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Ground balance on SD 2100 (Reg)

A

Anonymous

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Please forgive the minelab question, I know Reg has done lots testing with the GQ SS and the SD 2100 and I hope he can help. I wish someone would come up with a mod for the 2100. Some areas where we're hunting in Arizona won't ground balance on ch 2, it runs out of turns or won't turn far enough. I am using a DD coil, I usually end up running a mono on ch 1 and missing nuggets smaller than 1.5 dwt. I don't see why you can't replace the 10 turn pot with a 15 turn pot to give it a wider area or more turns so it will GB on ch 2. Reg or anyone that can help I would appreciate it. Thanks, Russ
 
Hi Russ,
Just changing the 10 turn pot for a 15 turn pot, won't alter the ground balance range. All it will do is make the adjustment finer. If there is a fixed resistor in series with the pot, changing the value of this should alter the adjustment range. I will have a look at the SD2100 that I have here, and see if that is the case.
Eric.
 
HI Russ,
To be honest, I haven't looked inside my Dad's SD 2100 so I am not sure just what is being done with the GB circuit. Hopefully, Eric will find an answer and solution. He is far more familiar with the inside of the SD than I am.
To be honest, I glean most of my SD info or ML PI info from their patents. I will then try some experiments to see if their machines follow the patterns I expect if certain techniques are used in testing. This pretty well tells me what they are doing.
Now, I am really surprised that you are not able to ground balance when using the DD coil. It has been a while since I tried the SD in AZ but I don't remember anywhere where the machine wouldn't ground balance and we have hunted across a fairly wide part of AZ. There were a couple of places that balancing was a problem which made using a DD more desireable.
Now, I did find a couple of places where the basalt was bad enough that one had to constantly adjust the GB or it would be out of balance, but that was because I was going from basalt rock to basalt rock and they all seemed like they were different. So, the machine never was in good ground balance for any length of time. One particular area was up Antelope creek north of Rich Hill. About the only way I was able to hunt that area was with my modified Tesoro Lobo in the discrimination mode and then, I had to go very slowly. I never did try my GB 2 there but I suspect it would have worked in the disc mode also.
It is possible that your SD has a problem also. If so, I suspect the factory might be the only ones who would be able to really help you. ML is pretty secretive about their circuitry. Do you know if other SD 2100 owners are having the same problems as you in the particular areas?
I have heard of SD 2000's getting or running out of balance when they modified the units to operate with a faster crystal. I am wondering, did you have the 2100 modified?
Reg
 
Hi Reg,
There are only two area that we have trouble with GB on ch 2. Most areas aren't a problem, one area we found 18 ounces and the other is a good area for big nuggets also. It has course black sand in the washes and the 2100 will not GB in the wash and it is on the edge on ch 2 on the flat ground giving false ground signals. The GP 3000 with a DD Pro will only run by swicthing to normal/normal and it still gets ground noise, I never tried the salt mode before I sold it. When you are hunting big deep nuggets you can't have any ground noise at all it just won't work.
I do have a Ismael Jones adjustable reg that pushes the volts to 8.5 v. The GB had the same problem with the 7.3 v coiltek reg. My brother Scott's 2100 has the same GB ploblem in these 2 areas, so there is nothing wrong with the detectors, they fing gold just fine. <img src="/metal/html/grin.gif" border=0 width=15 height=15 alt=":grin"> Thanks for any help you or Eric can give.
H.H. Russ
 
Thanks Eric, looking forward to what you can come up with.
Regards, Russ
 
G'day Russ,
Just a quick question; What brand of DD coil are you using when you run out of GB on the second pot?
Regards,
Jonathan Porter
 
G'day Jonathan,
The old style Coiltek and the new DD Pro. I would like to try A 16" DD NuggetFinder, but haven't been able to yet.
Russ
 
G'day again Russ,
If you open the end cap of your 2100 I think you will find that the boards are painted a different colour than white (standard colour).
There was an issue here in OZ a few years back with a certain batch number of SD2100's running out of GB on the number 2 pot with Coiltek DD's. I'm not sure if this problm surfaced with the Minelab DD's or not, I am surprised that the newer Pro coil's are causing the same problem.
By checking the paint on the boards you will soon find out if this is the case. I think the different coloured paint was black and caused the problem because it was conductive (hearsay from other prospectors).
Let me know how you get on, it would be intersting to see how a NF DD performed because of the different material used ih the windings.
Hope this helps,
Jonathan Porter
 
