Ground Balance, Threshold and Sensitivity Settings

[ToddB64]

Hi Folks !

First, let me establish one point and correct me if I'm wrong, but I believe the Tesoro Bandido II microMax metal detector has combo analog-digital circuitry.

The above detector also has control dials to adjust Ground Balance, and Threshold and while there are several other controls on the faceplate, these are the two of my primary interest at this time.

My questions regarding the above detector: Are the GB and Threshold controls "tied-in" and have any affect on each other when adjusted ? Or do they operate independently, with no direct affect (or effect, i.e. resulting affect) on one another when adjusted ?

One other query I would also appreciate an answer on has to do with the Teknetics Gamma 6000 metal detector. I believe this machine can be termed as primarily digital technology and the Threshold level is actually controlled by and in conjunction with the Sensitivity control.

Thanks,
ToddB64

 

[Carl-NC]

The Bandido II uMax is purely analog, no micro at all. It was probably the last of the all-analog Tesoro models. The GB and threshold controls should be fairly independent. It's possible when changing the GB you might hear a slight change in threshold, but threshold has no effect on GB.

The Gamma is mixed analog/digital. All controls are digital. Since it's a silent-search machine there is no audible threshold, but there is still a target threshold. Yes, as you crank up sensitivity the threshold lowers which can make the machine chatter.

 

[Monte]

But I will add that there are some distinct differences in adjustment features between those two detectors, and very pronounced difference in performance afield, if used in a more ferrous-challenged environment.

That's one reason why the Tesoro Bandido II µMAX is in my Regular-Use Detector Outfit. I used to use the Gamma 6000 but preferred the Omega 8000 and they served me well for many common urban Coin Hunting tasks. I just let my last two Omega 8000's go last month, but in my outfit of detectors a Fisher F44 w/7" Concentric coil has filled in that gap. I worked them side-by-side for several months before making the decision to thin the Tek. models.

I have the F44 mainly as a quick-grab for urban Coin producing sites, but mainly as a loaner for friends, family and property owners when I need it to offer and help gain permission.

The Bandido II µMAX is a solid unit that will always be in my Outfit, especially for more challenging sites to join other proven performers.

Monte

 

[ToddB64]

The Bandido II uMax is purely analog, no micro at all. It was probably the last of the all-analog Tesoro models. The GB and threshold controls should be fairly independent. It's possible when changing the GB you might hear a slight change in threshold, but threshold has no effect on GB.

The Gamma is mixed analog/digital. All controls are digital. Since it's a silent-search machine there is no audible threshold, but there is still a target threshold. Yes, as you crank up sensitivity the threshold lowers which can make the machine chatter.

Carl-NC,

Thanks much for your concise and straight-forward answers !

While we are discussing the Tesoro Bandido 2 Micromax, I would like to in some way verify that my previously-owned machine's circuitry is operating correctly. I assume Vince Gifford is busy trying to finish up and fulfill standing commitments to customers regarding any (a) machines that were returned previously under Warranty for repairs/corrections and (b) machines that were previously sent in for regular check-up test's and/or replacement of circuit parts at customer's expense, so I haven't contacted him.

On the other hand, do you know of some methods I could try myself afield to determine if my machine's circuitry is operating correctly , especially the Ground Balance, Threshold and Sensitivity functions ?

Otherwise, do you know of a good source offering tune-up and service work on Tesoro units ? BTW, I live in Ohio, U.S.A..

Your help is appreciated !

ToddB64

 

[ToddB64]

Hi Monte

Thanks for your reply too regarding my opening post on this thread. Feel free to jump in with any answers or comments you can make to my post to Carl-NC. I need all the help I can get!

ToddB64

 

[Carl-NC]

Checking the threshold is simple as you can hear it. Sensitivity, just crank it up indoors and see if it gets noisy. Really the only thing that might even get out of whack is the GB, and even it's unlikely. Get a piece of ferrite and see if you can null it, then adjust off either side by at least a half-turn. If so, it's good.

I think Vince is not taking any more repairs and I have heard Keith Wills is the recommended repair venue. I'm sure it's fee-based only, no warranty work. The company is gone, the warranty is no good.

