16
TUNING - CRITICAL!!
Before your unit was shipped from the factory, it was tuned to the gamma reading shown on the map for your area. The
factory adjusted gamma setting is written on a tag connected to the outside of the Diver Mag 1. Check the map for the
expected approximate gamma reading in your present area and compare it to what is written on the tag. This is a
preliminary setting, see note at bottom of page.
The tuning of the mag is very broad. Once tuned for the gamma reading in your area, it will operate over a very wide
area (+/- 1,500 gamma). Do not change the factory set tuning (before you test the unit) unless the factory set tuning is
not correct for your area (off by 1,000 gamma or more compared to the map). If it is not properly tuned the readout will
“jump around”.
Note: on land, even a properly tuned fish will not provide a steady readout if it is in an electrically noisy area
or if steel/iron is close to the head.
The Diver Mag 1 is tuned by a switch on the amplifier board which is located in the electronics housing in the rear of
the fish. The amplifier board, microprocessor board, and control panel are all bolted together. To gain access to the
amplifier board, the control panel must be pulled out from the rear of the electronics housing.
To remove the Control Panel:
1. Remove the vent bolt (9/16’ wrench) from the rear of the electronics housing. Removal of this bolt is
essential to prevent a vacuum from being formed when removing the control panel (air pressure may also
be required to help with removal).
2. While firmly holding the Diver Mag 1, pull the knob (located in the center of the faceplate) straight out of
the housing. Note that wires extend from the control panel to other items in the electronics housing; be
careful not to pull the control panel out too far. If you are unable to pull out the control panel, a small
amount of air (from a bicycle pump) can be added to the electronics housing. The pressure plug, that is
included with the spare parts, is screwed into the vent bolt hole, and a small amount of air pressure is
added.
To tune the fish to your area:
3. Refer to the large world map that came with your system and determine the approximate normal gamma
reading in your area (ie: Miami, Florida is 47,500 gammas).
4. Locate the 10 position tuning switch and jumper (J1) on the preamp board, and using the chart on the next
page tune the preamp board by turning on (1) or off (0) each of the 10 switches and setting jumper (J1) on
or off. The switch is on when the lever down towards the board. Take care not to damage the board. This is
a preliminary setting, see note below
5. When reassembling the control panel, be sure the control panel is rotated so the readout is at the top.
DO NOT FORGET IT INSTALL THE VENT BOLT (be sure the o-ring is in place on the vent bolt and tighten
until the o-ring is compressed (do not overtighten).
To check out the new tuning position, see Diver Mag 1 Operation on page 13. If the readout jumps around 5 digits or
more, refer to the chart on the next page and select first the next higher and then the next lower gamma reading.
Change the tuning according, looking for the most stable digital readout.
NOTE:
Once the readout is steady (when operating in the field - see page 13), compare the reading to the reading you
set the tuning switches for. If the actual reading is different by more that 500 gammas, then change the tuning to match
the readout displayed (the map is almost never precisely correct).
DIVER MAG 1
ELECTRONICS HOUSING - REAR VIEW
VENT BOLT
BATTERY CHARGER/
EXTERNAL BATTERY JACK
DIVER MAG 1
CONTROL PANEL
LOW BATT.
LEAK
DIVER MAG 1
AUDIO ADJUST
EAR
CYCLE TIME
OFF
5
10
2
SENSITIVITY
1
10
20
5
KNOB
(FOR FACEPLATE REMOVAL)
