Product

Machines affected

All devices with a Thermal 2.X head

Error

You may see the following error messages:

• [00216] Beam-balance prevented by the range of pulse heights
• [00218] Beam-balance error exceeds the maximum error

Symptoms

• Poor contrast ratio, particularly because the off-light levels are too high
• When you run BeamBalance.spt, the value for max correction is high (that is, the value is over approximately 175)

Accompanied by:

• Long laser on hours (typically greater than 1000)
• Banding
• Poor stroke profile
• Poor contrast

Cause

After 1000–2000 laser hours, the characteristics of the light valve change and therefore the voltage setting may no longer be valid. Adjusting hvtrim may improve the stroke profile.

Solution

Note: When solving banding problems on a TH2 head, you should first optimize the hvtrim (this drives the light valve). Next, run ContvBP.spt to either confirm that bpd beamposition is 0 or to pick the new beam position value.

1. Reset the value of bpd beamposition to 0.
2. Run ContvHVtrim.spt (contrast vs HVtrim). When the script prompts you for a laser power value:
   • If the customer only uses one media type, use the laser power for that media.
   • If the customer uses more than one media type, pick a laser power value that is an average for the media that they run.
3. Look at the third graph (offvHV) and select the value at the lowest point (the bottom of the curve).
4. Apply the new value using the command
   th2>set lvd hvtrim xx.x
   Note: This is the voltage that drives the light valve.
5. Run ContvBP.spt (contrast vs beam position) to confirm that the beam position with the lowest contrast ratio is 0.
6. Check the media setup (for example, sd, power, slope and curve).

Sample graph: In this example, the value to use is 71 volts.

See also

Thermal 2 Planned Maintenance

Technical contact(s)

Doug Jeffery

Submitted by

Doug Jeffery

Date submitted

16 Jan 2006