 

[ToddB64]

Checking the threshold is simple as you can hear it. Sensitivity, just crank it up indoors and see if it gets noisy. Really the only thing that might even get out of whack is the GB, and even it's unlikely. Get a piece of ferrite and see if you can null it, then adjust off either side by at least a half-turn. If so, it's good.

I think Vince is not taking any more repairs and I have heard Keith Wills is the recommended repair venue. I'm sure it's fee-based only, no warranty work. The company is gone, the warranty is no good.

Carl-NC,

Thanks for suggesting ways to check Threshold, Sensitivity and Ground Balance to see if they are operating properly; I'll give them a try !

Also, I appreciate your passing along Keith Wills name, owner of East Texas Metal Detectors, as a repair venue.

Is the kind of ferrite you spoke about something I would have to purchase from a company that makes blocks of it, or is it something I could obtain from a scrapped device, similar to obtaining free neodymium magnets by removing them from scrapped computer hard drives ?

ToddB64

 

[Monte]

Carl's replies are, as we know, spot-on. Just remember that the Sensitivity control on that model is only functional with the silent-search Discriminate mode. I always run mine at maximum and reduce it only as needed to handle any EMI noise in the Disc. mode. All Metal is at its full Sensitivity regardless of the control setting.

As for checking the GB, Carl suggested using a piece of ferrite and that would be handy, but most people don't have a hunk of it laying around. You can also use a more mineralized rock, or just pick a black asphalt parking lot since most of them are relatively more 'mineralized than regular pavement. Adjust the GB control to be as close to 'spot-on' as possible. Then, as Carl suggested, turn the GB control to bth the Positive [size=small](right or clockwise)[/size] and Negative [size=small](left or counterclockwise)[/size] direction while bobbing the coil from 6" to 1". It will usually only take a ¼ to ½ turn to hear the proper audio response.

I search ghost towns, homesteads and other old-use sites most of the time, and some of those are gold mining era locations where I encounter some higher mineralized environments. So I have gathered about 4 or 5 rock from them that I keep in my seminar tote, along with one from Australian gold fields, and those are what I have on-hand to check any detector with. Handy this time of year when it gets too cold to go out and play. Besides, all year long I do detector comparisons and a couple of these specimen rocks let me calibrate models, like Tesoro's Silver Sabre [size=small]micro[/size]MAX, that have an internal Ground Balance trimmer, so they are functional in a wide-range of hunting scenarios. The Bandido II [size=small]micro[/size]MAX has the benefit on the external manual GB control to let YOU be in control of a functional setting should you change search coils or locations where the ground conditions are much different.

I have a variety of detectors on hand right now from Fisher, Nokta / Makro, Teknetics, Tesoro, XP and White's, and on every detecting adventure I set out on at least one of my Tesoro's is loaded up as part of the Team. Usually it is the Bandido II [size=small]micro[/size]MAX which is my all-time favorite manual GB model they made. I hope your device is working well, and they seldom have an issue that isn't caused by operator mistreatment.

Monte

 

[Jerry-Wi]

You can find ferrite bars of various sizes in old transistor radios. Just look for a part that is a couple inches long and wound with lots of wire. This is the AM antenna. Also the EMI suppressors on older computer monitors which are fastened over the video cable. These usually are split so once you get the covering off they just come apart. I am sure there are other sources but those two come to mind.


Jerry

 

[ToddB64]

You can find ferrite bars of various sizes in old transistor radios. Just look for a part that is a couple inches long and wound with lots of wire. This is the AM antenna. Also the EMI suppressors on older computer monitors which are fastened over the video cable. These usually are split so once you get the covering off they just come apart. I am sure there are other sources but those two come to mind.

Jerry-Wi,

Thanks much for suggesting where to find ferrite bars !

Your reply triggered my thoughts to a Velleman Metal Detector Kit that I haven't assembled yet. This kit has a ferrite bar that I can use to test and adjust the Ground Balance on my Tesoro Bandido 2 Micromax, per Monte's suggestion.

Attached are a couple of pictures of the Kit K7102. One is a scanned picture of the label and ferrite bar to which I added dimensions using my Paint app. and the other shows the electronic components mounted on the PCB (Printed Circuit Board), both for the benefit of viewers information.

ToddB64

 

[ToddB64]

Monte,

Thanks for the info. in your subject post of November 23, 2019 08:00AM.

The instructions provided in your second paragraph (Copied [size=small]&[/size] Pasted below.) are very helpful !

