30 31
HOW TO USE TROUBLE-SHOOTING PROCEDURE: Locate the problem on
this table and proceed with the action starting with Step 1. Note, for all DVM
and scope measurements, connect the (-) lead to TP1 (GND).
14.0 700M TROUBLE-SHOOTING AID
700M TROUBLE SHOOTING PROCEDURE
Step Problem Action to be Performed If Correct If Incorrect
1.
Blank
Display*
Measure voltage at U6-19 with
DVM. It should be at +5.0 ±0.25V.
Proceed to
Step 4.
Proceed to
Next Step.
2.
Measure voltage at Q3 output
lead. (The output is the lead near-
est to the edge of the circuit
board).
Check for open
trace between
Q3 and U6-19.
Proceed to
Next Step.
3.
Measure voltage at input of Q3. It
should be 6.5V ±.1V.
Replace Q3. Go to step 8.
4.
Check voltage at TP3. It should be
+5.0V ±0.25V.
Proceed to
next step.
Go to Step 7.
5.
Check Check U4-25 with a scope.
It should be a 3.58MHz square
wave with levels from 0 to 5 volts.
Replace U6. If
still exists, go
to Step 19.
Replace U4. If
still no dis-
play, go to
next step.
6.
Replace Y1 crystal and repeat
Step 5.
Done. Go to Step 19.
7.
No +5
volts or
incorrect
Measure the voltage at Q1 output.
It should be +5.0V ±0.25V. (The
output is the lead nearest to U6).
Check for open
trace on circuit
board.
Proceed to
next step.
8.
Measure voltage at pin 6 of wire
harness. It should be equal to the
battery or power supply voltage.
Proceed to
next step.
Check wire
harness for
broken wires.
9.
Replace Q1 and repeat Step 7. Done. Go to Step 19.
10.
Unit con-
stantly
read -OL-
Measure voltage at U4-28 with
DVM. It should be -4.3 ±0.2V
Go to step 12. Proceed to
next step.
11.
Check voltage at U3-8. It should
be +5.0V ±0.25V.
Replace
U3.
Go to Step 7.
12.
Connect a decade box to the input
and set to 28150 ohms. Measure
voltage at U1-10. It should be
+0.561V ±0.005V.
Go to
Step 14.
Proceed to
next step.
700M TROUBLE SHOOTING PROCEDURE
Step Problem Action to be Performed If Correct If Incorrect
13.
Check voltage at U1-5. It should
be +0.561V ±0.005V.
Replace U1. Go to Step 16.
14.
Check voltage at U2-10. It should
be +1.458 ±0.005V.
Go to Step 19. Proceed to
next step.
15.
Check voltage at U2-5. It should
be +0.578V ±0.005V.
Replace U2. Proceed to
next step.
16.
Check voltage at wire harness at
pin 3 on circuit board. It should
be +0.460V ±0.005V.
Proceed to
next step.
Go to Step 19.
17.
Check voltage at wire harness at
pin 1 on circuit board. It should
be +0.578V ±0.005V.
Go to Step 19. Proceed to
Next Step.
18.
Check for +5 volts, check R1
through R6, R12 and R13. Also
check harness for loose or broken
wires.
Proceed to
next step.
Replace bad
component. If
problem still
exists, pro-
ceed to next
step.
19.
Return unit to factory for repair.
(20 Seiten)
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