Agilent Technologies 6571A, Service Manual

Page: 63 / 161

Troubleshooting 63
Post-Repair Calibration
When Required
Calibration is required annually and also whenever certain components are replaced. If components in any of the circuits
listed below are replaced, the supply must be recalibrated.
Note
For calibration procedures, see Appendix A of the Operating Manual.
Location Component
A5 Control Board CV/CC DACs/operational amplifiers, CV/CC control circuit amplifiers, readback
DAC/operational amplifier, readback comparators.
A1 Front Panel Assy A1 Front Panel Board or EEPROM AlU6.
Note: If either of these front panel components is replaced, the power supply must first be
reinitialized before calibration (see "EEPROM Initialization" ) .
Inhibit Calibration Jumper
If CAL DENIED appears on the display when front panel calibration is attempted (or error code 1 occurs when GPIB
calibration is attempted on a Systems Supply), the INHIBIT CAL jumper (see Figure 3-15) is installed. This prevents the
power supply calibration from being changed. To calibrate the power supply first move this jumper from the INHIBIT CAL
position to the NORM position.
Calibration Password
In order to enter the calibration mode, you must use the correct password as described in Appendix A of the Operating
Manual. As shipped from the factory, the supply’s model number (e.g., "6671") is the password. If you use an incorrect
password,
PASSWD ERROR appears on the display during front panel calibration, or error code 2 occurs during GPIB
calibration, and the calibration mode is disabled. If you do not know the password, you can recover the calibration function
by restoring the preset factory calibration constants as described below.
Restoring Factory Calibration Constants
This procedure allows you to recover the factory calibration constants. The ability to do this allows you to operate the
power supply for troubleshooting and/or to recalibrate it as required. To restore the original factory calibration constants,
proceed as follows:
1 Turn off the supply and remove the top cover.
2 Move the jumper in test header J3 on the A1 Front Panel Board from the NORM to the FACTORY PRESET CAL
position (see Figure 3-15).
3 Turn on the power supply and note that ADDR 5 and then PWR ON INIT appear briefly on the front panel display.
4 When PWR ON INIT no longer appears, the supply’s factory calibration constants have been restored and the password
has been changed to 0. There is no longer any password protection. You can now turn off the supply and restore the
calibration jumper to the
NORM
position (see Figure 3-15).
5 Turn on the supply. You may now set a new password (if desired) and recalibrate the power supply.