Ground Balance Test; Coil Connector Test - Minelab F1A4 Service Manual

F1A4 Field Service Manual – Level 1 and Level 2 Maintenance
4.3

GROUND BALANCE TEST

Note: The F1A4 Control Box will memorise its last Ground Balance settings when
switched off then on again. If a Control Box/Coil combination has been previously
balanced to the GB Test Piece, on re-testing, a response to that hot rock will not be
heard again. The same Control Box/Coil combination must be re-balanced with a
GB Test Piece with different characteristics before re-testing. (If a suitable GB Test
Piece is not available, a piece of ferrite or local ground around the workshop may
suffice.)
The F1A4 should initially detect the GB Test Piece (a change of threshold
tone will be heard) as the GB Test Piece is moved to and from the Coil. The F1A4
will then become "balanced" to it, i.e. the F1A4 threshold will remain stable as the
GB Test Piece is moved to and from the Coil.
1. Release the Off/Search/Balance switch so that it returns to the Search
position.
2. Move the GB Test Piece as described above and confirm that there is no
further response from the F1A4.
3. If a response is still heard check that there is no metal on the technician or
the GB Test Piece and repeat the test. If the F1A4 still responds to the GB
Test Piece, go to Section 5.1.3
4.4

COIL CONNECTOR TEST

Loop the coil cable and anchor against side of the control box, approximately
250mm from the coil connector. Grasp the coil cable 75mm from the coil connector
and gently turn 30 degrees side to side, listening for a change of threshold. If there
is a noticeable threshold change (ie similar in volume to test piece threshold
change), the coil connector is to be reterminated. Go to Section 6 for Coil
Retermination procedure.
While holding the Off/Search/Balance switch in the Balance
position, move the GB Test Piece up and down,
approximately 25 to 100mm from the Coil.
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