BRUEL & KJAER 4220 - Dismantling the Pistonphone

abnormal leakage in the coupler of the Pistonphone can be detected when
calibrating an instrument the linearity of which is ascertained at low fre-
quencies.
Dismantling of the Pistonpb.one.
To take the Pistonphone apart, proceed as follows (see also Fig. 2) :-
(1) Remove the coupler by unscrewing it from the Pistonphone.
(2) Remove the piston retaining spring and take out the pistons.
(3) Unscrew the two set-screws from the body of the Pistonphone.
(4) Unscrew the motor housing from the black motor mounting piece.
(5) Gently push out the pistons.
To reassemble the Pistonphone:-
(1) If necessary, the cam disc and the pistons should be cleaned in a
detergent.
(2) Screw the motor housing onto the motor unit.
(3) If necessary, apply a drop of high quality oil to the cam disc (e.g. Esso
"Univis 40" or Shell "Microtime Type A Ultra Light").
(4) Replace the two set-screws.
(5) Insert the pistons and replace the retaining spring. Fh:~ally replace the
coupler.
Note: The pressure of the retaining spring should be 20 g. approximately.
A too low pressure would cause distortion, and a too high pressure produces
an excessive wear on the piston tips. If it is intended to operate the Piston-
phone at 800 Hz it may be necessary to slightly increase the spring pressure
in order to ensure constant contact of the piston tips on the cam disc, in
spite
of the high rotating speed. However, the spring pressure must be de-
creased again as soon as returning to the normal rotating speed .
Spare springs and pistons can be ordered separately. See the parts list.
Caution: Never touch the pistons while operating.
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