Test equipment DC power supplies

Agilent 66332A: troubleshooting and error codes

The ServiceForge knowledge base holds 24 documented symptoms for the Agilent 66332A, with 40 ranked causes, 49 diagnostic checks with test points and expected values, and 22 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Power-on self-test failure (ERR annunciator) high voltage

ERR annunciator illuminates during power-on self-test sequence; output not disabled; allows troubleshooting attempts

Ranked causes

1. Checksum failure in ROM (Read-only, Config, Cal, State or RST) (common)
2. RAM test failure (common)
3. 12-bit or 8-bit DAC test failure (common)
4. Digital I/O test failure (occasional)
5. RS-232 communication error (input overrun, framing, parity) (occasional)
6. Front Panel communication or firmware error (occasional)

First check

Query self-test error code via SCPI command *TST?

Test point: SCPI interface or display
Expected: Error code returned: E1–E5 for ROM failures, E10 for RAM, E11–E15 for DAC, E80 for I/O, E213–E223 for comm
Tools: SCPI interface, display

1 more check with pass and fail actions, 6 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Current limit not functioning caution

Unit does not limit current to programmed value; current exceeds set limit

Ranked causes

1. Current control circuit failure (common)
2. Current monitor amplifier malfunction (occasional)
3. Current sense resistor out of specification (occasional)

First check

Verify CC_Prog voltage setting

Test point: R360
Expected: -4.8V
Tools: Digital voltmeter

1 more check with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

High output voltage caution

DC power supply output voltage higher than expected setting

Ranked causes

1. CV (Constant Voltage) annunciator active (common)
2. Voltage monitor reading incorrect (occasional)
3. Output voltage exceeds safe threshold (occasional)

First check

Verify CV annunciator status

Test point: CV annunciator indicator
Expected: CV annunciator state observed
Tools: Visual inspection

4 more checks with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

No output voltage from power supply caution

Unit operates but produces no output voltage across load terminals

Ranked causes

1. Turn-on control circuit failure (common)
2. Voltage control circuit failure (common)
3. Output stage short or no drive (occasional)

First check

Verify no external short across output

Test point: output terminals
Expected: no short circuit
Tools: Digital voltmeter

1 more check with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit startup abnormal or does not respond to commands caution

Unit display does not come on, protect annunciator stays on, or error message appears during startup

Ranked causes

1. No +5V bias to front panel (common)
2. Front Panel/Display board failure (common)
3. Interface board failure (occasional)

First check

Verify +5V bias supply to display

Test point: A3J2-8
Expected: +5V
Tools: Digital voltmeter

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

OUT OF RANGE message or error code 402 during calibration

Display shows 'OUT OF RANGE' or error code 402 occurs over GPIB when entering calibration mode

Ranked causes

1. Incorrect calibration password entered (common)
2. Forgotten calibration password (occasional)

First check

Enter calibration password

Test point: Front panel or GPIB calibration command
Expected: Calibration mode enabled without 'OUT OF RANGE' message

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Overvoltage detected at unit turn-on high voltage

Unit triggers overvoltage protection immediately upon startup or during power-on sequence

Ranked causes

1. Output stage failure causing overvoltage (common)
2. OV detection circuit malfunction (occasional)

First check

Observe output voltage at turn-on with scope

Test point: output terminals
Expected: no pulse >supply rating
Tools: oscilloscope

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Overvoltage protection not engaging high voltage

Unit does not trigger overvoltage protection when programmed OV setpoint is exceeded

Ranked causes

1. OV detection circuit malfunction (common)
2. OV SCR or gate drive circuit failure (occasional)

First check

Verify OV program voltage at R350

Test point: R350
Expected: ~+2V
Tools: Digital voltmeter

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

20 mA range current readback accuracy out of specification at 0A

Current readback in 20 mA range does not match actual current within limits at 0A

Ranked causes

1. 20 mA range readback circuit calibration drift (unknown)

First check

Measure current with DMM in current mode at 0V output

Test point: DMM in series with output
Expected: Reading should be approximately 0 mA

1 more check with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

20 mA range current readback accuracy out of specification at 20 mA

Current readback in 20 mA range does not match actual current within limits at 20 mA

Ranked causes

1. 20 mA range readback circuit calibration drift (unknown)

First check

Program output voltage to 20V at full-scale current

Test point: UUT output
Expected: 20V applied

1 more check with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

CAL DENIED message or error code 401 during calibration

Display shows 'CAL DENIED' or error code 401 occurs over GPIB when attempting calibration

Ranked causes

1. Inhibit Calibration switch S201 set on A2 Interface board (common)

First check

Verify Inhibit Calibration switch setting on S201

Test point: S201 Switch 3 and Switch 4
Expected: Switch 3 Off, Switch 4 Off for Normal; Switch 3 On, Switch 4 Off for Inhibit Calibration

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Post-repair initialization and calibration

When A2 Interface Board is replaced, supply must be initialized first, then calibrated

Ranked causes

1. A2 Interface Board replacement (common)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Post-repair voltage and current monitoring

Annual recalibration or after replacement of voltage/current monitor amplifier, high bandwidth current amplifier, or current monitor resistors R403/R473 on A1 Control Board

Ranked causes

1. Component replacement in voltage/current monitor circuits (common)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

CC load effect out of specification

Change in output current between full-scale voltage and short circuit exceeds limit

Ranked causes

1. Output current regulation circuit degradation (unknown)

First check

Program supply to full-scale current and maximum programmable voltage

Test point: UUT front panel
Expected: Current set to full-scale, voltage to maximum

3 more checks with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

CC source effect out of specification high voltage

Change in output current when AC line voltage varies from minimum to maximum exceeds limit

