Agilent Technologies E3620A Manual De Funcionamiento Y Servicio página 84

SYMPTOM
High output voltage 1. Attempt to turn off Q1 by
(higher than rating) shorting emitter-to-col-
lector of Q6.
2. Measure voltage at
base of Q6.
Low output voltage 1. Attempt to turn on Q1 by
(lower than rating) disconnecting emitter of
Q6.
2. Attempt to turn off of Q6
by shorting point
3. Eliminate current limit
circuit as a source of
trouble by disconnecting
anode of CR9.
4. Measure voltage at pin 3
of U10.
STEP ACTION
Set output voltage at 16V.
1 Measure the voltage for pin 7 of U18.
2 Measure the voltage for pin 1 of U3.
STEP ACTION
Set output voltage to 10V ± 1V.
1 Measure the voltage for pin 1 of U4.
2 Measure the voltage for pin 1 of U6.
3 Measure the voltage for pin 1 of U7.
4 Measure the voltage from pin 6 to pin
7 of U7.
Set output voltage to 19V ± 1V.
5 Measure the voltage for pin 7 of U4.
Table A-6. V2 Supply Troubleshooting
STEP - ACTION
a. Output voltage remains high.
b. Output voltage decreases.
a. Measured voltage is more than 0
b. Measured voltage is less than 0
a. Output voltage remains low.
b. Output voltage increases.
a. Output voltage remains low.
b. Output voltage increases.
to +12 V.
a. Output voltage increases.
b. Output voltage remains low.
a. Measured voltage is near
b. Measured voltage is zero volt.
c. Measured voltage is near
Table A-7. V1 Preregulator/Control Circuit Troubleshooting
a. Measured voltage is -12V.
b. Measured voltage is near
a. Measured voltage is near +1V
b. Measured voltage is near 0V.
Table A-8. V2 Preregulator/Control Circuit Troubleshooting
a. High voltage(+0.7 V).
b. Low voltage(0 V).
a. Low voltage(-12 V).
b. High voltage(+12 V).
a. High voltage(+12 V).
b. Low voltage(-12 V).
a. Measured voltage is positive.
b. Measured voltage is negative.
a. High voltage(+0.7 V).
b. Low voltage(0 V).
RESPONSE
volt.
volt.
+0.7V.
-0.7V
RESPONSE
+11.3V.
RESPONSE
A-9
PROBABLE CAUSE
a. Q1 shorted.
b. Remove short and proceed to step
(2).
a. Check for open CR8 or R48 and
check for defective U10B.
b. Check for defective Q6.
a. Q1 open.
b. Re-connect the emitter lead and
proceed to step (2).
a. Q6 shorted.
b. Remove short and proceed to step
(3).
a. Check for U10A defective.
b. Reconnect lead and proceed to
step (4).
a. Check for defective U10B.
b. Check for shorted CR14 and
CR15.
c. Check for shorted R48, or leaky or
shorted C9.
PROBABLE CAUSE
a. Proceed to step (2).
b. Check for defective U18B.
a. Check for defective U3 or Q5.
b. Check for open Q9 or R6.
PROBABLE CAUSE
a. U1 or Q3 defective.
b. Proceed to step 2.
a. U4 defective.
b. Proceed to step 3.
a. U6 defective.
b. Proceed to step 4.
a. U7 defective.
b. U5 defective.
a. U2 or Q4 defective.
b. Proceed to step 6.