Advanced Instruments 3900, Service Manual

Page: 93 / 184

4CP440 Rev0
(4C35/3905 Service Manual)
Page 5 of 6
Instruction for Head Drive Assembly:
1. Remove the head up/down motor by
removing the two retaining screws and
hardware from the motor mounting plate
(M). Disconnect the sensor board cable
connector and remove the motor.
2. Remove the anti-rotation block and flag
from the assembly after loosening the
setscrew that secures the block to the shaft
(N). Remove the support bracket and
associated hardware (O).
3. Remove the disk sensor from the mounting
block (two slotted screws) (P).
4. Remove the two slotted screws (Q) that
secure the lower head drive assembly to the
deck, and remove the lower assembly.
5. Remove the head rotation idler gear by
removing the stop nut and bushings (R).
6. Remove the top gear plate to reveal two
slotted screws (S). Remove these screws to
disassemble the remaining components.
7. The top section of the assembly can be
accessed by removing the three slotted
screws (T) from the rotation cap.
NOTE: Lubricating grease
(part # MSC003) is also required
on the surface areas (top and
bottom) of the rotation mount that
makes contact with the deck and
the rotation cap.
To reassemble lower section:
8. Stack all components (disk against bearing
housing, head rotation gear, gear spacer)
and secure with 2 slotted screws. Use
Loctite #242 or equivalent on threads prior
to assembly.
NOTE: While assembling the
components, all holes must align
perfectly or the assembly is incorrect.
9. Push the plate switch (U) over the pins and
press until firmly seated against the gear
spacer.
T
P
U
S
R
Q
O
N
M