Agilent Technologies 6012B Service Manual page 39

SYMPTOMS
CV overshoots
Output noise ( < 1KHz)
Output noise ( > 1KHz)
CV regulation, transient response,
programming time
CC regulation
CV oscillates with capacitive loads
CC oscillates with inductive loads
+15V on A2 Control Board . Voltage regulator A2U11 regulates the voltage across resistor A2R99 to be 1.25Vdc. That
sets the current through zener diode A2VR3 at 7.5mAdc. The output voltage is 1.25Vdc plus 11.7Vdc across A2VR3 plus
the voltage across A2R100.
Circuit Included. + 15Vdc bias supply circuitry from connector pin A2J5-5 through test point A2J7-2 on A2 control board.
Setup . The Main Troubleshooting Setup, page 33. Apply the ac mains voltage to the isolation transformer, and set the
external supply to 0Vdc.
Input:
NODE (+ ) NODE ( - )
A2C52(+) A2C52(-)
Outputs:
NODE ( + ) N0DE ( - )
A2J7-2 A2U11 (ADJ)
A2J7-2 A2VR3 (Anode)
A2J7-2 A2VR2 (Anode)
A2C50 ( + ) A2C50 ( - )
To check if load on + 15V is shorted, remove jumper A2W1 .
-15V on A2 Control Board . Voltage regulator A2U12 regulates the voltage across resistor A2R103 to be 1.25Vdc.
Circuit Included. -15Vdc bias supply circuitry from connector pin A2J5-6 through test point A2J7-21 on A2 control
board.
Setup . The Main Troubleshooting Setup, page 33. Apply the ac mains voltage to the isolation transformer, and set the
external supply to 0Vdc.
Table 3 5. Performance Failure Symptoms (continued)
DEFECTIVE
BOARD
A2
A2, A1
A1, A4
A2, A1
A2
A2
A2
MEASUREMENT
≈ 27Vdc
CHECK FUNCTIONAL CIRCUITS
A2U5A, A2CR19, A2R62
CV Circuit, Input Filter
Transformer A1 T2, output Filter, snubbers A4R1
to A4R11, A4R13 to A4R19, A4C1 to A4C4,
A4CR1 to A4CR4
Wrong sensing (paragraph 3-40), low ac mains
voltage, CV Circuit
Low ac mains voltage, CC circuit
A2R61, A2R60, A2R58, A2R59, A2C33, A2R64,
A2R68, A2C36, A2C37, A2U5, A2R65
A2R61, A2R60, A2R58, A2R57, A2C33, A2R19,
A2C11, A2R58, A2C12, A2U4, A2R35, A2C20,
A2R37, A2C17, A2R29, A2C18, A2R31
SOURCE
A1U4 ,AlC15 (+)
A1U4,A1C17 (+) (6011A)
MEASUREMENT
1.25Vdc
12.9Vdc
6.2Vdc
13.8Vdc
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