The external antenna jack modification :

  A very useful change to make in a Gauss Master is to  make it possible to
have an external antenna input on the meter.  This modification  allows
the addition of a verity of different input devices.  This simple  modification
removes the internal ( yellow ) inductor and installs a jack for external antennae.

First  remove the battery compartment cover and lay it aside. Remove the 4 screws
holding the back on , lay them aside.  look at the back of the gauss master and locate
the  rear of the front panel meter and it's two solder tabs.




Carefully unsolder the two meter tabs with a low wattage iron as to not damage the delicate
meter parts.  Carefully lift up the tabs as seen in the picture above,  they are delicate and
care needs to be taken so they won't break off.

Now  lift up the whole circuit board assembly , taking care not to damage or pull the
two wires ( one red , one black ) that go to the front panel speaker. The jack shown at
 the top of this board with the red and black wires on it , is the  external antenna mod
jack.



When first opened up , a yellow inductor  ( seen below ) will fill the  open notch
seen in the board above.



Carefully unsolder the  two yellow coil pins from the   circuit card ,  do this carefully
taking care not to  over heat the plastic coil bottom and lose either of the pins.
You will want to reuse this coil later on.  Mount a 3.5 mm  jack to the top plastic
of the meter case, directly on and in the opening the coil removal left on the circuit
card.   You will have a jack mounted on the  " right " side as seen from the back and
the " left " side as seen from the front. This is important to have room for the easy
installation  of the jack and leave room on the other side for the audio mod seen elsewhere.



Solder the jack to the circuit card as shown below, the black wire is on the ground
pad of the circuit card and the red wire is soldered to the " hot " pad. This pad is
capacitor coupled to the input amplifier for the VCO / meter circuits.



Check your work carefully .  Gently replace  the card,  and then solder it back in.  Reassemble the
meter  .  This completes the external  antenna / sensor  input mod.