Cleaning The Magnet Assembly And Bobbin - A&D GX-A Series Maintenance Manual

5.3 Cleaning the Magnet Assembly and Bobbin

The magnet assembly and the bobbin will require cleaning if the balance has a repeatability
problem. Particles of metal, dust or other foreign material can collect around the bobbin. If
such material touches the bobbin, the bobbin will not move correctly. Metal particles are
attracted to the magnet and tend to stand straight out. The gap for the bobbin is very narrow,
so be very cautious while removing particles.
Note: Do not use compressed air to blow out the magnet well. There may be
particles of magnetic material stuck to the bottom of the magnet.
The tools that you use near the magnet should be free of plating and
non-magnetic. A flake of plating or metal particles will be attracted to
the magnet.
The screws used in this balance are non-magnetic. Do not substitute
screws made of magnetic material.
① Prepare a 5 cm-long adhesive tape for cleaning. Use a paper backed or cloth tape (do not
use a tape that can be torn easily, such as cellophane tape, it may stick to the magnet and
be very difficult to remove).
② Clean around the inner and outer surfaces of the magnet well using the adhesive tape.
③ Clean the inner and outer surfaces of the bobbin using the adhesive tape.
④ Inspect the magnet well and bobbin using a very strong light. Look for any particles stuck
to the surfaces. Metal particles may be shiny or dark. Look for anything sticking out from
the sides of the magnet.
⑤ Reassemble the force motor and test it for repeatability. Corner load error can often be
traced to a repeatability problem.
If there is still a problem, disassemble the force motor and check closely for particles in the
magnet gap.
GX-A/GF-A Maintenance manual
Tape
Yoke unit
Page 25
Tape
Magnet
Shield unit