The Minelab F1A4 mine detector is one of the finest detectors Minelab ever made! With our modifications, these detectors become very capable gold finders.

We worked with Jack Lange, who was the owner of Goldhunter Detectors, to develop and implement the Level 1 and Level 2 modifications for the ex-military F1A4 mine detectors. Jack still uses one of our F1A4 Level 3 detectors to this day!

The initial aim of the level 3 modifications was to free you from all of the unique parts used on the F1A4 such as the handle and shaft and the D cell battery carrier. When these parts fail, you can no longer buy them.

The end result was more than amazing!

We came up with a sturdy aluminum bracket to allow the control box to be mounted to a normal Minelab GPX type shaft.

You can also use the standard GPX handle with the ground balance button as we only use the GPX type ground balance plug on any detectors we modify.

The power plug is replaced for the standard 4 pin plug used on the SD and GP type detectors and all necessary internal modifications are also performed for this to work properly. We recommend using an adjustable battery system that allows you to set the voltage from 6v up to 8.4v to get the best on ground performance.

The coil socket is fitted with a standard 5 pin type plug, gold plated pins, with the nut on the outside. These plugs are specially machined to fit the F1A4. If you see an F1A4 with this type plug, it was most likely done by us.

Gain control.

The Level 3 gain control was specifically designed for the F1A4. The gain control allows the detector to be adjusted for ground and emi conditions, whichever is worse. By adjusting the gain for the ground you are working you maximize the detectors ability to detect gold missed by others. Our gain control comes with a mark to show where the factory gain is. When you know this, you will detect with confidence!

Frequency control.

The Level 3 is fitted with a high quality rotary switch for the frequency control allowing 5 different frequencies to be selected. Just like gold and coils come in all different shapes and sizes, the frequency control allows the detector to be optimized for the coil you have fitted. There are 2 frequencies lower than standard for larger coils, standard frequency, and 2 frequencies higher than standard allowing the detector to be set incrementally to its highest sensitivity.

Timing Control.

The Level 3 is fitted with a rotary switch for timing control. This allows 4 timings to be chosen from. There are 2 timings for non mineralised ground and 2 sensitive timings for mineralised ground. With the 2 sensitive timings, most times you can work ground that GPX's find difficult and can find gold that has been missed.

Channel switch.

The Level 3 is fitted with a channel select switch which allows each of the channels to be heard individually just like the rest of the SD series of detectors. This can allow you to get a better idea about a target before digging. In severe ground select ch1 using std or fine timing and most ground noise and hotrocks are ignored, gain can be increased and the detector is still very sensitive unlike the SD series.

The level 3 is also fitted with our threshold, tone and volume controls. We perform many internal upgrades that enhance the performance of the F1A4.


If there are minor repairs required we do these as part of the modifications. We know these detectors inside out.


©2019 by Detectronics Australia.