PERFORM PREVENTIVE MAINTENANCE CHECKS AND SERVICES
ON THE DENTAL OPERATING UNIT
The A-DEC Dental System consists of two main subsystems. These are the
dental chair and the dental operating unit. The A-DEC chair incorporates electronic
circuitry to provide for control of the hydraulic motor/pump assembly. Two small circuit
boards with cable connections and chair mounted control switches provide for chair
control. The A-DEC dental operating unit utilizes the Century II Automatic Control
System in conjunction with the foot control for handpiece operation. This lesson covers
PMCS procedures on the dental operating unit for which you, as the medical equipment
repairer, are responsible.
OVERVIEW OF SYSTEM DESIGN
Refer to figure 4-1 for a schematic of the flow of water and air throughout the
dental operating unit.
a. Unregulated air and water enter the unit from a floor mounted service box
through the air and water closet valves. Air is supplied through line #1 to the air and
water utility module. Two sources of air are then distinguished at this point; continuous
filtered regulated air and continuous filtered unregulated air.
(1) The filtered unregulated air is supplied to the master control block
through line number 2. Switching the master control toggle ON creates a holdback air source
to control the handpiece hanger valves. It also creates a pilot air source which enables
other functions of the dental operating unit.
(2) From the control block, pilot air, enabled (regulated) by the master
toggle, is supplied to the air and water pre-regulators through line number 3. The air
preregulator accomplishes three tasks.
(a) Air is supplied to the water heater (if so equipped).
(b) Air is then supplied to the pilot air valve (water relay valve) on the
main incoming water line through line number 4. This enables an air actuated diaphragm thus
allowing water to enter the utility module through line number 5.
(c) Pilot air is also supplied to the air regulators and the air and water
utility module through line number 6. This signal is applied to another air actuated diaphragm.
The air pre-regulator is adjusted thus changing the regulated air delivery pressure.