MXT non-pro: any way to retrofit ground grab button?

[Wayfarer]

I have been using my new (to me) MXT non-pro the last few weeks and absolutely love it. Since I usually dig all non-ferrous signals anyway and never hunt at night, I don't care about not having the 7 tones or the backlight. But the one feature of the Pro that I wish my detector had though is the ground grab button. Is there any way to retrofit a small button on the front of the plastic display pod to act as a ground grab button? Installing the physical button is easy, where to wire it into is the difficult part. Without schematics, it makes it hard to figure out. Ideally, there'd be two points on the board somewhere where a simple button could be soldered into. If that isn't possible, maybe there's a way to solder the button circuit into the toggle switch to make it think it has been flipped to the "Ground" position for however long the button is pushed.

Has anybody ever done this? Any ideas?

 

[vito]

Like your idea and have to think about...

 

[vito]

Yup, this can be done by adding a push button switch. you have to solder the two normally open pins to the TRAC switch (gray & black). Bad thing is you have to put two wires through the sealing into the pod. You may reseal it with some silicone (acid free). Not easy but can be done.
The mini SPDT 3-Amp Momentary Pushbutton Switch (Model: 275-1549) from radio shack would be the first advice here.
Only thing is while pushing the button you have to pump the coil a few times like you do on balancing.
Hope this will do it for you.

 

[Wayfarer]

Hey vito, thanks! This is really cool. There might be a way after all! The installation as you describe shouldn't be too hard. There are even two open pins on the switch ready to go!

One question though: this doesn't work exactly like the MXT Pro grab button in that you need to bob the coil with the button pressed? Because with the Pro ground grab, all you have to do is push it momentarily while sweeping the coil. On the non-pro all you need to do is flip the toggle momentarily to "Ground" without having to bob the coil, since supposedly the ground analysis engine is working constantly in the background and it just needs to be transferred to the active GB setting with the momentary button push. So if you still need to bob the coil then this retrofit method works a little differently than the full Pro ground grab?

 

[Aarong81]

Momentarily switching from 'lock' to 'ground' then back to 'lock' again updates the GB instantly since the MXT is always tracking the ground phase. The only problem I can think of is that the wires on the trac 'LOCK' switch will still be active, or in the closed circuit position the whole time that you are attempting to switch to trac 'ground', kind of like trying to be in 'ground' and 'lock' at the same time. You may need a momentary switch that serves two purposes at the same time, one purpose would be to open the circuit I just mentioned(the ground LOCK) and the other purpose is to close the desired trac 'GROUND' circuit. The switch that vito suggested should be able to do this if it has both normally open and a normally closed circuits AND if the MXT trac GROUND and LOCK feature share a common wire such as a ground. The switch only has 3 contacts and I believe the center contact is the common wire used both when the switch is pressed or depressed. You cannot simply force a 'ground' function while the factory switch is in 'lock' so the modded switch needs to do both things at once.

 

[vito]

Hello, this schematic cut out will show that there is no problem to do this with a simple push button switch. But I like the one I mentioned cause it has defined work points.
And yes, the tracking system works all the time, so a push will be enough to set up the new ground volume.
[attachment 301105 MXT-TRACswitch.JPG]

 

[vito]

Sorry Aaron and wayfarer, had a little stress this morning. It's correct to be safe. So I did this little drawing that will do it.
Even if you're in salt and the push button is pressed it will not shorten voltages.

The drawing shows for the "Ground" grab. If you want to "Salt" grab (whatever it is good for?) you only have to change "gray" and "red".
(the positions of ground and salt will not correspond with the MXT face plate)

[attachment 301146 MXT-PushButtonExtension.jpg]

 

[Aarong81]

Vito, is the black common wire used in the center of the original trac switch? If so, and since there are three positions/modes of the trac switch, Which wires are in a closed circuit at which times? I assume red+black=SALT and black+grey=GROUND, so LOCK is all circuits open? Or is there a third combination that achieves LOCK? EDIT: I see your first schematic image which answers what I just asked but I'd still like to have the schematics.......

Where did you find the schematics for the MXT? If you have the schematics, could you post a good image of it? I know it exists because I found a post about adding a backlight to an MXT and he posted this picture but it's the closest I've found online...

