39
Table 3 5. Performance Failure Symptoms (continued)
SYMPTOMS DEFECTIVE
BOARD
CHECK FUNCTIONAL CIRCUITS
CV overshoots A2 A2U5A, A2CR19, A2R62
Output noise ( < 1KHz) A2, A1 CV Circuit, Input Filter
Output noise ( > 1KHz) A1, A4 Transformer A1 T2, output Filter, snubbers A4R1
to A4R11, A4R13 to A4R1 9, A4C1 to A4C4,
A4CR1 to A4CR4
CV regulation, transient response,
programming time
A2, A1 Wrong sensing (paragraph 3-40), low ac mains
voltage, CV Circuit
CC regulation A2 Low ac mains voltage, CC circuit
CV oscillates with capacitive loads A2 A2R61, A2R60, A2R58, A2R59, A2C33, A2R64,
A2R68, A2C36, A2C37, A2U 5, A2R65
CC oscillates with inductive loads A2 A2R61, A2R60, A2R58, A2R57, A2C33, A2R19,
A2C11, A2R58, A2C12, A2U4, A2R35, A2C20,
A2R37, A2C17, A2R29, A2C18, A2R31
+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 ( - ) MEASUREMENT SOURCE
A2C52(+) A2C52(-) ≈ 27Vdc A1U4 ,AlC15 (+)
A1U4,A1C17 (+) (6011A)
Outputs:
NODE ( + ) N0DE ( - ) M EASUREMENT
A2J7-2 A2U11 (ADJ) 1.25Vdc
A2J7-2 A2VR3 (Anode) 12.9Vdc
A2J7-2 A2VR2 (Anode) 6.2Vdc
A2C50 ( + ) A2C50 ( - ) 13.8Vdc
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.