"Adjust the GB control to be as close to 'spot-on' as possible. Then, as Carl suggested, turn the GB control to both the Positive (right or clockwise) and Negative (left or counterclockwise) direction while bobbing the coil from 6" to 1". It will usually only take a ¼ to ½ turn to hear the proper audio response."

HH !

ToddB64

 

[slingshot]

You can find ferrite bars of various sizes in old transistor radios. Just look for a part that is a couple inches long and wound with lots of wire. This is the AM antenna. Also the EMI suppressors on older computer monitors which are fastened over the video cable. These usually are split so once you get the covering off they just come apart. I am sure there are other sources but those two come to mind.


Jerry

Great info!

 

[ToddB64]

Checking the threshold is simple as you can hear it. Sensitivity, just crank it up indoors and see if it gets noisy. Really the only thing that might even get out of whack is the GB, and even it's unlikely. Get a piece of ferrite and see if you can null it, then adjust off either side by at least a half-turn. If so, it's good.

I think Vince is not taking any more repairs and I have heard Keith Wills is the recommended repair venue. I'm sure it's fee-based only, no warranty work. The company is gone, the warranty is no good.

Carl-NC,

In the Beep & Dig Detecting Forum, my thread titled "Ground Balance, Threshold and Sensitivity Settings ", dated
November 18, 2019 05:02PM, regarding the Tesoro Bandido II µMax, you replied "Get a piece of ferrite and see if you can null it, then adjust off either side by at least a half-turn. If so, it's good.".

The Bandido II µMax has ED120 (Extended Discrimination) and I presume that means it doesn't discrimate targets containing iron down to ED180 on the arc like the Compadre. Also, I assume by "a piece of ferrite" you were referring to something like a radio antenna core that's highly saturated with iron, more so than a typical iron nail, so isn't it a foregone conclusion that the Bandido II µMax with ED120 is NOT going to be able to "null" a piece of ferrite like a radio antenna core ?

I'm in no way challenging your reply; I'm sure it's a case of my lack of and/or misunderstanding of the technical aspects involved.

Please explain and thanks in advance for your help Carl.

ToddB64

 

[Monte]

Carl-NC,

In the Beep & Dig Detecting Forum, my thread titled "Ground Balance, Threshold and Sensitivity Settings ", dated
November 18, 2019 05:02PM, regarding the Tesoro Bandido II µMax, you replied "Get a piece of ferrite and see if you can null it, then adjust off either side by at least a half-turn. If so, it's good."

I have some ferrite samples, somewhere, but prefer to just adjust the GB for the sites I am hunting. I do, however, have a few specimen rocks from some of the more challenging ground mineral areas I hunt and I often use them to check GB adjustability and detector performance. On the Bandido II [size=small]micro[/size]MAX, as well as almost all other Tesoro models, I would adjust the GB in the Threshold-based All Metal mode to be 'spot-on' or ..if anything .. just very slightly negative in the All Metal mode. I would not increase or decrease the GB from 'spot-on' by ½ turn. That model uses a 3¾-turn GB pot whereas the original Bandido and Bandido II use a 10-turn GB pot and might still function OK with a ½-turn either side, but not the 3¾-turn pot.

Why do I suggest this, you might ask? Simple: Most Tesoro models have the Discriminate mode tied in with the GB adjustment, but the Disc. mode has a somewhat positive off-set from the All Metal mode. Thus, if you GB 'spot-on' in the Threshold-based All Metal mode, the Disc. mode is already slightly positive. If you turn the GB control an additional ½-turn more positive, that can often make the GB in the Disc. mode way too positive and it might not give a positive response to a US silver Dollar, and could even not respond to a Half-Dollar or, sometimes, even a Quarter.

The way Tesoro circuitry was designed [size=small](generally with most models)[/size] a peak-performance GB setting made in the silent-search Discriminate mode will have the Threshold-based All Metal mode just a bit negative. Still functional for Pinpointing targets, which is good because most folks use the Disc. mode almost exclusively.

The Bandido II µMax has ED120 (Extended Discrimination) and I presume that means it doesn't discrimate targets containing iron down to ED180 on the arc like the Compadre.

ED-180 means ALL of the 180° "arc' [size=medium](upper portion of a sine wave)[/size] is Accepted, from Ferrous range on to the higher-conductive Non-Ferrous range, such as silver.

