Isolating Trouble Within Stage

TM 11-6625-667-45/NAVSHIPS 0969-249-8010/NAVAIR 16-30APM123-2/TO 33A1-3-367-22

Probable trouble

Corrective measures

a. Error gate 1 or 2.----------------- a. Check waveform at test point

Error detector output at teat point

A11TP4. If abnormal, check

A11TP6 abnormal; waveforms

socket resistance at A11Q5 and

were normal at test points

A11Q6; check gate diodes

A10TP6, A12TP4, A11TP1, and

A11CR10 through A11CR13.

A11TP2 during sectionalization

teats.

b. Cheek socket waveforms to insolate

b. Error gate 8 or inverter Transis-

tors A11Q9 and A11Q10.

faulty stage. Check socket resist-

ances at faulty stage.

c. Accept/reject generator DSS3 or

c. Cheek waveform at test point

pulse width adjustment.

A11TP3. If pulse width in

abnormal, adjust control A11R30

to obtain 0.35 +0.01 sec. Check

socket waveforms and resistance

at A11Q7 and A11Q8.

k. Decoder Module A12 Troubleshooting. Transistor socket waveforms are shown in figure 8-23 and

socket resistances are shown in figure 3-18. Test point waveforms are shown in figure 8-36. The schematic

diagram is figure 8-15.

Probable trouble

Corrective measures

Symptom

Error blanking gate or module A9----- Check socket resistance at A12Q11;

Error blanking pulse at test point

A12TP4 abnormal.

if normal, refer to decoder module

A9 troubleshooting chart in i above.

Readout memory DFF5-------------- Check socket waveforms and resist-

Read memory inoperative; error de-

tector output was normal during

ances at transistors A12Q2 and

A12Q3.

sectionalization tests (para 3-4).

Transistor A12Q4, A12Q5, or A12Q6,

Reply evaluator output at test

Check socket resistance of transistor

capacitor A12C8, or adjustment of

point A12TP1 abnormal (7 to 12

and cheek capacitor A12C8. If nor-

the reply evaluator.

vdc).

real, perform adjustment in para-

graph 4-5e.

Transistor A12Q7, A12Q8, A12Q9, or

No accept or reject indication, but

Check socket resistances of transistors.

A12Q1O.

reply evaluator is normal.

Paragraph 3-8e contains information that maybe

3-7. Isolating Trouble Within Stage

helpful in isolating trouble with the transistors

a. General. When trouble has been localized to

wired in the circuit.

a stage during troubleshooting (para 3-6), isolate

c. Wiring Diagrams. Use the wiring diagrams

the defective part by voltage measurements or re-

(figs. 8-24 through 8-35s) to circuit trace and iso-

sistance measurements; use the figure referenced

late the faulty part.

in the corrective measures column.

Caution: Before attempting to perform

3-8. Analysis of Measurements

voltage and resistance measurements, refer to

a. In-Circuit Transistor Resistance Measure-

paragraph 3-2e and 3-8. Carefully follow in-

ments. When measuring resistance of circuit ele-

structions and observe notes on voltage and

ments connected across the junctions of any tran-

resistance diagrams.

sistor (base-emitter or base-collector), consider

Carelessness may cause more troubles in the equip-

polarity of the ohmmeter and try measurements

ment and make the troubleshooting job more diffi-

with the ohmmeter connectd one way, and then

cult. Do not remove or insert a transistor with

reverse the leads. Also consider that different val-

voltage applied to the circuit..

ues of resistance will be obtained with the ohm-

b. Transistor Testing. The transistors are wired

meter on different ranges. As an example, if the

in the circuit; therefore. every effort should be

transistor junction or a resistor plus the transistor

made to troubleshoot the equipment without physi-

junction is measured in the forward direction of

cally unsoldering and removing the transistors.

the RX10 range, the actual reading will be less

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