Unable to do a stroke cal: Laser Problems

• Is the laser disabled?
• Is the laser turning on?

Is the laser disabled?

* Stroke cal and write laser disabled from the TH2 head
* Stroke cal and write laser disabled from the MCE
* Stroke cal and write laser disabled from the MPE
* How to check if the write laser is enabled or disabled for the head or host
* How to disable/enable the write laser

Stroke cal and write laser disabled from the TH2 head

When the write laser is disabled and a stroke cal is issued from the head, the message “command success” is displayed immediately. This can indicate that the laser is disabled.

TH2 > stroke cal
*** Command Success ***

Stroke cal and write laser disabled from the MCE

When a stroke cal is issued from the MCE (and the write laser is disabled) the message “command success” is displayed immediately, as well as a message indicating that the laser is turned off. The laser is disabled and the stroke cal failed.

QUANTUM>> stroke cal
S MPC: Stroke Balance: Start of stroke balance
S MPC: Head media found, using HDM 1
S MPC: Write laser disabled, skipping stroke balance
S MPC: Stroke Balance: End of stroke balance
*** Command Complete
S MPC: Elapsed time = 0.023 seconds
C MPC: Write laser is off


Stroke cal and write laser disabled from the MPE

When the stroke cal is issued from the MPE (and the write laser is disabled) you will see a message stating that the the host is waiting for the head to stabilize the beam, then you will see a message indicating that the laser is on and the command was successful. This behaviour is very similar to an actual stroke cal, but because the laser was disabled the stroke cal failed.

>> stroke cal
Waiting for beam balance sensor to stabilize ...
Calibrating stroke for media 1 ...
Light setpoint: 32767
Light peak error: 32767
WARNING: laser is on
*** State message: Stroke command (13) Complete (4068254)


How to check if the write laser is enabled or disabled for the head or host

The write laser can be disabled both on the head and the Host (MCE, MPE, ICE)

• TH2 Head: To determine if the write laser is enabled on the head: true means enabled, false means disabled.
  TH2 > set sys laserenable
  

  Key	Sub.	Parameter	Active	Default	Units
  ------	------	-----------	------	------	------
  [03507]	SYS	laserenable	True	True

• Host (MCE,MPE): To determine if the write laser is enabled on the host: value=0 means disabled, value=1 means enabled.
  QUANTUM>> set head wenable
NVS head (Exposure Head) subsystem:
wr_laser_enable = 0 Saved = 0 Default = 1
Range: 0 to 1

  >> set head wenable
NVS head (Exposure Head) subsystem:
Head data loaded, active values match head saved values
wr_laser_enable = 1 MPE Saved = 1 Default = 1
Range: 0 to 1

How to disable/enable the write laser

• From the head:

  Laser Action	Head Commands	Notes
  To disable the write laser	TH2 > eng TH2 > set sys laserenable false	Note that if the laser is disabled on the head side, after a reset the host will change to write laser disabled, therefore it is always a good idea to check both the head and the host for write laser enable, particualrly after a reset.
  To enable the write laser	TH2 > eng TH2 > set sys laserenable true	n/a

• From the host:

  Laser Action	Host Commands	Notes
  To disable the write laser	QUANTUM>> set head wenable 0 NVS head (Exposure Head) subsystem: wr_laser_enable = 0 Saved = 0 Default = 1	The commands are the same for both MCE and MPE.
  To enable the write laser	QUANTUM>> set head wenable 1 NVS head (Exposure Head) subsystem: wr_laser_enable = 1 Saved = 0 Default = 1	The commands are the same for both MCE and MPE.

Is the laser turning on?

One way to start troubleshooting stroke cal problems is to turn on the laser, which can be done from either the host or the head. Do this initially with verbose turned off, but if any problems arise, turn verbose on to obtain more details.

TH2 > laser on
The laser power has been calibrated!
*** Command Success ***

laser on fails

Check the resulting error message and, if required, turn verbose on for BPD and LDD. Check for the following error conditions:

• Laser too cold ? (should have link to error)
• Laser too hot (should have link to error)
• Laser safety switch on (should have link to error)
• Not enough current for the power (should have link to error)
• bpd errors (should have link to error)

laser on is successful

Continue testing stroke cal. Turn the laser off and enable verbosity for the four subsystems involved in a stroke cal.

QUANTUM>> redirect enable
*** Command Complete
TH2 > eng
*** Command Success ***
TH2 > vbs enable bpd 7
*** Command Success ***
TH2 > vbs enable ldd 7
*** Command Success ***
TH2 > vbs enable lvd 7
*** Command Success ***
TH2 > vbs enable bbs 7
*** Command Success ***


Once this is complete, initiate another stroke cal. With the verbosity set this high, large amounts of information will be produced. Also see the Sample Results.

TH2 > stroke cal
The laser power has been calibrated!