ED-120 means the lower 60° of the 180° 'arc' is NOT Accepted, and therefore they are rejected. That would be using the minimum Disc. setting on the Bandido II [size=small]micro[/size]MAX where most nails and most ferrous-based targets would be ignored, aka Discriminated or Rejected. Lower-conductive non-ferrous objects, such as small, thin foil or thin gold chains, etc., would just be Accepted at that minimum ED-120 Disc. setting on up the conductivity range to higher-conductive silver dollars. So at the minimum Disc. setting with ED-120 Disc., nails and most common iron IS going to be rejected.

NOTE: As with just about any detector offered with motion-based Discrimination, we can still have issues with some man-made ferrous-type objects, such as crimp-on Bottle Caps, round iron washers, etc.

Also, I assume by "a piece of ferrite" you were referring to something like a radio antenna core that's highly saturated with iron, more so than a typical iron nail, so isn't it a foregone conclusion that the Bandido II µMax with ED120 is NOT going to be able to "null" a piece of ferrite like a radio antenna core ?

The ferrite sample is used to adjust the Ground Balance in the All Metal mode, not to check the Discriminating abilities of the Discriminate mode.

Now, that said, I have used a ferrite sample, just as I do a very mineralized rock, to adjust the Ground Balance in the silent-search Discriminate mode. That is a technique I described as "Power Balancing" about 35 years ago or so. With my Bandido's I usually make a quick GB in the All Metal mode to be 'spot-on' or just very slightly negative. But I use 'Power Balancing' in the Disc. mode a little more often than GBing in All Metal just to be certain I have a peak-performance GB setting since I am mainly searching in the motion-based Discriminate mode.

I'm in no way challenging your reply; I'm sure it's a case of my lack of and/or misunderstanding of the technical aspects involved.

Please explain and thanks in advance for your help Carl.

ToddB64

I'm naturally not Carl, but I encourage you to not get too lost in terminology or definitions, or worry about the Bandido II µMAX as it is really rather simple. Just go out hunting and adjust the GB to the particular site you are hunting. Quite often I adjust the GB on mine to be 'functional' for my area and just turn it on and start hunting in most places. If there has been a significant change in ground mineral make-up, I'll know it right away and can make a GB correction in 5 to 10 seconds. If you're stuck indoors during the winter wherever you are, you can use a ferrite specimen or a good rock and just practice Ground Balancing at home.

Monte

 

[ToddB64]

Carl-NC,

In the Beep & Dig Detecting Forum, my thread titled "Ground Balance, Threshold and Sensitivity Settings ", dated
November 18, 2019 05:02PM, regarding the Tesoro Bandido II µMax, you replied "Get a piece of ferrite and see if you can null it, then adjust off either side by at least a half-turn. If so, it's good."

I have some ferrite samples, somewhere, but prefer to just adjust the GB for the sites I am hunting. I do, however, have a few specimen rocks from some of the more challenging ground mineral areas I hunt and I often use them to check GB adjustability and detector performance. On the Bandido II [size=small]micro[/size]MAX, as well as almost all other Tesoro models, I would adjust the GB in the Threshold-based All Metal mode to be 'spot-on' or ..if anything .. just very slightly negative in the All Metal mode. I would not increase or decrease the GB from 'spot-on' by ½ turn. That model uses a 3¾-turn GB pot whereas the original Bandido and Bandido II use a 10-turn GB pot and might still function OK with a ½-turn either side, but not the 3¾-turn pot.

Why do I suggest this, you might ask? Simple: Most Tesoro models have the Discriminate mode tied in with the GB adjustment, but the Disc. mode has a somewhat positive off-set from the All Metal mode. Thus, if you GB 'spot-on' in the Threshold-based All Metal mode, the Disc. mode is already slightly positive. If you turn the GB control an additional ½-turn more positive, that can often make the GB in the Disc. mode way too positive and it might not give a positive response to a US silver Dollar, and could even not respond to a Half-Dollar or, sometimes, even a Quarter.

The way Tesoro circuitry was designed [size=small](generally with most models)[/size] a peak-performance GB setting made in the silent-search Discriminate mode will have the Threshold-based All Metal mode just a bit negative. Still functional for Pinpointing targets, which is good because most folks use the Disc. mode almost exclusively.