Ranked causes

1. Power supply line regulation or feedback circuit degradation (unknown)

First check

Connect AC power through variable voltage transformer set to nominal voltage

Test point: AC power input
Expected: Nominal line voltage applied

4 more checks with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

Current programming accuracy out of specification at 0 amps

Current readback does not match programmed 0 amps value within limits

Ranked causes

1. Current monitoring circuit calibration drift (unknown)

First check

Measure voltage drop across current monitoring resistor at 0A

Test point: Current monitoring resistor
Expected: Voltage drop when divided by resistor value equals programmed 0 amps within specification limits

1 more check with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

Current programming accuracy out of specification at full-scale

Current readback does not match programmed full-scale value within limits

Ranked causes

1. Current monitoring circuit calibration drift (unknown)

First check

Measure voltage drop across current monitoring resistor at full-scale current

Test point: Current monitoring resistor
Expected: Voltage drop when divided by resistor value equals full-scale programmed current within specification limits

1 more check with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

Current sink operation not within specification

Negative current readback does not match actual sunk current within limits

Ranked causes

1. Current sink mode or readback circuit malfunction (unknown)

First check

Measure external power supply and configure for current sink test

Test point: External DC power supply
Expected: 5 V output with current limit set 20% above UUT full-scale rating

2 more checks with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

Fuse status indication incorrect but fuse is good caution

FS protection annunciator displayed but internal fuse is not blown

Ranked causes

1. FUSE signal measurement error (common)

First check

Check FUSE signal voltage at U305B-7

Test point: U305B-7
Expected: ~+2.8V with 20V output
Tools: Digital voltmeter

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Output noise and ripple (PARD) exceeds specification

Periodic and random deviations (ripple and noise) on dc output measured as peak-to-peak or RMS voltage exceed limits; may indicate filter or output stage problem.

Ranked causes

1. Output filter degradation, LC resonance, or switching noise coupling (unknown)

First check

Measure output noise peak-to-peak on oscilloscope

Test point: (+) and (-) output terminals
Expected: Within peak-to-peak limit per performance test record chart CV NOISE (PARD)
Tools: Oscilloscope with 20 MHz bandwidth limit, RF probe tip

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Output voltage changes with AC line voltage variation

Voltage shift measured between minimum and maximum line voltage within rated range exceeds specification; may indicate power supply ripple or regulation issue.

Ranked causes

1. Inadequate input regulation or filter capacitor degradation (unknown)

First check

Measure output voltage at minimum line voltage

Test point: +S and -S terminals
Expected: Per performance test record chart
Tools: Digital voltmeter, variable voltage transformer

1 more check with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Output voltage changes with load current variation

Voltage shift measured between full-load and no-load conditions exceeds specification; may indicate regulation circuit problem.

Ranked causes

1. Poor load regulation or sensing circuit failure (unknown)

First check

Measure output voltage at full-scale load

Test point: +S and -S terminals
Expected: Per performance test record chart
Tools: Digital voltmeter

1 more check with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Transient recovery time out of specification

Output voltage does not return to specified value within specified time following 50% load current change

Ranked causes

1. Load transient generator not properly configured (unknown)

First check

Verify oscilloscope waveform matches Figure 2-2

Test point: +S and -S terminals
Expected: Waveform similar to Figure 2-2 with loading and unloading transients

1 more check with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Voltage programming readback inaccuracy

Front panel display or GPIB readback voltage does not match expected values at zero or full-scale settings; CV annunciator behavior may indicate mode issues.

Ranked causes

1. Calibration drift or readback circuit malfunction (unknown)

First check

Measure output voltage at zero volts setting

Test point: +S and -S terminals
Expected: Within limits per performance test record chart CV PROGRAMMING @ 0 VOLTS
Tools: Digital voltmeter

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Error codes

Code	Meaning	Trigger	Severity
`401`	Inhibit Calibration switch is set	Calibration attempted over GPIB when S201 Inhibit Calibration setting is active	error
`402`	Incorrect calibration password	Wrong password entered over GPIB when entering calibration mode	error
`E1`	Checksum error in Read-only Non-volatile ROM	Power-on self-test	error
`E10`	RAM test failed	Power-on self-test	error
`E11`	12-bit DAC test failed (channel A and B at 0 input)	Power-on self-test	error
`E12`	12-bit DAC test failed (channel A full scale, B zero)	Power-on self-test	error
`E13`	12-bit DAC test failed (channel A zero, B full scale)	Power-on self-test	error
`E14`	12-bit DAC test failed (both channels full scale)	Power-on self-test	error
`E15`	8-bit DAC test failed	Power-on self-test	error
`E2`	Checksum error in Config Non-volatile ROM	Power-on self-test	error
`E213`	RS-232 input buffer overrun	RS-232 serial communication during operation	warning
`E216`	RS-232 framing error	RS-232 serial communication	warning
`E217`	RS-232 parity error	RS-232 serial communication	warning
`E218`	RS-232 UART input overrun	RS-232 serial communication	warning
`E220`	Front Panel communication UART input overrun	Front Panel communication during operation	warning
`E221`	Front Panel communication UART framing error	Front Panel communication	warning
`E222`	Front Panel communication UART parity error	Front Panel communication	warning
`E223`	Front Panel firmware input buffer overrun	Front Panel firmware operation	warning
`E3`	Checksum error in Cal Non-volatile ROM	Power-on self-test	error
`E4`	Checksum error in State Non-volatile ROM	Power-on self-test	error
`E5`	Checksum error in RST Non-volatile ROM	Power-on self-test	error
`E80`	Digital I/O test failed (SEC_PCLR line test)	Power-on self-test	error

Likely causes and actions for each code are in ServiceForge. Connect ServiceForge to your AI

Community

0 fixes logged by technicians through their AI, with outcomes, for this model.

ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.