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4.9.4 Reel drum
Each reel drum consists of a three-part injection moulding comprising a drum and rim
moulded in clear translucent plastic and an interrupter flag in black opaque material.
The drum is sandwiched to a diecast hub by a circlip upon which the hub is securely
attached to the motor shaft by a roll pin passing through cross-holes common to the shaft
and hub.
The hole in the motor shaft is not referenced to any specific rotor-index position. It is
therefore necessary to provide a means of aligning the reel index positions to the reel side
frame. This is achieved by slots in the side frame which allow the motor body to be rotated a
few degrees about its axis before being clamped into position by its two fixing screws.
This alignment is set on manufacture and once set should never normally require to be
adjusted, unless the motor is removed from its frame for any reason. However this change
will require specialised equipment to position the motor correctly on the frame.
4.9.5 Motor alignment
Motor to frame alignment can be checked as follows: -
Put the machine into Self-Test mode as described in Sect 2.3.2
The reels will revolve and come to rest with the first reel band symbol positioned on the
payline.
4.9.6 Photo electrics
The MPU6 can instruct the drive electronics to cause either forward or reverse direction of
the reel in discrete steps, but will not know the true position until it receives some feed-back
from the reel.
This takes the form of a marker pulse occurring once per revolution and corresponding to
the first symbol on the reel band aligning with the payline. The marker pulse is achieved by a
flag attached to the reel drum interrupting a beam of light from a LED source to a photocell,
and is referred to as the interrupter flag.
When the machine is first switched on the reels spin at least two revolutions for the MPU6 to
determine the exact reel position and check serviceability.
If the photo circuit is not interrupted during this initialisation an alarm condition is entered,
with the identity of the faulty reel indicated on the machines and MPU6 alphanumeric display.