Alignment
6-23
2. Change the pc board.
a. Turn off the Model 3955 electronics module.
b. Remove the two mounting screws, then gently raise the pc board
off the mount. Be careful, there are still three cables connected to
it. Do not lose the five (5) washers.
c Remove the plug from
J
1
, then unscrew and remove the cables
from
J
2
and J
3
. Note which cable goes to which connector. Set the
pc board aside.
d. Install the appropriate pc board by reattaching the cables and
replacing the screws. Refer to Figure 6-16 for the correct place-
ment of cables and washers. Leave the screws loose.
e. Verify the cables to J
2
and J
3
are attached to their respective BNC
connectors on the input bezel (Figure 4-1).
f. Turn on the Model 3955 electronics module.
3. If you have not already done so, loosen the two photodiode pc board
mounting screws and move the board around until a maximum signal
is observed on the PHOTODIODE bar graph on the front of the Model
3955, then tighten the mounting screws. If the LED bar graph is satu-
rated, reduce the pump power to bring the signal below saturation
before aligning the pc board.
This completes the alignment of the photodiode pc board.
Test for Proper Modelocking
This procedure assures good cavity performance and tests whether or not
an alignment of the AOM is necessary.
1. If not already on, turn on the Model 3955 electronics module and push
the STATUS mode locker enable button. The ENABLE LED will light.
If you just turned on the Model 3955, allow about 20 minutes for the
heaters and electronics to reach operating temperature. The two
TEM-
PERATURE
indicators on the laser control panel will turn from red to
green when the heaters stabilize.
A flashing red GTI TEMPERATURE indicator means either (a) the GTI
is not installed or (b) there is a cable problem. Note: a flashing indica-
tor is normal for a fs laser because there is no GTI.
Table 6-4: Photodiode part Numbers
Assembly Part Number Wavelength (λ)
0452-3280 < 900 nm
0452-3250 > 900 nm
Observe proper static electricity control prior to changing the pc board.
Warning!
ESD
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