Advanced Instruments 3900, Service Manual

Page: 40 / 184

NOTE
The flag must remain centered in
both sensors after adjustment.
Check adjustment with the head in
the uppermost position (green
LED) and downmost position (red
LED).
6. Tighten the cap screws to secure the board
in place.
7. Reconnect the head up/down motor to the
main harness.
8. Run the head up/down test from the test
menu to verify proper operation. Operate
one full cassette in the tube transport test as
a final check.
9. Reconnect the back cover fan and install
the back cover on the instrument.
Tube Gripper
See 4C3446 Tube Gripper replacement
instruction.
NOTE While making this adjustment, make
sure that the stir wire is maintained
with the probe alignment.
1. Loosen all of the hex set screws located on
the head casting.
2. Check to see if there is any up/down play
between the tube gripper and the mandrel.
3. If there is play, move the mandrel down
to adjust out any play. Make sure that the
mandrel is not positioned too far down,
as it will cause the end of the gripper to
spread out.
40
10. Tighten the three slotted screws to lock the
well into position.
11. Reposition the V-block and V-block
bracket so that the locating pin in the
sample head nests at the bottom of the “V”
with the sample head fully down. Tighten
the screws and then check the position by
cycling the head.
12. Reattach the back cover to the instrument.
NOTE
The back cover should not remain
off for extended periods of time (>
1 hour) while samples are being
tested. Excessive heat buildup
inside the unit will occur
Head Up/Down Sensor Board
1. Remove the back cover screws. Disconnect
the fan and remove the back cover from
the instrument.
2. Manually rotate the head so that it is
positioned directly over a sample tube
located in position one in a cassette.
3. Disconnect the head up/down motor from
the main harness. This will allow free
up/down movement of the head assembly.
CAUTION
Prevent the operating head
from decending completely to
the deck, or sample probe
damage may occur.
4. While looking into the back of the
instrument at the head up/down sensor
board, move the head to the uppermost
position and note that the green LED is
activated when the flag enters the sensor.
5. While moving the head to the lowest
position (all the way down into the test
well), note that the red LED is activated. If
not, adjust the sensor board by loosening
the two socket cap screws on the sensor
PCB bracket and moving the board just
beyond the point where the red LED turns
on.
The Advanced ® Model 3900 Service Manual