Modifications to these detectors is an ongoing and evolving process, it involves searching for newer and better components to replace the existing ones for a performance boost. It takes many hundreds of hours trolling documentation, obtaining sample devices and the testing of the upgrades both on the test bench in the Lab and also out in the field. To do the correct field tests involves me traveling for 3 hours to the Gold-fields and carrying out comparison tests against a stock standard detector. A lot of work goes into the testing of even a simple modification.

I am currently working on the GP series to greatly improve the detector output of 5 and 15 volt to 10 and 30 volts. This requires a rebuild of the detectors internal power supplies and a complete upgrade of most components in the detector output stage. This has been done before as when the SD-2000 design was being trialled by the "Seven Apostles" (more on that later) some units were 12 volt units and some were being run on 24 volts. The information that I have received from some of the initial tests were that the 24 volt versions were and still are considered the deepest detectors ever made.

Imagine if this could be instilled into a GP detector design, the depth and sensitivity would be mind boggling.

The Seven Apostles were the group of testers that ran around testing the initial detectors that were developed, they were even installed in other detector cases to make them look like a VLF detector to the untrained eye.

At the time the SD-2000 came out I was running an electronics business in Ballarat in Victoria and when I first saw the depth of these new machines I was awe struck, I was selling Minelabs range of detectors in Ballarat and was obtaining them Wholesale from Ken who ran Finders prospecting supplies in Dunolly Victoria. I was thinking of putting up some interesting stories but I may get sued..lol

Ask Ken how and why he lost his Minelab dealership.  In my opinion Ken was served the rough end of the Pineapple.


Here is a mod for the SD-2000, this will upstage a GP-3000 for depth and sensitivity.

A few of these detectors are getting around with extra frequencies installed for better performance on different sized targets. Like 1 Mhz for large and deep and 3.2 Mhz for smaller Gold. The other day I was talking to a mate and he made mention of upping the detector to run at a 4 Mhz timebase frequency.  Well! FM and I do not mean frequency modulation! This detector is as good as a GP-3000 and then some. By the way its dead quiet.

1st  Change the transmit Fet Gate resistors to around 5 ohms.

2nd Short out the Source resistors on the transmit Fets.

3rd Replace the coil blocking Diode with a 3 amp soft recovery type.

4th Get rid of the blue Earth wire to the case and connect a 10 ohm metal film resistor from the black coil plug wire to the front panel.

5th Countersink all the plate mounting screws for good electrical connection.

6th add another 4.7 nf across the 3 filter caps near the blue trimmers.

7th Retune the pots to null the Earth Field, near the trimmers there are 3 sets of test points, short out either 2 of the 3 and by wiggling a mono coil trim the pot to reduce the warble sound from the Earths magnetic field. Do this on all trim pots.

8th Add variable gain pots to the integrator stages. locate 2 X 220K ohm resistors on the trimpot part of the board and replace with 500K pots. This will give you adjustable gain on both channels.