The Bandido II µMax has ED120 (Extended Discrimination) and I presume that means it doesn't discrimate targets containing iron down to ED180 on the arc like the Compadre.

ED-180 means ALL of the 180° "arc' [size=medium](upper portion of a sine wave)[/size] is Accepted, from Ferrous range on to the higher-conductive Non-Ferrous range, such as silver.

ED-120 means the lower 60° of the 180° 'arc' is NOT Accepted, and therefore they are rejected. That would be using the minimum Disc. setting on the Bandido II [size=small]micro[/size]MAX where most nails and most ferrous-based targets would be ignored, aka Discriminated or Rejected. Lower-conductive non-ferrous objects, such as small, thin foil or thin gold chains, etc., would just be Accepted at that minimum ED-120 Disc. setting on up the conductivity range to higher-conductive silver dollars. So at the minimum Disc. setting with ED-120 Disc., nails and most common iron IS going to be rejected.

NOTE: As with just about any detector offered with motion-based Discrimination, we can still have issues with some man-made ferrous-type objects, such as crimp-on Bottle Caps, round iron washers, etc.

Also, I assume by "a piece of ferrite" you were referring to something like a radio antenna core that's highly saturated with iron, more so than a typical iron nail, so isn't it a foregone conclusion that the Bandido II µMax with ED120 is NOT going to be able to "null" a piece of ferrite like a radio antenna core ?

The ferrite sample is used to adjust the Ground Balance in the All Metal mode, not to check the Discriminating abilities of the Discriminate mode.

Now, that said, I have used a ferrite sample, just as I do a very mineralized rock, to adjust the Ground Balance in the silent-search Discriminate mode. That is a technique I described as "Power Balancing" about 35 years ago or so. With my Bandido's I usually make a quick GB in the All Metal mode to be 'spot-on' or just very slightly negative. But I use 'Power Balancing' in the Disc. mode a little more often than GBing in All Metal just to be certain I have a peak-performance GB setting since I am mainly searching in the motion-based Discriminate mode.

I'm in no way challenging your reply; I'm sure it's a case of my lack of and/or misunderstanding of the technical aspects involved.

Please explain and thanks in advance for your help Carl.

ToddB64

I'm naturally not Carl, but I encourage you to not get too lost in terminology or definitions, or worry about the Bandido II µMAX as it is really rather simple. Just go out hunting and adjust the GB to the particular site you are hunting. Quite often I adjust the GB on mine to be 'functional' for my area and just turn it on and start hunting in most places. If there has been a significant change in ground mineral make-up, I'll know it right away and can make a GB correction in 5 to 10 seconds. If you're stuck indoors during the winter wherever you are, you can use a ferrite specimen or a good rock and just practice Ground Balancing at home.

Monte

Thanks Monte ! I'll make a hard copy of your reply, then re-read, digest and let it all sink in, and practice inside......it's 40°F outside where I live in Georgetown, Ohio today.

The weather is supposed to gradually get warmer next week up to 50°F, and with a high of 57°F by Christmas, Dec. 25th., so I plan to catch a day or two of metal detecting with the Bandido ll µMax.

ToddB64

 

[Carl-NC]

I would not increase or decrease the GB from 'spot-on' by ½ turn. That model uses a 3¾-turn GB pot whereas the original Bandido and Bandido II use a 10-turn GB pot and might still function OK with a ½-turn either side, but not the 3¾-turn pot.

Sorry for the slow reply, just saw this. I re-read my earlier post and it certainly wasn't clear.

The reason I suggested GB +/- ½ turn is to ensure the GB control has enough range. If you GB a piece of ferrite, and then can still turn the knob +/- ½ turn without hitting the end of the control range (which, on a 3¾-turn pot, is soft and a little difficult to feel), then the GB should have enough range to handle any ground. OTOH, if you GB to ferrite and the GB control is right up against the end-of-range, then you probably want to go inside and adjust the range offset. An AM radio stick will work, although an EMI core would be better.

 

[ToddB64]

I would not increase or decrease the GB from 'spot-on' by ½ turn. That model uses a 3¾-turn GB pot whereas the original Bandido and Bandido II use a 10-turn GB pot and might still function OK with a ½-turn either side, but not the 3¾-turn pot.

