9.5 Blower Control
Live voltage is present on the control terminals
of the switches and dials on the front of the blow-
er panel. Avoid touching these controls when
reaching into the control panel and making any
adjustments.
Blower Speed Control - The blower speed control is accessed
from the rear of the control panel by removing the thumbscrew
on the exterior top and screw located at the bottom front of the
control panel. Swing the control panel door open. The blower
speed is adjusted by turning the screw on the variable resistor
mounted on the circuit board adjacent to the controller. (Refer
to Figure 9-1) Turning the screw clockwise increases air veloci-
ty; counterclockwise decreases it.
The blower speed is factory-set and should only be changed
by a qualified technician.
Measuring Blower Motor Voltage - Both blower motor volt-
age and line voltage are measured at the three terminal connec-
tors at the top of the circuit board. Refer to Figure 4-5.
9.6 Receptacle Fuses
Receptacle Fuses (7 Amp - Models 1284/1285, 3 Amp -
Models 1286/1287) - The receptacle fuses (2), located directly
below the blower motor/lights Reset button, are for the recepta-
cles only. If an overload occurs, the fuses will open and require
replacement.
Note: • Turn the power off.
• Unplug the unit.
• Replace the fuses -
P/N 230182, 7 Amp, ¼” x 1¼”
P/N 230166, 3 Amp, ¼” x 1¼”
(Two spare fuses are located in a bracket on
the inside of the control panel.)
Class II, A2 Biological Safety Cabinets_______________________________________________________Routine Maintenance
9 - 3
9.7 Ultraviolet Switch Adjustment Procedure
This procedure must be performed by qualified service per-
sonnel only.
Check UV interlock switch adjustment by fully closing the win-
dow and slowly raising. The UV light should turn off at a win-
dow gap no greater than 3/8”. If adjustment is required, locate
bracket with two screws on the right side light housing. Loosen
these screws approximately one turn. Adjust the window gap to
3/8”. While observing the UV light, adjust the bracket up or
down until the lamp just turns off. Note: UV light does not illu-
minate instantaneously. Tighten screws and verify correct
operation.
These lamps lose their effectiveness over a period of time and
should be replaced when intensity drops below the optimum
level (approximately every six months).
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