721A and the TS-443/U to the test
(b) Dc voltage chart.
probe and adjust for an output of
+dc voltage to
0 volt.
Circuit junction
ground (volts)
I
(2) T u r n TS-1777/VRM-l selection
switch S7902 to position 2.
15.2
P7701-D
15.15
C7710 and R7913
(3) Adjust the PP-2309/U output volt-
6.2
Q7702 base
age to 26 volts dc.
6.5
Q7702 emitter
(4) Increase the 721A output slowly to
7.25
R7912 and R7913
16.1
Q7703 collector
+30 volts dc; observe the voltage on
7.45
Q7703 base
the TS-443/U when GREEN indi-
6.7
Q7703 emitter
cator DS7902 switches on.
200 (rectified
P7701-F
signal)
(5) A normal indication, noted in (4)
above, should be +20.7 volts dc.
(3) Remove the test signal and set the
(a) If the indication obtained is nor-
T S - 1 7 7 7 / V R M - l ON-OFF switch
mal, proceed toe below.
to OFF.
(b) If the indication obtained is not
(4) Replace the faulty part.
normal, proceed to d below.
(5) Repeat f and g above.
d. Schmitt Trigger Isolation.
(1) Remove the test signal from the
59. Isolating Trouble in Assembly A7800
teat probe.
Refer to figure 39 for circuit details and
(2) Measure the dc voltages listed in
the chart below with an ME-26B/U
a. Line Voltage Sensing Circuit Test.
to isolate the faulty part.
(1) Reduce the PP-2309/U output volt-
Untriggered +dc voltage
age to o volt dc
Circuit junction
to ground (volts)
I
(2) Perform adjustment procedure for
t h e line voltage sensing circuit
0.01
Q7802 emitter
15.2
Q7602 collector
given in paragraph 43 b .
1.35
Q7803 emitter
(3) If the circuit does not adjust prop-
6.20
Q7803 collector
erly, proceed to b below.
2.15
Q7804 base
P7801-E
L5
(4) If the circuit does adjust properly,
0.47
Q7805 base
proceed to c below.
0.225
Q7805 emitter
b. Line Voltage Sensing Circuit Iso-
15.2
P7801-D
P7801-F
15.7
lation.
(1) Adjust the PP-2309/U output volt-
(3) Apply +20.7 volts dc to the probe
age to 25 volts dc.
and measure the voltages listed in
(2) Measure the dc voltages listed in
the chart below.
the chart below with an ME-26 B/U
Triggered +dc voltage
Circuit junction
to isolate the faulty part.
to ground (volts)
+dc voltage to
Circuit junction
Q7802 emitter
1.4
ground (volts)
1.32
Q7802 collector
0.64
Q7803 emitter
P7801-B
25
0.72
Q7803 collector
11.3
Q7806 emitter
0.37
Q7804 base
7.9
Q7806 base 1
15.2
Q7601-E
15. 7
17801-C
3.1
Q7805 base
15.3
R7819 and C7802
Q7605 emitter
2.32
15.0
P7801-A
P7801-D
2.9
15. 7
P7801-F
(3) Reduce the PP-2309/U output to
0 volt dc and replace the faulty
(4) R e m o v e the test signal and set
part.
T S - 1 7 7 7 / V R M - 1 ON-OFF switch
(4) Repeat a above.
S7901 to OFF.
(5) Replace the faulty part.
c. Schmitt Trigger Test.
(6) Repeat c above.
(1) Connect Transistor Power Supply
62
