Maintenance
Troubleshooting
4
4-23
Table 4-6. Troubleshooting Guide (cont)
Test and Symptom Possible Cause/Suggestions
Power Supply (cont)
VDG (voltage between
TP7 and TP8)
≠3.15 ±0.08V
U3, C12, U5
VSS (voltage between
TP2 and common)
≠-5.1 ±0.27V
U4, C21, C23
TP4 ≠1.225 ±0.025V
U3-11 ≠1.0000 ±0.0004V
Hint: if you suspect U3 power
supplies are bad, you can drive the
8062A power supplies externally.
Remove battery, µC pcb, and U3.
Apply +5.2V at TP1 you can then
check the ac converter, diode test
source, VR2, U4, and the power
supply circuitry.
Voltage Test - DC
Gross error (constant
reading of 0.00 or OL)
Perform ratio self-test in dc volts. If
count is good, U3 is good. If count is
way off, suspect U3, C9, R33, R8,
Z3, C16 or C18
Ratio self-test passes,
but constant reading
of 0.00
R1, R2 (fusible resistors replace
with exact equivalent only). RJ1, RJ2,
RJ3, RJ4 (varstors turn yellow when
shorted), open circuit in front end,
bad component is input divider, U3
pins 6 and 7 shorted. (Hint: check
high impedance dc voltage first,
which bypasses the input divider.)
Refer to Table 4-1 for input divide
ratios.
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