G'day Jonathan,
I read about that a few years ago that a certain batch of 2100's that woundn't GB with a Coiltek coil and I was curious and pulled off the end cap and found that they are white on both mine and my brother's 2100's. I was hoping you had something else up your sleeve to get the 2100 to GB on ch 2. <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=":)">
Thanks, Russ
 
Why not borrow Bill Southern's Nugget Finder DD for a test? That would decide the matter pretty quickly!
Potholes Bob <img src="/metal/html/wink.gif" border=0 width=15 height=15 alt=";)">
 
Hi Russ,
You've probably already tried this, but the higher voltage makes the SD's much more sensitive so I'd try kicking the voltage down a bit and see what effect that had on the ground balance. Just a thought. Regards, RD
 
Hi RD,
The 2100 had the same GB problem with the 7.3 v Coiltek system and a stck ML DD. I haven't tried it with the stock 6 v battery, I don't ever run it that way, the 2100 in stock form needs help. It needs an amp and boost the voltage to 7.3 v - 7.8 v which eliminated a lot of interferance they get, you know the infamous Wwoo Wwoo Wwoo and as you said it increases sensitivity, but I'll try the IJ adjustible reg at 6.9 v next time I'm in that area.
Russ
 
I talked to Bill a year ago and Bill S will let you test a coil if you tag along with him to LSD. The ground at LSD won't tell me how the NF DD will handle the black sand where I hunt. Besides I own at least 10 coils and hate to buy one more to see if it will run on hot ground. If Eric can find another fix to the GB 2 problem I'll have plenty of coils to use. It might be an easy fix for Mr Foster! <img src="/metal/html/lol.gif" border=0 width=15 height=15 alt=":lol"> Lets wait and see what Eric says.
 
Hello Russ , open your machine and check what value the GB pots are , if they are 50k pots then replace them with 100k pots , you will lose a bit of sensitivity ( not much ) but you will be able to balance the machine a lot better and if this does not cure the problem try getting hold of a salt/anti-interference coil from coiltek and running with that because your problem may be due to dissolved salt mineralization in that area. Did you say you were near a water source ?
Regards TJ.
 
Hi Russ,
I am not sure an extended ground balance will solve the problem. It would be nice to be able to try it, and it might help some, but right now I am guessing the problem will still be there.
I am thinking of two different reasons why all the machines are acting basically the same way. The first is, the "black sand" isn't the typical black sand. If so, coarse black sand at the area might be a "target" of some kind. Silver ore comes to mind, but more likely it is something else that is readily detected by a PI. In other words, the black sand isn't the more typical magnetite granules.
If this is the case, then extending the GB will not solve the problem. Instead, it might take advancing the delay to minimize it and even then, the problem will most likely still be there.
The second idea that comes to mind is the ground has distinct stringers of black sand and something significantly different such as a maghemite type clay base stringer . So, the area is striped with the two significantly different matrix conditions. If this is the case, then it is possible that extending the GB will not help here either.
GB's, including the ML's, are not perfect. They can compensate for quite a bit of difference between ground conditions, but generally, they work best where there are more gradual changes. Sudden changes such as an area striped with significantly different ground compositions will still generate a response. In other words, the GB is really working within range but due to design will but not sufficiently compensate for the "sudden" distinctively different conditions. One reason they are designed this way is targets, such as gold nuggets, generate a "sudden" change. So to be able to hear the very subtle changes better, the ground compensation capability is sometimes slowed down to minimize affecting those very weak sudden nugget caused changes.
Anyway, these are a couple of thoughts I have on the subject. I could be off in left field but I don't think so.
Reg
 
