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Ground Balance Issue And (my) Solution With The Tesoro Mojave


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So I have a Tesoro Mojave that I love, it made me put the "all mighty" AT Pro down and never pick it up again. But ever since I got it I couldn't use it on the "Low" ground condition setting because it would false like crazy. I finally decided to have a serious look around and see if anyone had this problem and had fixed it and I couldn't find anything. I posted on treasurenet to see if anyone could help with at least some knowledge of the trim pots on the circuit board but i didn't get much help. Then I remembered about a website I saw a while ago, TreasureLinx, that had some diagrams of Tesoro mods on it. So I emailed Sven, the owner and asked if he could help out. He told me which trim pot controlled the ground balance and I fixed the problem, at least so far I think it's fixed. I'm going to copy and paste the posts I made to treasurenet and the email to Sven here...

 

(POST 1)

Hey all. I've searched around google but I can't really find any information about this. I bought a Mojave on eBay a year or two ago and I love it. I found my first and best gold ring with it and i even ditched my AT Pro in favor of it. The problem is it's always been pretty hot and falsed a lot in the low setting of the GB. In southern CT I had to run it on the high ground balance even though I'm pretty sure the ground there isn't that mineralized. I love in Costa Rica now and the few times I've taken it out it likes to false on the high GB setting and the low is basically unusable.

I've tuned the ground balance on my compadre that ran hot when I got it too but from what I can see there's no GB potentiometer screw on the Mojave. Does anyone know of anything I can do tune it a bit so it doesn't run so hot?

(EMAIL TO SVEN)

Hi, my name is Josh. I have a Tesoro Mojave that runs hot in high ground phase mode and I was wondering if you knew if either of the trim pots on the board are for adjusting the ground balance? I'm trying to ask on treasurenet and on the Facebook Tesoro group but I'm pretty sure it was you who put a manual ground balance on your Mojave.

I've adjusted my compadre because when I got it it would false on some basalt rocks and now it runs perfectly quiet. But the Mojave has been chattery since I got it. Here's a picture of the board, I don't think you need it but I marked the two trim pots and the two wires coming from the ground phase toggle. Thanks!

 

(EMAIL BACK FROM SVEN)

Hi, one towards the PCB center should be GB pot, the other will be disc bias- don't touch it.
Tom has reworked his Mojave with full mods, contact him thru Findmall Link deleted since Findmall Forum update broke all old links
Sven

 

(EXPLANATION OF MY SOLUTION ON TNET)

Ok I fixed this one too (I'm referring to the almost same problem I had with the Compadre that is documented on this forum also). I emailed Sven from treasurelinx, hoping he'd see the email and get back to me at some point in the next couple weeks...it was less than 12 hours before I had a reply. I asked him if he knew which trim pot, if any, controlled the ground balance. He informed me it was the one on the left, the innermost one that did. The one on the outside controls the discrimination and should not be touched. Here's what I did.

I opened up the control box and exposed the board. I made sure the disc was set to the lowest position in iron (basically no disc), the sensitivity was on 4 and the ground condition was on low. I took the coil and pumped it at the ground and it falsed. I then turned the trimmer all the way CLOCKWISE until it wouldn't turn any more. I did this very very easily and lightly. If you attempt this remember, easily and lightly. I then pumped the coil to the ground to make sure it wasn't falseing still and it wasn't. Then I started turning it back COUNTER CLOCKWISE a tiny bit at a time until it started to false and then turned it slightly back CLOCKWISE to where it didn't false any more. Remember, the movements are slight when turning the trimmer. 

I also noticed that when I touched the yellow wire coming from the ground condition toggle, it made the machine false also. Knowing why and being able to fix it is probably beyond my knowledge and comfort zone so I made sure that when I put it back together it was snug and didn't move. I'm guessing some of the falseing was for that wire and other falseing was from the ground balance being off.

Again, this was the solution to my problem. It might not be the same for everyone but it worked for me. I hope this helps at least one person with the same problem since I couldn't find a solution for it myself, or even a good picture of the board

 

Here are some pictures of the Mojave board for reference

IMG_20190514_064525-01.thumb.jpg.f30145e4744597b98f36d97cfc43ba20.jpg

 

840011430.thumb.png.e2b600f11fed87460c45f3195ab076f4.png

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Just curious as to what number your ATpro ground balances at??  Probably just more mineralized soil in your area led to using “high” ground setting.   Mojave is my go to travel machine and depending on location have used both settings.  

Tesoros are great fun in the tweaking and modding department.  I have a coupke frankensteined compadres that are super fun to use in certain applications.  The only problem I see with adjusting the GB on Mojave is giving up the more neutral “low” ground setting.  If you have ground that suits it you will definitely get a bit more depth. But in hotter ground your solution will probably serve you better.  

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Thanks Steve, I've said it before and I'll say it again, I hate looking for solutions for problems and seeing the op say, ok I fixed it, thanks for the help, and there's zero explanation on how it was done. 

 

Noah, I think you may have given me a few pointers before with my compadre when I was having a problem with it falseing on basalt rocks. My AT Pro ground balanced around maybe 80-87 when I was in CT. From what I remember I think that was the preset ground balance for normal non mineralized ground. I'm in Costa Rica now and I don't have that machine any more but I'll see what my equinox balances at in a little bit. I think even from when I got it before I adjusted it, it was still a little off. 

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Touching wires inside I would expect would sound off. My Tejon can pick up my hand when I run it past the coil. They are sensitive machines. 

You could drop the sensitivity down if needed. Does the Mojave have a ground tracking like the Lobo or is it just a generic high or low switch?

The few times I ran my Tejon at the beach I did have to drop sensitivity down to gb it as I got close to the water but was able to nudge it back up to close to full after. This worked fairly well but there were areas I simply couldn't run it at all. The AT Pro I have was much more forgiving in crap soil and beach.

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4 hours ago, DukeBoxer said:

Thanks Steve, I've said it before and I'll say it again, I hate looking for solutions for problems and seeing the op say, ok I fixed it, thanks for the help, and there's zero explanation on how it was done. 

 

Noah, I think you may have given me a few pointers before with my compadre when I was having a problem with it falseing on basalt rocks. My AT Pro ground balanced around maybe 80-87 when I was in CT. From what I remember I think that was the preset ground balance for normal non mineralized ground. I'm in Costa Rica now and I don't have that machine any more but I'll see what my equinox balances at in a little bit. I think even from when I got it before I adjusted it, it was still a little off. 

Probably hot ground down there in CR. Volcanic basalt everywhere I would imagine.  

Thats the fun part of Tesoros or other analog machines for that matter.   Being able to get hands on and adjust things and see how it plays out. 

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At least you can take it apart and fiddle and not worry about the warranty. 

Has anyone out there set up to do repairs on them?

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  • 3 weeks later...

From my observations Tesoro mojave - coil 7 "precizion works on setting GB to" Low "works well on 4 bar - Fe3O4 mineralization, and on setting GB to" High "here he is missing something to stable work - detection at 7 bar BlackSand mineralization ...

My question N1. is - will Tesoro Mojave to set GB - "High" in such a situation ... to -extremely strong mineralization better to work on DD type coil than to its Concentric 7 " Precizion coil?

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