Test equipment and power supplies · E36 series family

Agilent E3620A: troubleshooting and error codes

The ServiceForge knowledge base holds 32 documented symptoms for the Agilent E3620A, with 65 ranked causes, 36 diagnostic checks with test points and expected values, and 0 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

V2 preregulator control circuit fault (at 10V)

V2 output voltage control circuit not functioning correctly when set to 10V ±1V

Ranked causes

1. U1 or Q3 defective (high voltage at U4 pin 1) (occasional)
2. U4 defective (occasional)
3. U6 defective (occasional)
4. U7 defective (occasional)
5. U5 defective (occasional)

First check

Measure voltage at pin 1 of U4

Test point: U4 pin 1
Expected: Low voltage (0 V) indicates normal; high voltage (+0.7 V) indicates U1 or Q3 defective

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

V2 preregulator control circuit fault (at 19V)

V2 output voltage control circuit not functioning correctly when set to 19V ±1V

Ranked causes

1. U2 or Q4 defective (high voltage at U4 pin 7) (occasional)
2. U4 defective (occasional)
3. U6 defective (occasional)
4. U7 defective (occasional)
5. U5 defective (occasional)

First check

Measure voltage at pin 7 of U4

Test point: U4 pin 7
Expected: Low voltage (0 V) indicates normal; high voltage (+0.7 V) indicates U2 or Q4 defective

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

Low output voltage (V1 supply)

V1 output voltage below the rated minimum value

Ranked causes

1. Q1 open (common)
2. Q6 shorted (occasional)
3. U10A defective (occasional)
4. U10B defective or shorted CR14, CR15 or R48, C9 (occasional)

First check

Attempt to turn on Q1 by disconnecting emitter of Q10

Test point: Q10 emitter
Expected: Output voltage should increase if Q1 can be turned on

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

Low output voltage (V2 supply)

V2 output voltage below the rated minimum value

Ranked causes

1. Q1 open (common)
2. Q6 shorted (occasional)
3. U10A defective (occasional)
4. U10B defective or CR14, CR15, R48, C9 shorted or leaky (occasional)

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

High output voltage (V1 supply)

V1 output voltage exceeds the rated maximum value

Ranked causes

1. Q1 shorted (common)
2. Open CR8 or R48 or defective U10B (occasional)
3. Q6 defective (occasional)

First check

Attempt to turn off Q2 by shorting emitter-to-collector of Q10

Test point: Q2 emitter-to-collector
Expected: Output voltage should decrease if Q2 can be turned off

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 (V2 supply)

V2 output voltage exceeds the rated maximum value

Ranked causes

1. Q1 shorted (common)
2. Open CR8 or R48 or defective U10B (occasional)
3. Q6 defective (occasional)

First check

Attempt to turn off Q1 by shorting emitter-to-collector of Q6

Test point: Q6 emitter-to-collector
Expected: Output voltage should decrease

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

High ripple on output

Excessive voltage ripple observed on supply output

Ranked causes

1. Ground loop in operating setup (common)
2. Main rectifiers open (occasional)
3. Supply operating in current limit mode (occasional)

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

Oscillation or poor transient response

Output exhibits ringing, oscillation, or slow recovery following load changes

Ranked causes

1. Open C13 or C35 (high frequency oscillation) (occasional)
2. Defective output capacitor (occasional)
3. Open C34 or C12 (current limit mode oscillation) (occasional)

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

V1 preregulator control circuit fault

V1 output voltage control circuit not functioning correctly at 16V setting

Ranked causes

1. U18B defective (when pin 7 voltage near +11.3V) (occasional)
2. U3 or Q5 defective (occasional)
3. Open Q9 or R6 (occasional)

First check

Measure voltage at pin 7 of U18

Test point: U18 pin 7
Expected: -12V

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

-12V bias voltage out of spec

The -12V bias supply voltage is not within normal range (±5%)

Ranked causes

1. U14 or U20 open (for high voltage) (occasional)
2. U14 or U20 shorted (for low voltage) (occasional)

First check

Measure -12V bias voltage

Test point: -12V supply
Expected: -12V ± 5%, ±5%

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

-5V reference voltage out of spec

The -5V reference supply voltage is not within normal range (±2%)

Ranked causes

1. U12 or U21 open (for high voltage) (occasional)
2. U12 or U21 shorted (for low voltage) (occasional)

First check

Measure -5V reference voltage

Test point: -5V reference
Expected: -5V ± 2%, ±2%

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

+12V bias voltage out of spec

The +12V bias supply voltage is not within normal range (±5%)

Ranked causes

1. U13 or U23 shorted (for high voltage) (occasional)
2. U13 or U23 open (for low voltage) (occasional)

First check

Measure +12V bias voltage

Test point: +12V supply
Expected: +12V ± 5%, ±5%

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

+5V reference voltage out of spec

The +5V reference supply voltage is not within normal range (±2%)

Ranked causes

1. U11 or U22 open (for high voltage) (occasional)
2. U11 or U22 shorted (for low voltage) (occasional)

First check

Measure +5V reference voltage

Test point: +5V reference
Expected: +5V ± 2%, ±2%

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

Current limit circuit verification required caution

Verify current limit functions and supplies minimum rated current when output is shorted

Ranked causes

1. Current limit circuit malfunction or drift (unknown)
2. Short circuit protection circuit failure (unknown)

First check

Measure current with shorted output at maximum voltage

Test point: Across current sampling resistor RS
Expected: Minimum 1.05 A (1 A + 5%), +5%
Tools: DVM, current sampling resistor