Reg, your line of thought on the cause of the problem is very interesting. Would you say that a fast autmatic balancing detector such as the Minelab GP Extreme would be able to handle such extreme ground fluctuations?
Black sand is remarkable Reg! When I walked into a prospecting shop in Mesa Arizona, in 1995 looking for a detector that would handle the difficult AZ. ground, I brought my Fisher Gold Bug 1 along with me. The owner took the new XT-17000 , and we went into the vacant lot outside. The salesman had me ground balance the GB1, and then he laid some newspaper on the ground and proceeded to pour a bucket of black sand on the paper. Then he asked me th throw my car keys on top of the black sand and try to "detect the keys. To my absolute astonishment, the little GB1 was dead silent as it passed six inches above those car keys! Then he placed the XT17000 in Auto Tracking, passed it a foot above the pile of black sand and car keys, and the 17000 just howled! Well, obviously, if a gold nugget, which we tried, was in that black sand, where nuggets often are,forget it! Five minutes later I walked out minus $1000, but with that hot new 17000! <img src="/metal/html/lol.gif" border=0 width=15 height=15 alt=":lol">
Potholes Bob <img src="/metal/html/wink.gif" border=0 width=15 height=15 alt=";)">
 
Hello Reg,
I think the area is alkali soil mixed with iron stringers, and all the black sand concentrates in the washes, any one of various soils found in arid regions. I think the area has both black alkali soil and white alkali soil. The main wash that cuts through the area has course black sand, it will stick on my earth magnet about about the size of a big furry tennis ball. The 2100 will almost balance out on the flat ground, but will go crazy in the bottom of the wash. All of the gold in the wash was found by using a mono on ch 1. Minelab knows that certain ground will not GB on ch 2 on the 2100. This is what instruction manual states... that a dark orange/reddish material or clay, or charcoal can produce a sudden signal variation. If the ground is extremely variable and causes the detector to be very noisy you may try operating with the search switch set to balance 1. Whilst this will reduce noises caused by the varying mineralisation, some nuggets will not be detected in balance 1 or balance 2, but only when the search switch is set to search.
TJ has a great idea to try the Coiltek salt/interferance coils. Can someone explain TJ's idea of the 50k pot verses the 100k pot and would I have to change both pots 1 and 2?
Thank for the help! Regards, Russ
 
Thanks TJ,
I think the Coiltek salt/anti-interference coil is a great idea, I will try to get a hold of one. I know nothing about electronics so someone will hopfully explain the 50 k pot verses the 100 k pot, the 2100 can't aford to lose any sensitivity. Thanks again, Russ
 
Hi Russ,
I got to thinking and trying to come up with a method of determining just what type of problem exists. Anyway, a couple of ideas came to mind.
First, if the situation is some form of stiping, it is generally consistent and in line with water flow, so one could try testing by scanning the area from two different directions and comparing the two. One method would be to walk down the wash and scan side to side. This would cause the center overlap zone on a DD to pass over each individual stripe, thus producing the strongest signal.
Now, if the direction of search was changed by 90 degrees, then part of each stripe would be under the overlap zone most of the time. This should produce the least amount of ground signal.
The second idea is if the "black sand" is really something else that is a legit target, I suspect that because of its size, just raising the coil a couple of inches would greatly reduce the problem. In other words, the saying "swing low and slow" may be counter productive at this location.
Raising the coil has a much greater effect on small targets than on larger ones, so if large gold is the objective, then just elevating the coil more above the ground might help a whole lot. It sounds like the opposite thing to do, but in some cases, it is the proper solution.
Now, if a weak signal is encountered, one can lower the coil and test again. If the signal increases signficantly, there is a high probability the target is small and close to the surface, rather than a large deep object.
Anyway, hopefully, the ideas mentioned will generate more ideas which may help with the problem.
If nothing else, one can search an area twice, once using the tradional "low and slow" approach and the second, with the coil elevated. I wouldn't be afraid of elevating the coil up to 6" or so. This may sound like a lot, but we really do it all the time anyways, just passing over rocks. in rocky areas. We just don't notice it.
Reg
 
What I didn't add was, if that black sand was in a pocket along with gold nuggets, and it was covered by regular soil so that you couldn't see it and manually rebalance, you would pass right over it and never know it! Oh, you might notice a slight quieting as if you had gone over a negative hot rock, but that gold would never have triggered a detector like the Gold Bug 1!
Potholes
 
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