 

[Monte]

I felt it wouldn't hurt to add a few copmments here. Naturally personal 'comments' are just personal 'opinion' and in this case are based on ample in-the-field experience.

One question though: this doesn't work exactly like the MXT Pro grab button in that you need to bob the coil with the button pressed?

For best automated Ground Balance the coil should be bobbed over a clean, metal-free spot of ground.

Because with the Pro ground grab, all you have to do is push it momentarily while sweeping the coil.

You CAN, but while the MXT circuitry is reading the ground mineral during search coil sweeps, it is also reading any metal targets or ground irregularities on those sweeps. It is best to locate a bare spot w/o metal and do a quick bobbing of the search coil from about 6" down to ½"/1", and it only takes 1 to 5 brisk bobs and it is adjusted.

On the non-pro all you need to do is flip the toggle momentarily to "Ground" without having to bob the coil, since supposedly the ground analysis engine is working constantly in the background and it just needs to be transferred to the active GB setting with the momentary button push. So if you still need to bob the coil then this retrofit method works a little differently than the full Pro ground grab?

Yes, again, you can toggle to Ground or Salt, whichever is needed, then back to Lock while sweeping the search coil, just like pressing the Ground Grab touchpad on the MXT All-Pro while sweeping the coil, but for the best automated GB setting, with either the standard MXT or MXT Pro/MXT All-Pro, you ought to do a brisk bobbing of the coil over bare ground for an accurate GB update.

Personally, I like the Ground Grab touchpad a lot, but I also have use for the other changes and additions they made to the MXT All-Pro over the original MXT. But while the GG touchpad is quick and handy, it really isn't such a big deal to toggle the stock MXT should you prefer to hunt in 'Lock' and just update as needed. One also, the Ground Grab touchpad, as I mentioned, will update the GB setting for either the Ground [size=small](normal)[/size] adjustment range or for the Salt range. I wouldn't go to the trouble to tinker with the MXT and add a pushbutton that only worked on one GB setting, or to mess with it in any form. That's just me, of course.

Monte

 

[Wayfarer]

Wow, thanks everyone for all the great information. It's amazing the wealth of knowledge out there available literally at our fingertips and the generosity to share that knowledge within the metal detecting community!

So the bottom line is that it can be done, and done relatively simply. As it rains today in windy and cold Boise, I'm reminded that detecting season is quickly coming to an end here. But on the flip side, winter is the height of the researching and tinkering season! I'm going to look into this more carefully as well as really think over whether to do the mod ... Monte your comments got me to thinking maybe I should leave well enough alone, and I see where you are coming from on that. Maybe I'll just stick with what I've got and buy an MXT Pro if I still can't live without the ground grab. But then again, this is a straightforward mod (thanks again Aaron and Vito!) and my compulsion to tinker might get the best of me.

I'm with you Aaron, that it'd be nice to find complete schematics. It make modding easy and sure would help if repairs are ever needed. I'm also a ham radio guy and we couldn't imagine not having schematics for all our radios, so it's a bit of a surprise that detector schematics are so hard to come by. Anyway ...

Thanks again guys for the valuable information. Regardless of whether I go ahead with the mod, it's good that it's now out there in this thread for all to see, as I'm sure there are pothers that would be very interested in this good information.

 

[Wayfarer]

Monte's comments sunk in and I have to agree with him that I'd rather not mess with a great detector So what did I do? I bought a new MXT All-Pro today from my local dealer! (My MXT non-pro is now for sale on the classifieds). The ground grab is something I really wanted since I like to hunt in loc-trac and obsessively update the ground balance every few minutes. I'm just glad that after a not-so-great experience with two V3i's and a VX3 (which was better, but still not my cup of tea), that I finally came 'round to the MXT. The MXT is just an awesome detector that performs great and gives me that White's analog-type audio that I've loved for decades (and lost with the V-series).

Thanks again for the great info on how-to mod the original MXT non-pro wit a ground grab button. I'm sure there are many people who would be very interested in this information. I would be too, had I not decided to make the jump and set myself up with a brand new MXT Pro. This forum is full of great fellow detectorists with the spirit of sharing and helping each other out.