Advanced Detection Systems 1200E Series Installation Manual And Owner's Manual page 32

A brief description of the detector's circuits may be helpful at this time. Refer to the circuit board layout for
the following explanation. The receiver section of the detector consists of two receiver coils. These coils are
connected to the circuit board via the blue coaxial cable plugged into J3. One coil is connected between
ground and TP2, the other is connected between ground and TP4 near the top right of the circuit board. The
output of these coils must be exactly "balanced" for correct operation of the metal detector. The metal
detector does have an automatic balance feature that will maintain this balance after the initial calibration
has been set. The detector is factory balanced by installing resistors and/or capacitors between TP2 and TP7
and/or between TP4 and TP5. Sometimes, due to environmental changes, these values need refining. The
capacitance can be varied somewhat by means of the trimmer and the resistance can be changed by means
of the potentiometer. The main objective is to vary the capacitance and/or resistance in order to regain the
factory balance.
6. Observe the five red "calibration" LED's on the front panel. Think of the calibration LED's as a "bar
graph" type display. The goal is to get the lights as dim as possible. You may also watch the "residual"
reading on screen #3 to achieve the minimum numeric value.
7. Refer to the circuit board layout and locate the trimmer capacitor adjustment (top center, slight right,
marked C1).
8. Adjust the trim capacitor to dim the LED's as much as possible or to get the lowest value on the residual
reading. It is important to be careful when making this adjustment so that the screwdriver does not slip
off of the adjustment and damage the trim capacitor. If this happens, the circuit board will normally need
to be returned to the factory for repair. It is best to use an adjustment tool with a captive type adjuster at
one end. Leave the trim capacitor set at the point where the LED's are at their dimmest.
9. Next, adjust the potentiometer while watching the LED's or the numerical value until the lights are at
their dimmest or the numerical value is at its lowest.
10. Alternately adjust the trim capacitor and the potentiometer to get the LED's as dim as possible. If you
can get the LED's to something less than the first three at full brightness or the numerical value below
500, this should be sufficient. However, try to get the number as low as possible.
11. Un-jumper the jumper at J6 and restart the detector by means of pressing the reset switch, SW1. Store
the J6 jumper on one pin only for future use. The metal detector should go through its self-checking and
should pass the self-balancing test.
NOTES
A. If, during steps 8-10, you are unable to get the LED's to go dimmer or the numerical value to go below
the maximum (approximately 1724), then reduce the field strength to low. This can be done by
navigating to screen 24 and setting the Field Strength to "low". After completing step 10 with the setting
at low, make sure that you go back and reset the field strength to high and complete steps 8-10 again.
B. This balancing procedure will work for all Model 1200 metal detectors. If you have questions, please
give us a call. If you are confident that you are doing the procedure correctly and are still not getting
results, then there is probably something else wrong and either a service technician is required on site or
the detector must be returned to the factory for repair.