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Turn-On Checkout 56
Checksum Errors.
If the display shows EE CHKSUM, the power supply has detected an EEPROM checksum error. A checksum error can
occur due to the following conditions:
■ Excessive number of write cycles to an EEPROM (see "Nonvolatile Memory Write Cycles" in "Supplemental
Characteristics" tables). This condition, which would appear only after extended use, is not recoverable and requires
service.
■ Loss of ac input power during a checksum calculation. This condition, which is very unlikely, is recoverable.
You may be able to recover from a checksum error by writing to the EEPROM while the power supply is in the calibration
mode. To do this, proceed as follows:
1. Enable the calibration mode by pressing
.
2. PASWD will appear on the display.
3. Press the number keys corresponding to the password, followed by
. The Cal annunciator will go on.
Note On new equipment, the calibration password corresponds to the four-digit model number (such as
). See "Appendix A - Calibration" for more information about the calibration password.
4. Save any operating state (for example, press
).
5. Turn the power off and then back on.
A normal display free of error messages should appear. If not, the power supply requires service.
Runtime Error Messages
Under unusual operating conditions, the VOLT or AMPS display may show +OL or -OL. This indicates that the output
voltage or current is beyond the range of the meter readback circuit. Table 3-4 shows other error messages that may appear
at runtime.
Table 3-4. Runtime Errors
Display Meaning
Display Meaning
EE WRITE ERR
EEPROM status timeout
UART FRAMING
UART byte framing error
SBUB FULL
Message too long for buffer
UART
OVERRUN
Overfilled UART receive buffer
SERIAL DOWN
Failed communication with
front
UART PARITY
UART byte parity error panel
STK OVERFLOW
Front panel stack overflow