Agilent Technologies E3620A Manual De Funcionamiento Y Servicio página 83

STEP ACTION
1 Check +12V bias.
2 Check -12V bias.
3 Check +5V reference.
4 Check -5V reference.
SYMPTOM
High output voltage 1. Attempt to turn off Q2 by
(higher than rating) shorting emitter-to-col-
lector of Q10.
2. Measure voltage at
base of Q10.
Low output voltage 1. Attempt to turn on Q2 by
(lower than rating) disconnecting emitter of
Q10.
2. Attempt to turn off of
Q10 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.
Table A-4. Output Voltage Bias and Reference Voltage Check
RESPONSE
a. Normal (+12V ± 5%)
b. Voltage high
c. Output voltage lower or
higher than rating
a. Normal (-12V ± 5%)
b. Voltage high
c. Voltage low
a. Normal (+5V ± 2%)
b. Voltage high
c. Voltage low
a. Normal (-5V ± 2%)
b. Voltage high
c. Voltage low
Table A-5. V1 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
a. Proceed to step (3).
b. Check U13(for V2 output) or U23(for V1 output) for
short.
c. Check U13(for V2 output) or U23(for V1 output) for
open.
Note: A short within U4, U5, U6, U7, U9, U10, U18 or
U19 can cause low +12V or -12V bias voltages.
a. Proceed to step (4).
b. Check U14(for V2 output) or U20(for V1 output) for
open.
c. Check U14(for V2 output) or U20(for V1 output) for
short.
a. Proceed to V1 supply troubleshooting Table A-5.
b. Check U11(for V2 output) or U22(for V1 output) for
open.
c. Check U11(for V2 output) or U22(for V1 output) for
short.
a. Proceed to V1 supply troubleshooting Table A-5.
b. Check U12(for V2 output) or U21(for V1 output) for
open.
c. Check U12(for V2 output) or U21(for V1 output) for
short .
RESPONSE
volt.
volt.
+0.7V.
-0.7V
A-8
NEXT ACTION
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.