MAINTENANCE
24
The motor brushes should last for a minimum of 1000 hours of operation.
To renew brushes proceed as follows:
Open the lid and remove the rotor, close the lid, and disconnect the centrifuge
from the power supply.
Turn the centrifuge on to its back Unscrew and remove the two screws securing
the front rubber feet, and the other two screws that locate and secure the
instrument chassis to the base frame. Place corrugated cardboard or other
protection on the upper part of the centrifuge, then withdraw and lay the chassis
on top
Removing The Brushes
Unscrew the brush-retaining cap. The brush is held within a carrier against a
tensator roll spring. If the carrier does not spring free on removal of the cap, a thin,
stiff wire, hooked at one end may be used to assist. Do not use force. Gently
press the arms of the carrier together and withdraw the brush. On withdrawal, note
the position of the roll spring in the carrier in relation to the brush and motor as the
new brush must be fitted in the same manner. It will be seen that a small pin, fitted
near the rear end of the brush locates in a guide slot along one arm of the carrier.
Note that the free end (tongue) of the roll spring is held, near the end of one arm
of the carrier, facing in the direction of fitting.
Fitting New Brushes
Locate the new brush in the carrier with the pin located in the slot and the brush
pushed fully into the carrier against the tension of the roll spring Hold the
assembly together with the roll spring in the same relationship to brush and motor
as when the old brush was removed, and insert the front end into the brush
housing of the motor Take care to ensure that the 'tongue' of the roll spring lies,
facing forward, flat with the carrier (if not, gently press it down with a small
screwdriver) before pushing the assembly home into the brush housing. Note: If
the 'tongue is bent backwards against the carrier upon insertion, it may break off
and the spring will be ineffective Check that the carrier moves freely in and out
against the tension of the spring. Refit the brush-retaining cap and tighten finger-
tight. Replace and secure the instrument chassis and the rubber feet and turn the
centrifuge the right way up. Run the centrifuge with an unloaded rotor on the drive
shaft to a speed of 1000 rev/min for half-an-hour, to bed in the brushes.
6.8 Renewing The Fuse
To renew the fuse: disconnect the centrifuge from the power supply at the mains
plug. Unscrew the fuse holder cap and remove the fuse. Inspect and replace as
necessary with the correct rating. For 220V/240V model, the plug fuse may also
need to be checked. Fit the new fuse and refit the holder back into the receptacle.
If the fuse blows again during use, contact the local distributor, or MSE (UK) Ltd.
NB - If the fuse blows immediately or blows again during normal use, the power
supply should be disconnected and the service engineer called.
