TM 11-5805-424-15/NAVSHIPS 0967-220-9010/TO 31W2-2G-41
c. Troubleshooting Chart Continued
Item
Symptom
Probable trouble
Corrective measure
No.
26
b. Defective amplifier PDA-3 or
b. Check for bit-timing signals at test
PDA-4 on assembly A5 (fig.
jacks J2 and J3 on PC 80034150
take voltage and resistance
measurements PDA-3 (Q5 and Q6
circuitry, fig. 6-33), and replace
defective component. If not pres-
ent at J3, take voltage and
resistance measurements of
PDA-4 (Q7 and Q8 circuitry,
ponents (fig. 6-6).
27
No receive bit-timing signals
a. Defective risetime and falltime
a. Check for bit-timing signals at
available.
shaper No. 1 on assembly A5
TP6 of PC 80034150 (fig. 6-6).
If not present, take voltage and
resistance measurements of
shaper No. 1 (Q9, Q10, Ql11 Q12
circuitry, fig. 6-33); replace de-
fective components (fig. 6-6).
b. Defective amplifier PDA-1 or
b. Check for bit-timing signals at
PDA-2 on assembly A5 (fig.
test jacks J5 and J6 on PC
80034150 (fig. 66). If not pres-
ent at J5, take voltage and
resistance measurements orf
PDA-2 (Q15 and Q16 circuitry,
ponents (fig. 6-6).
28
No external common alarm
Defective amplifier IN-6 on assembly
Troubleshoot amplifier (para 6-7a);
available or no synchronizer,
A12(fig. 811).
replace defective components (fig.
disable output.
the first bistable to the last. The first bistable that has
6-5. Isolating Troubles in Multivibrator Stages
no output is probably defective.
Every bistable multivibrator stage used in the
equipment is essentially the same, only the input
a. Connect the ME-26A/U (set to measure - 30
triggering method is different; therefore, only the
volts dc) between the collector of transistor Qa and
bistable multivibrator stage shown in B, figure 5-1, is
ground.
described below in detail.
To check the other
b. Momentarily short the transistor Qa base to
configurations of the bistable multivibrator stages, follow
emitter. If the collector voltage observed in a above is 0
the same procedures and check the transistors and input
volt, the ME-26A/U should indicate approximately -6
steering diodes. Refer to the appropriate schematic
volts. If the voltage observed in (i above is not -6 volts,
diagram for specific reference designations and
check for open resistor Ra, open diode CRa, or shorted
component values.
Before checking any bistable
resistor Rc.
multivibrator stage, disconnect all signals by removing
c. Connect the ME-26A/U between the collector of
appropriate PC assemblies (refer to the logic diagram
transistor Qb and ground.
d. Check the transistor circuit as described in b
and turn on the power. When several bistables are used
above. If the voltage observed is not -6 volts, check for
in a countdown chain. ascertain which bistable is
open resistor Rb, open diode CRb, or shorted resistor
defective by checking for an output square wave from
Rd.
Change 3
6-53
