Error Message:

HEAD: checksum error in <head subsystem> calibration block

Applies to:

• Thermal

Service Information:

A checksum was detected in the [head|hdm|hdp|servo_stat] nvs calibration block in the head. Every time a new value is written to the head, the appropriate checksum is calculated and written to nvs.

This error is only reported when the head is initialized (ie. MPE power up).

Note that this error is also generated when new head firmware is loaded.

Check to make sure that all values are present and reasonable in the [head|hdm|hdp|servo_stat] blocks. If not they may still be stored in the MPE copy and can be restored with a "head nvs load" command.

To clear this error, you must type "nvs save [head|hdm|hdp|servo_stat] cal".

After upgrading the head firmware from version 1.38 or earlier to version 1.56 or greater, this error may appear for the servo_stat or 20 Watt calibration block ONLY. If this is the case, and you are unable to clear it by doing an nvs save, then it is safe to disregard the error. It is due to a head/MPE incompatibility, and will not affect functionality or plot quality in any way.

Operator Action:

Call service.

Cause:

• Faulty head NVS battery.
• New head firmware loaded that has new NVS parameters defined.
• Noisy 5 Volt line to the head.

See Also:

• Command: nvs save
• Command: nvs load