Sorry for the slow reply, just saw this. I re-read my earlier post and it certainly wasn't clear.

The reason I suggested GB +/- ½ turn is to ensure the GB control has enough range. If you GB a piece of ferrite, and then can still turn the knob +/- ½ turn without hitting the end of the control range (which, on a [size=[x-small]¾[/size]-turn pot, is soft and a little difficult to feel), then the GB should have enough range to handle any ground. OTOH, if you GB to ferrite and the GB control is right up against the end-of-range, then you probably want to go inside and adjust the range offset. An AM radio stick will work, although an EMI core would be better.

Carl-NC,

Thanks for the clarifications !

However, in reference to your above comments in blue, if using either an AM radio ferrite stick or an EMI ferrite core (Which I assume a split core type would qualify.) and the Bandido II µMax 3[sup]3/4[/sup] turn GB control dial is right up against the end-of-range, are you still saying "then you probably want to go inside and adjust the range offset" ?

I've read cautions/warnings in the past that advise the average person against trying to adjust the inside GB control in particular, because without the knowledge and experience they could really mess things up to the extent that professional service is required for correction. Maybe these cautions were the result of some "ham-handed" inexperienced person making the adjustment...dunno.

Your comments on this please.


ToddB64

 

[Carl-NC]

I've read cautions/warnings in the past that advise the average person against trying to adjust the inside GB control in particular, because without the knowledge and experience they could really mess things up to the extent that professional service is required for correction. Maybe these cautions were the result of some "ham-handed" inexperienced person making the adjustment...dunno.

This mostly pertains to a fixed-GB detector, where messing with the preset GB can make the detector unusable. But even with a variable-GB detector you need to know what you are doing. My initial reply was only to your question of how to determine if the controls are operating correctly. Most likely they are, but if they are not, then the way to fix them is a whole other conversation.

 

[ToddB64]

I've read cautions/warnings in the past that advise the average person against trying to adjust the inside GB control in particular, because without the knowledge and experience they could really mess things up to the extent that professional service is required for correction. Maybe these cautions were the result of some "ham-handed" inexperienced person making the adjustment...dunno.

This mostly pertains to a fixed-GB detector, where messing with the preset GB can make the detector unusable. But even with a variable-GB detector you need to know what you are doing. My initial reply was only to your question of how to determine if the controls are operating correctly. Most likely they are, but if they are not, then the way to fix them is a whole other conversation.

Thanks for clarifying that Carl.

Due to freezing temps, I haven't checked my Bandido II µMax controls yet to see if they are operating correctly, but asap I will, using the methods you and Monte kindly gave me earlier.

Wishing you a Great Christmas and New Years !

ToddB64

 

[ToddB64]

I would not increase or decrease the GB from 'spot-on' by ½ turn. That model uses a 3¾-turn GB pot whereas the original Bandido and Bandido II use a 10-turn GB pot and might still function OK with a ½-turn either side, but not the 3¾-turn pot.

Sorry for the slow reply, just saw this. I re-read my earlier post and it certainly wasn't clear.

The reason I suggested GB +/- ½ turn is to ensure the GB control has enough range. If you GB a piece of ferrite, and then can still turn the knob +/- ½ turn without hitting the end of the control range (which, on a 3¾-turn pot, is soft and a little difficult to feel), then the GB should have enough range to handle any ground. OTOH, if you GB to ferrite and the GB control is right up against the end-of-range, then you probably want to go inside and adjust the range offset. An AM radio stick will work, although an EMI core would be better.
__________________________________________________________________________________________________________________________

Carl-NC,

Re your ferrite core preference I colored blue above, here's a link I've been reading https://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection, that says "There are two basic ferrite material groups: (1) Those having a permeability range from 20 to 850µ are of the Nickel Zinc (NiZn) class (mix 43, 52, 61), and (2) those having initial permeabilities above 850µ are usually of the Manganese Zinc (MnZn) class (Mix 31, 73, 75).", andl Carl if you click-on the Link it gives additional information regarding the properties of the basic ferrite material groups.

Now, I would like to obtain an EMI core for testing the GB circuit of my Bandido 2 µMax to get "better" results, but before shopping the Internet I have a question for you.

Question: Which "permeability micro-range and mix" do you think I need ?

Thanks,
Toddb64