Agilent Technologies AGILENT MODELS 6023A and 6028A service manual Troubleshooting CV Circuit

Troubleshooting CV Circuit

V-MON, the output of CV Monitor Amp A2U7, is 1/4 the voltage between + S and - S. CV Error Amp A2U8 compares V-MON to CV PROGRAM. Innerloop Amp A2U10A stabilizes the CV loop with IVS input from A2U10C. The measurements below verify that the operational amplifier circuits provide expected positive and negative dc voltage excursion when the CV loop is open and the power mesh shut down.

Circuits Included. Constant Voltage (CV) Circuit and buffer amplifier A2U10C.

Setup. The Main Troubleshooting Setup, page 29. Apply the ac mains voltage to the bias transformer, and disconnect the external supply Remove the + S jumper and connect A2J3-2 ( + 15V) to + S. Set MODE switch settings B4, B5 and B6 all to 0. Set VP to 0Vdc by connecting to P or set VP to + 5Vdc by connecting to A2J3-1 according to SETUP below.

Outputs:
NODE ( + )	SETUP	MEASUREMENT
VM		3.75Vdc
A2U10C-8		4.7Vdc
A2U8-6	VP = 0	-14Vdc
A2U10A-1	VP = 0	-14Vdc
A2U8-6	VP = 5	4.7Vdc
A2U10A-1	VP = 5	5.1Vdc

If the failure symptoms include output voltage oscillation, check if the CV Error Amp circuit is at fault by shorting A2U8-6 to A2U8-2. If oscillations stop, the CV Error Amp circuit is probably at fault.

Troubleshooting CC Circuit

I-MON, the output of CC Monitor Amp A2U1, in volts is 1/6 the output current in amperes. CC Error Amp A2U2B compares I-MON to CC PROGRAM. Differentiator circuit A2U3D and A2U3C stabilizes the CC loop. It differentiates IVS and has a voltage gain of 16. Its output is summed with CC PROGRAM at CC Error Amp A2U2B.

The measurements below verify that the operational amplifier circuits provide expected positive and negative do voltage gain when the CC loop is open and the power mesh shut down.

Circuits Included. Constant Current (CC) Circuit on A2 control board.

Setup. The Main Troubleshooting Setup, page 29, except connect the external supply with polarity reversed to the unit's + OUT ( - ) and - OUT ( + ) terminals. Apply the ac mains voltage to the bias transformer. Set the external supply to 3.0Adc constant current with a voltage limit in the range 5 to 20Vdc.Set IP to 0Vdc by connecting to P or set IP to + 5Vdc by connecting to A2J3-1 according to SETUP below.

Outputs:
NODE ( + )	SETUP	MEASUREMENT
IM		0.50Vdc
A2U2B-7	IP = 0	-14Vdc
A2U2B-7	IP = 5	+14Vdc
A2U3D-13	+0.015Vdc
A2U3C-9	+0.015Vdc
A2U3C-8	+0.25Vdc

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