CAL & ADJUST
3-3
Versapulse Select Service Manual
0621-499-01 03/94
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2. Check rod calibration values.
Go to the second service screen and note the cap voltage values displayed for each of the four
channels at minimum (low point) and maximum (high point).
The HVPS maximum output is 1500 VDC, so each rod must be capable of making its
maximum pulse energy (high point) at less than 1500 VDC. Typical values at high point are
from 1280 to the low 1400's. Typical voltages for low point are in the 700 to 900 VDC range.
For Nd:YAG the typical values at high point are from 500 to 800 VDC, and typical low point
values are from 200 to 400 VDC.
As the rod temperature increases (during use), its output will tend to drop off for a given cap
voltage. The software compensates for this effect, so as the rod temperature increases, it is
normal to see the cap charge voltage required at a particular pulse energy increase. Since the
system goes through its autocalibration at turn on, when the rods tend to be cooler, the cap
charge voltages found during autocal will tend to be lower than those that might be required
during sustained, high duty cycle operation. Thus, a channel with a cap charge voltage in the
mid to high 1400's @ 2.8 Joules at turn on may require a cap charge voltage higher than the
HVPS can provide to make 2.8 Joules during operation.
If the system has failed to complete autocalibration or channel performance appears poor, perform
the YAG Channel Adjustments (Topic 3.4).
3. Inspect debris shield and clean/replace as required.
4. Check the power supply voltages, coolant temperature and coolant conductivity.
5. Check the fiber focus using a test fiber.
If the system passes autocalibration and channel performance appears normal (service screen min/
max cap charge values are good), check for proper alignment of the beam into the fiber. This is done
using a special test fiber (0621-675-01). The fiber proximal end is coated with a red ink (Berol 8800
red marker) that records an impression of the YAG beam footprint where it enters the end of the
fiber. The laser is fired into the test fiber, then the fiber end is examined using a hand held 100X
microscope. A good alignment will result in a "concentric" footprint, i.e., the footprint will be
approximately centered in the fiber core and be well away from the cladding that surrounds the fiber.
a.) Install a test fiber in the 100X fiber examination microscope and examine its surface to confirm that
it is unused.
b.) Install the test fiber at the fiber port, then turn on the system and go to service mode.
c.) Turn on all the rods, select 850 cap volts and a pulse rate of 20 Hz.
d.) Fire the laser for approximately one second.
12/95
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