Bandido II μMAX question ~ replacing / cleaning GB pot ~

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Hey folks!

I recently picked up another nice looking Bandido II μMAX in working shape. Having some issues with a dirty ground balance pot, and wondering if there's enough room behind the faceplate to swap a Bourns 10 turn pot, into the original GB pot's place. Ten turn pots are a bit deeper than the original 3-3/4 turn pots (which BTW, are also Bourns 50kΩ).

Have any of you tried a 10 turn GB on THIS model Tesoro? Looks like it may fit. If it does, it'll be close and the knob will need to be a bit higher than stock (no biggie).

If not, have any of you been successful in cleaning the original pots used by Tesoro? Looks like it's intended to be replaced, not repaired.

Thanks!

 

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SUCCESS...!!

Well... I was on a mission to make it work. The 10 turn pot is not only much longer than the original, but also a bit bigger in diameter. Behind the GB pot are two small capacitors which were in the way, and since the pot is bigger around, it interfered with the post for the faceplate screw, and the side of the μMAX housing. Thankfully, there's plenty of plastic on these pots, and I have a Dremel that I like to play with... It took plenty of trial fittings to notch the pot so that it cleared the 2 caps behind it, and a notch for the screw post, and a flat on the side to clear the housing... Also shortened the shaft a bit so the knob didn't stick out too far. Finally got the faceplate with new pot mounted to clear, and put it back together.

It works so nicely with a 10 turn, it's amazing! Ground balance is now smooth and seems to adjust within a half turn, instead of a slight touch of the knob like it was before... SWEET!
I wouldn't have tried this mod if the factory pot was still in good shape. That pot adjusted a bit, then would suddenly jump to a much more negative setting with just a slight touch...not good, and I had to run it a bit positive or way negative... With this 10 turn, I should be able to run it exactly where I want. ^_^

Here's a pic of the "massaging" it took to make the new 10 turn pot fit in the stock position. I should be able to give this modded Bandido II μMAX a full testing this weekend. I'll post an update with the results.

 

[Gone Detectin]

Very cool! Thanks for the info. I was just the other day thinking about doing this and now that I've seen it done, I'll pass lol.

 

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Very cool! Thanks for the info. I was just the other day thinking about doing this and now that I've seen it done, I'll pass lol.

Yeah; my other Bandido II μMAX still has a good GB pot, so I probably won't be jumping to swap that one out. Just had a wild hair yesterday and wanted to see if it could be done, as I already had some 50K 10 turn pots for Cibola mods (no pot massaging there). This was not a simple swap and solder, but it should work very nicely. If I have any problems (shouldn't) I can always put the stock (bad) pot back in, and pay the $50 to have Tesoro look at it. The detector itself wasn't altered, just that new pot I used. ^_^

BTW, if anyone is feeling the need for a 10 turn GB pot of they're own... They're a Bourns 3590S-2-503L, and can be had for around $3 each on eBay. Don't bother with the suppliers who want more for 'em, and no need to get the more expensive 3540S Bourns pot; specs are nearly identical, and the 3590S pot is plenty durable for a metal detector. Not all Tesoros can use the 10 turn in their original spot, due to the size of the 10 turn; on my BIIμMAX, you can see it really did not fit... Using this to add an external GB adjustment to the Cibola, this pot is put where the pinpoint button was. No idea about other Tesoros.

After all this, I do not recommend that anyone modify or alter their Tesoro detector. You may just render it useless, and need to send it to Tesoro hoping they can fix it, and it'll probably be out of your own pocket.

I just felt a little nuttier than usual yesterday... ^_^

Here's a pic of it buttoned back up. The knob is about 3/32" higher than before, but it looks factory original with the 10 turn in there.

 

[Gone Detectin]

But really though thanks for posting this. I was just on the cusp of doing this mod and had just noticed the 10 turn pots (which have not been to easy to find) for sale on ebay. At 3$ each I ordered 2 and was wondering if they were the real deal (from china) as most of these 10 turns I saw last year were on the bay for 10$+.. Was thinking about the mod back then.

Now that I know what it takes.. I'll wait if I can. And again, thanks for the post.. saved me some time.

And it looks nice and clean too.

 

[pinenut]

But really though thanks for posting this. I was just on the cusp of doing this mod and had just noticed the 10 turn pots (which have not been to easy to find) for sale on ebay. At 3$ each I ordered 2 and was wondering if they were the real deal (from china) as most of these 10 turns I saw last year were on the bay for 10$+.. Was thinking about the mod back then.

Now that I know what it takes.. I'll wait if I can. And again, thanks for the post.. saved me some time.

And it looks nice and clean too.

If you have the patience and a steady Dremel hand, you will make it fit. It does take several test fittings, and the ground away areas on the pot can be made to look prettier. I saw no reason to pretty it up; just wanted it to fit and function smoothly, as it's never seen from the outside anyway. If you do try "massaging" one of these to fit the BIIμMAX, grind slowly when making your clearance notches. There's about 1/8" of plastic before you grind into the resistor wire in the back, and about 3/32" thick plastic on the sides. Easy to wreck the pot if you're not careful; I deliberately destroyed one by grinding in to see how far I could go (they're only $3..).

The pots originally recommended in the write-up for adding external GB on Cibola are the more expensive Bourns 3540. Those pots are a little more durable than these cheaper ones, but not needed for a metal detector. Both #s are genuine Bourns 5OK Ohm 10 turn precision pots, just different grades of 'em. Bourns probably offers a 10 turn 50k in at least 5 different grades, from inexpensive consumer type, to (expensive) ball bearing high-end military and scientific. Tesoro actually used this less costly grade as factory original. These cheaper 3590 pots should last the life of our detectors, and if not, just replace with another $3 pot. ^_^

Hoping to have a little time for a thorough testing sometime tomorrow. I just did a quick GB to check it out late last night, after putting it back together.

Good luck and happy hunting!

 

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It's so awesome..!

..Had the 10 turn GB modded Bandido II microMAX out for a couple hours today. It was so smooth in trash, I couldn't believe it! With the 10 turn, I could "power balance" it right to the very edge in disc mode... so it just gave a slightly negative, single chirp when quickly lifting the coil straight up, but was still silent on the swing. The 10 turn makes it SO much easier to fine tune, it's amazing.
I'm very happy with the way this pot works...so happy, I'm tempted to open up my Outlaw to see if there's enough room for a 10 turn pot in it... ^_^

Making that pot fit isn't for the timid and it took a while to do...but man, does it work nicely!

 

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a little update on the 10 turn GB Bandido...

...Still working great!

Been using it as often as possible lately, but with the holidays, family and weather distractions, not much time for detecting so far this year. Got to play yesterday for a couple hours at an old camp where I'd found a few things last summer. 10 turn Bandido in hand with the little coil...dug up another pocket knife and a brass, '50s vintage makeup 💄 case. Using this modded BIIμMAX is really a pleasure in trashy spots.
I quite like these 10 turn pots for ease of perfectly setting your GB right to the stable edge. I plan on adding these to a few other Tesoros when I can.



...a bit of yesterday's junk. ↑


Here's the pot I used, in case anyone is thinking about a 10 turn GB: