repeat c above.
62