Test equipment DC power supplies

Agilent 657xA: troubleshooting and error codes

The ServiceForge knowledge base holds 23 documented symptoms for the Agilent 657xA, with 29 ranked causes, 70 diagnostic checks with test points and expected values, and 24 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 supply does not power on or display is blank

Unit fails power-on self-test, output disabled, front panel displays error code or message indefinitely, no GPIB or front panel commands accepted

Ranked causes

1. Front panel RAM test failed (common)
2. Front panel ROM test failed (common)
3. EEPROM checksum error (occasional)

First check

Verify power-on self-test error code displayed

Test point: Front panel display
Expected: Error code E1 to E12, SERIAL TIMOUT, SERIAL DOWN, UART errors, SBUF errors, EE WRITE ERR, or SECONDARY DN

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

Signature analysis testing required

Verification of microprocessor-based circuits using signature analyzer to compare IC pin signatures against known correct values for fault isolation

Ranked causes

1. Incorrect IC signature indicates component fault (common)
2. Open printed circuit track or soldering problem (occasional)
3. Short circuit at output node loads (occasional)

First check

Confirm power supply firmware revision

Test point: Front Panel ROM (AlU3) or Secondary microprocessor (A5U504) label, or GPIB *IDN? query
Expected: Revision matches SA table header (e.g. A.01.06 for Primary Interface, A.01.07 for Front Panel, A.01.04 for Secondary)

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

Calibration: EEPROM initialization and factory preset transfer

After replacing front panel board or EEPROM, the power supply must be reinitialized with proper constants and calibrated. New calibration constants must then be transferred to EEPROM factory preset locations.

Ranked causes

1. EEPROM or front panel board replaced (common)
2. Newly initialized and calibrated supply without factory preset constants (common)

First check

Run initialization program from Figure 3-18 with proper model number input

Test point: Program input prompt for model number
Expected: Program accepts valid model (6571A, 6572A, 6573A, 6574A, 6575A, 6671A, 6672A, 6673A, 6674A, 6675A)

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

Calibration: Programming voltage and current parameters high voltage

Setup and verification of programming parameters for Agilent 657xA power supplies using front panel or GPIB controller

Ranked causes

1. Parameter calibration procedure (common)
2. Parameter measurement and verification (common)

First check

Program full-scale voltage for model

Test point: Front panel or GPIB controller
Expected: 6571A/6671A: 8V; 6572A/6672A: 20V; 6573A/6673A: 35V; 6574A/6674A: 60V; 6575A/6675A: 120V

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

Bench series supply GPIB initialization

For Bench series supplies without GPIB board, temporary A2 GPIB board substitution required to perform initialization and factory preset transfer.

Ranked causes

1. Bench series supply lacks GPIB interface for initialization (occasional)

First check

Remove original A2 Isolator board

Test point: A2 board slot on Bench supply
Expected: Isolator board removed without damage

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

Calibration: Bench series initialization with GPIB board

For Bench Series supplies without built-in GPIB, temporarily install A2 GPIB board to enable initialization and factory preset calibration loading.

Ranked causes

1. Bench series supply requires GPIB board for initialization (common)

First check

Install A2 GPIB board

Test point: A2 slot
Expected: GPIB board installed, isolator board removed

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

Calibration: Constant current tests verification

Verify all constant current mode specifications including programming, sink operation, load effect, source effect, and PARD

Ranked causes

1. Power supply requires performance verification after service or initial setup (unknown)

First check

Connect current monitor resistor per Table 2-1 configuration B

Test point: As shown in Figure 2-1B
Expected: Resistor installed with correct accuracy per Table 2-1
Tools: Current monitor resistor per Table 2-1

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

Calibration: Constant voltage tests verification

Verify all constant voltage mode specifications including programming, load effect, source effect, PARD, and transient recovery

Ranked causes

1. Power supply requires performance verification after service or initial setup (unknown)

First check

Connect DVM to +S and -S terminals as specified

Test point: +S and -S
Expected: Meter connected per Figure 2-1
Tools: DVM

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

Calibration: EEPROM initialization

EEPROM AlU6 on A1 Front Panel Board stores GPIB address, model number, and calibration constants. Procedure required when front panel board or EEPROM is replaced.

Ranked causes

1. Front panel board or EEPROM replaced (common)

First check

Run initialization program with selection I

Test point: Program prompt
Expected: Initialization (I) or Factory Preset Replacement (F)?

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

Calibration: Measurement setup verification high voltage

Verification of proper test measurement setup including sense terminal connections, wire gauge, and cable shielding

Ranked causes

1. Test measurement setup configuration (common)

First check

Verify sense terminal connections

Test point: +S, -S, +LS, -LS terminals
Expected: Sense terminals connected to load sense terminals; connections per Figure 2-1
Tools: Visual inspection

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

Calibration: Restore factory constants

Power supply requires factory calibration constants restored; password lost or calibration locked out

Ranked causes

1. Calibration denied or incorrect password (common)

First check

Turn off supply and remove top cover

Test point: Power switch
Expected: Supply powered off

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

Calibration: Transfer constants to factory preset

After initialization and calibration, transfer new calibration constants to EEPROM Factory Preset CAL locations.

Ranked causes

1. New calibration constants require storage in factory preset locations (common)

First check

Run initialization program with selection F

Test point: Program prompt
Expected: Initialization (I) or Factory Preset Replacement (F)?

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

Calibration: Verification test setup

Operation verification and performance tests require specific test equipment and setup procedures to verify power supply operation against specifications.

