Advanced Instruments 3900, Service Manual

Page: 82 / 184

4CP190 Rev1
(4C35/3905 Service Manual)
Page 2 of 3
6. Remove the pump head:
a. Unscrew the four screws (C) securing
the cover plate (D) and pull the pump
head away from the body.
b. The pump head is made up of two
halves. The front half (E) connects to
the tubing on the right side. The rear
half (F) contains the rubber valve plates
(G). Note the correct orientation of the
rear half to the front half, then separate
and remove the rear half and set aside.
7. Change the diaphragm (H):
a. Grip the diaphragm carefully with both
hands, and turn it counter-clockwise to
unscrew it. Remove the diaphragm
from the pump, taking care not to lose
the small washers.
b. Transfer the small washers from the
threaded stud on the old diaphragm to
the new one, and then screw the new
diaphragm into the pump, firmly by
hand.
c. Press the edge of the new diaphragm
down firmly into place.
8. Change the valve plates (G):
a. Take the rear half of the pump head (set
aside earlier) and remove the old valve
plates.
b. If necessary, clean and dry the valve
plate recesses.
c. Place the new valve plates, clean and
dust-free, in the correct positions in the
rear half of the pump head.
9. Reassemble the pump head:
a. Combine the two halves of the pump
head back together, taking care to
properly orient the rear half to the front
half.
C
D
F
G
H
E
E
F