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

Excessive heat caution

Power supply generates abnormally high temperatures during operation

Ranked causes

1. Preregulator control circuit fault (common)
2. Q3, Q4, or Q5 shorted (occasional)

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

Overload condition detected during load operation caution

OVERLOAD LED illuminates during V1 or V2 operation when load current exceeds preset current limit (minimum 1 A + 5%)

Ranked causes

1. Load current exceeds preset current limit setting (common)
2. Short circuit or near-short load impedance (occasional)

First check

Monitor OVERLOAD LED during load operation

Test point: OVERLOAD LED indicator
Expected: OVERLOAD LED OFF during normal operation with load current below 1.0 A + 5% limit

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

Poor load and line regulation

Output voltage varies excessively with changes in load or input line voltage

Ranked causes

1. Bias or reference voltage out of spec (common)
2. Main rectifiers or filters open (occasional)

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

Zero output voltage on V1 or V2

Supply output is at zero volts and does not respond to adjustment

Ranked causes

1. AC line fuse blown (common)
2. Bias or reference voltage out of spec (occasional)

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

Ammeter accuracy check required

Front panel ammeter reading must match calculated current from sampling resistor voltage drop within tolerance

Ranked causes

1. Front panel ammeter calibration drift (unknown)

First check

Measure voltage drop across current sampling resistor RS

Test point: Across RS in series with load
Expected: Current 0.993 to 1.007 A (±0.5% + 2 counts), ±(0.5% + 2 counts)
Tools: DVM, current sampling resistor (100 mΩ per Table A-1)

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

Common mode current measurement

Measure AC common mode current between output and chassis ground at V1 supply

Ranked causes

1. Common mode current circuit evaluation (not a failure symptom) (unknown)

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

Excessive noise or regulation degradation with pulse load

Peak current during pulse-type loading exceeds current limit, causing supply crossover from constant-voltage to current-limit mode and performance degradation

Ranked causes

1. Peak current in pulse load exceeds preset current limit (occasional)

First check

Measure peak output current during pulse load operation

Test point: Output terminals with pulse load applied
Expected: Peak current remains below 1.0 A + 5% during pulse duration; average current below limit

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

Line regulation check required high voltage

Verify output voltage stability when AC input varies from -10% to +10% of nominal line voltage

Ranked causes

1. Line regulation circuit drift or transformer coupling degradation (unknown)

First check

Set low line input (-10% nominal) and record output voltage

Test point: V1 output terminals
Expected: 25.0 V at low line
Tools: Variable autotransformer, electronic load, DVM

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

Load delivers reverse current to supply during operation caution

Active load connected to supply pumps current back into supply during portion of its operating cycle, risking loss of voltage regulation and damage to output capacitor

Ranked causes

1. Active load circuit topology returns current to supply (occasional)

First check

Monitor output voltage during active load operation

Test point: V1 or V2 output voltage
Expected: Output voltage stable and regulated at set value throughout active load cycle; no voltage dips or transients

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

Load regulation check required

Verify output voltage stability when load changes from maximum current to no load (open circuit)

Ranked causes

1. Load regulation circuit drift or component degradation (unknown)

First check

Record output voltage at full load (1.000 A)

Test point: V1 output terminals
Expected: 25.0 V
Tools: Electronic load (constant current mode), DVM

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

Open fuse high voltage

AC line fuse F1 is open or blown

Ranked causes

1. Transient or fatigue-induced failure (common)

First check

Visually inspect fuse F1

Test point: F1 in power inlet
Expected: Filament intact and not discolored

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

Output voltage clamped

Output voltage does not respond to adjustment or remains fixed at a clamped level

Ranked causes

1. Preregulator control circuit fault (unknown)

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

Output voltage higher or lower than rating

Supply output voltage deviates from nominal rating

Ranked causes

1. Bias or reference voltage out of spec (common)

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

Peak-to-peak ripple and noise measurement

Verify peak-to-peak noise on output is within specification using oscilloscope in AC mode

Ranked causes

1. Output filter degradation or high-frequency noise injection in supply (unknown)

First check

Measure peak-to-peak noise on V1 output at 25 V with oscilloscope AC mode, 20 MHz BW

Test point: V1 +/- terminals
Expected: Less than 1.5 mV peak-to-peak
Tools: Oscilloscope (20 MHz bandwidth), AC coupling

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

Reverse voltage applied across output terminals high voltage

External voltage source or load connected with reverse polarity, threatening output capacitors and series regulator transistors

Ranked causes

1. Load or external source connected with reversed output polarity (rare)

First check

Inspect output terminal connections for correct polarity

Test point: V1 +/- terminals and V2 +/- terminals
Expected: Load connected +V to +V terminal, -V to -V terminal; no reverse connections

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

RMS ripple and noise measurement

Verify RMS noise voltage on output is within specification using true RMS voltmeter

Ranked causes

1. Output filter degradation or noise injection in supply circuit (unknown)

First check

Measure RMS noise voltage on V1 output at 25 V

Test point: V1 +/- terminals
Expected: Less than 0.35 mV RMS
Tools: True RMS voltmeter, bandwidth 20 Hz to 20 MHz

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

Voltmeter accuracy check required

Front panel voltmeter reading must match external DVM measurement within specified tolerance

Ranked causes

1. Front panel voltmeter calibration drift (unknown)

First check

Measure output voltage with external DVM at 17 V setting

Test point: V1 +/- terminals
Expected: 16.90 to 17.10 V, ±(0.5% + 2 counts)
Tools: DVM

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

Will not current limit

Supply does not enter current limiting mode when output current exceeds limit

Ranked causes

1. Open OR-gate diodes or defective current limit amplifiers (unknown)

1 corrective action and part numbers 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.