Ranked causes

1. Operation Verification test required before Performance tests (common)

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

CC load effect out of specification

Output current change between full-load voltage and short circuit exceeds specification

Ranked causes

1. Current regulation poor or feedback network incorrect (unknown)

First check

Measure output current at full-load voltage (CV mode)

Test point: Current monitor resistor
Expected: Full-scale current with CC annunciator on
Tools: DVM, Electronic Load in CV mode

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

CC noise (PARD) excessive

Output current ripple and noise rms amplitude exceeds specification

Ranked causes

1. Current output filter or feedback circuit noise performance degraded (unknown)

First check

Measure baseline noise with power supply off

Test point: Current monitor resistor via rms voltmeter
Expected: Record baseline to subtract from on measurement
Tools: RMS voltmeter, current monitor resistor per Table 2-1

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

Current programming and readback inaccuracy

Measured current or front panel readback does not match specification at low or high current settings

Ranked causes

1. Current sensing circuit or display calibration error (unknown)

First check

Measure voltage across current monitor resistor at 0A

Test point: Current monitor resistor
Expected: Within specified Low Current limits when divided by resistor value
Tools: DVM, current monitor resistor per Table 2-1

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

Current sink (CC-) readback inaccuracy

Current sink display readback does not match specification during negative current operation

Ranked causes

1. Current sink circuit or negative current display calibration error (unknown)

First check

Measure current sink value via monitor resistor

Test point: Current monitor resistor
Expected: Stable reading
Tools: DVM, external test supply, current monitor resistor

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

CV load effect out of specification

Output voltage change between full load and no load exceeds specification

Ranked causes

1. Load regulation poor or output impedance high (unknown)

First check

Record voltage at full-scale load current

Test point: +LS and -LS
Expected: Stable reading with CV annunciator on
Tools: DVM

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

CV noise (PARD) excessive

Output ripple and noise (PARD) peak-to-peak or rms amplitude exceeds specification

Ranked causes

1. Power supply filtering or output stage noise performance degraded (unknown)

First check

Measure output noise amplitude peak-to-peak on oscilloscope

Test point: + and - output terminals
Expected: Within specified PARD Peak-to-Peak limits Hz to 20MHz
Tools: AC-coupled oscilloscope, RF tip probe

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

CV source effect out of specification high voltage

Output voltage change between low-line and high-line AC input exceeds specification

Ranked causes

1. Line voltage regulation poor or AC mains rejection inadequate (unknown)

First check

Measure output voltage at low-line AC input

Test point: +LS and -LS
Expected: Recorded value Vac
Tools: DVM, 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

Serial link signature incorrect

Signature analysis detects fault in serial link between primary and secondary interfaces

Ranked causes

1. A2U109 serial interface IC fault (common)

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

Transient recovery time excessive

Output voltage takes longer than specification to recover within 100mV after 50% load change

Ranked causes

1. Output regulation loop response slow or transient response network incorrect (unknown)

First check

Measure time for voltage to settle within 100mV after load step

Test point: +LS and -LS, trigger on transient slope
Expected: Within 900µs
Tools: Oscilloscope, Electronic Load

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

Voltage programming and readback inaccuracy

Front panel display or GPIB readback voltages do not match specification at low or high voltage settings

Ranked causes

1. Output voltage outside specification limits (unknown)

First check

Measure output voltage at low voltage setting

Test point: +LS and -LS
Expected: Within specified Low Voltage limits

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

Error codes

Code	Meaning	Trigger	Severity
`1`	Calibration denied on Systems Supply GPIB calibration attempt	Attempted GPIB calibration with INHIBIT CAL jumper installed	warning
`2`	Password error; incorrect calibration password entered	Attempted calibration with incorrect password	warning
`CAL DENIED`	Calibration denied; power supply calibration is inhibited	Attempted front panel calibration with INHIBIT CAL jumper installed	warning
`E1`	Front panel RAM test failed	Power-on self-test	critical
`E10`	Secondary interface 5 volt readback test failed	Power-on self-test and *TST?	critical
`E11`	Ambient temperature readback test failed	Power-on self-test and *TST?	warning
`E12`	CV or CC DAC tests failed	Power-on self-test	critical
`E2`	Front panel ROM test failed	Power-on self-test and *TST? query	critical
`E3`	Front panel EEPROM checksum test failed	Power-on self-test and *TST?	critical
`E4`	Primary interface external RAM test failed	Power-on self-test	critical
`E5`	Primary interface internal RAM test failed	Power-on self-test	critical
`E6`	Primary interface ROM test failed	Power-on self-test and *TST?	critical
`E7`	GPIB interface test failed	Power-on self-test	critical
`E8`	Secondary interface RAM test failed	Power-on self-test	critical
`E9`	Secondary interface ROM test failed	Power-on self-test and *TST?	critical
`EE WRITE ERR`	EEPROM write failure	During operation or self-test	error
`SBUF FULL`	Serial buffer failure	During operation or self-test	error
`SBUF OVERRUN`	Serial buffer overrun failure	During operation or self-test	error
`SECONDARY DN`	Serial data line failure on main board	During operation or self-test	error
`SERIAL DOWN`	Serial data line failure	During operation or self-test	error
`SERIAL TIMOUT`	Serial data line failure	During operation or self-test	error
`UART FRAMING`	UART framing error	During operation or self-test	error
`UART OVERRUN`	UART overrun error	During operation or self-test	error
`UART PARITY`	UART parity error	During operation or 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.