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The Tale Of Two F75's (One For Sale)


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When it comes to large scale manufacturing you are simply going to have some units that outperform others...its a simple numbers game. It isn't that the other units are necessarily performing poorly, rather, it is that there seem to be some rarely exceptional units in the mix.

 

I had one of the original F75's without the DST or updates and it was a performer, even in hot ground it was a little noisy but not intolerable, I kept it around though because of the depth and sensitivity to small gold. I have a friend that had an F-75 LTD DST that he hated and wasn't anywhere near as sensitive.

 

In all metal my old F75 would hit on a .3 Gram nugget at about four inches with the stock coil which is ridiculous - with the similar sized coil on my Teknetics G2 I literally had to be brushing this odd little nug against the coils surface to even obtain a response. I was a dummy and sold it for a good offer and now at times when using the G2 I find myself missing the old F75. 

 

It's not just one manufacturer either; you can single out any machine from any number of manufacturers and find the same thing. A similar example is the Garrett Infinium. One of the biggest problems for Garrett I believe is that they had some very poor units off the line mixed in with some other units that perform exceptionally. Obviously, these machines led to a barrage of negativity that still seem to be present in it's mention. Some people that think that the Infinium is a piece of Chinese garbage while others believe it is the greatest thing since sliced bread simply because they are obtaining different results, and granted sometimes, but not always is it the skill of the operator but the quality of the manufacturing or components themselves that lead to different results.

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I believe the biggest sleeping dog in detectors is the whole issue of quality control both in the detectors and especially in the coils. Substandard units are very common and account for some of the widely varying opinions on detectors. There are many less knowledgable people using detectors or coils that are performing poorly and they do not even know it. It seems the problem has been getting worse but I can't tell if that is true or simply a side effect of the Internet and better cross checking and reporting by users. All the major manufacturers have made big fumbles in recent years on new detector releases so none can really be singled out. In general the more machines a company sells the more issues arise just from sheer numbers sold.

I disagree with the concept that rare hot units are making all the rest look bad. The members of this and many other forums are people buying top end "flagship" detectors and each and every one should be performing to top specifications. If not they should not be getting out the door. Or is it they are slapping together cheap low quality components and it is just a crapshoot getting a top performing unit? Sorry, that is what we expect from cheap detectors, not ones costing $1000 and more.

It really is so bad these days that in general I would advise a newbie to simply not buy a new model detector for a minimum of about 6 months after release just to let the bugs shake out. The problem of course is the "early adopter" being a guinea pig for the manufacturers and becoming in effect the last ten feet of the production line.

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I believe the biggest sleeping dog in detectors is the whole issue of quality control both in the detectors and especially in the coils. Substandard units are very common and account for some of the widely varying opinions on detectors. There are many less knowledgable people using detectors or coils that are performing poorly and they do not even know it. It seems the problem has been getting worse bit I can't tell if that is true or simply a side effect of the Internet and better cross checking and reporting by users. All the major manufacturers have made major fumbles in recent years on new detector releases so none can really be singled out. In general the more machines a company sells the more issues arise just from sheer numbers sold.

I disagree with the concept that rare hot units are making all the rest look bad. The member of this and many other forums are people buying top end "flagship" detectors and each and every one should be performing to top specifications. If not they should not be getting out the door. Or is it they are slapping together cheap low quality components and it is just a crapshoot getting a top performing unit? Sorry, that is what we expect from cheap detectors, not ones costing $1000 and more.

It really is so bad these days that in general I would advise a newbie to simply not buy a new model detector for a minimum of about 6 months after release just to let the bugs shake out. The problem of course is the "early adopter" being a guinea pig for the manufacturers and becoming in effect the last ten feet of the production line.

 

Re-reading my post I guess I did, however, it was not my intent to convey there were "super units." You did a better job of stating what I was trying to.

 

I can't say it is the case for any/every detector company as I never have worked for one, but I know a lot of electrical components, chipsets, etc are often sourced from overseas to save money these days. It's not always to save a buck either, rather, a lot of things cannot be found domestically (at least in the case of the US.) Certain things are simply not produced here anymore. I know the quality is really hit or miss in import components, often far greater than the often stated +/- 1%. How many less than perfect components on a detectors PCB is enough to create these fluctuations in performance? Not many.

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Wow I wasn't able to get that kind of service from fisher...10 emails 5 phone calls on a gb2 that was less than a yr old... told me they would get back to me and here it is 7 mths later and still no word...not to mention they acknowledged their fault .. ..sold the machine cause they just peed me off with their attitude...but that's me...good to hear someone got results..

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Wow I wasn't able to get that kind of service from fisher...10 emails 5 phone calls on a gb2 that was less than a yr old... told me they would get back to me and here it is 7 mths later and still no word...not to mention they acknowledged their fault .. ..sold the machine cause they just peed me off with their attitude...but that's me...good to hear someone got results..

 

Man...sorry to hear about your NON-resolution.  I'm kind of surprised to hear it actually.  I have heard numerous complaints about Fishers QC, but very few about the customer support.   When I sent an email I copied everyone I could find a Fisher email address for.  Not just customer support.  I had several phone conversations with Gene Scullion, super nice guy and very willing to help.

 

Sorry you had to dump the GB2.

 

Kenny

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I know my machine has been around for a few years now but this Latest format seems the hottest yet, I asked whites about it and they never tell you much and the info I got was more of a Coded Message than a statement, All I Know is it see's 1.0 grain pickers at 1 to 2 inches and a 0.34 gram Picker at 6 to 7.5 inches and it can see my hand between 4 to 6 inches+,

And all of them Lead Test Pieces I used for testing my GMT My MXT can see them, so I know they have been hot rodding these machines,

John

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Hi Kenny… your comments above are right on the money, at least concerning typical mafic negative hotrocks as you’ve described. Over this way, we normally encounter massive diabase beds, and to a much lesser extent other mafics such as basalt and occasional float pretty much comprised of magnetite. These are non-conductive iron-mineralized rocks to which my comments below apply. Other positive responses produced by electrically conductive hotrocks such as a commonplace iron sulfide ‘pyrrhotite’ for example, are entirely different propositions. Obviously there will be a wide variation in discrimination levels to eliminate their signals, depending on the mineral type, quantity in a given rock sample, structure, size, shape, and so on. How a metal detector’s discrimination modes process signals is certainly a key factor as well.

 

We frequently search diabase beds or substrates where the F75 ground balance ranges between GB85 and GB93 when using the 10” elliptical concentric coil for example. Usually the Fe3O4 readout hangs just below maximum at 1.0 % magnetite equivalent, but there are individual chunks whose magnetic strength varies from normally encountered values. Keep in mind that many of these rocks are large and some weigh up to several hundreds of pounds… one cannot always simply kick them out of the way and carry on searching. A minimum 99% of the rocks in the photo below are comprised of diabase.

 

post-320-0-33151900-1437254691_thumb.jpg

 

Operating in those conditions, invariably both positive and negative hotrock signals are generated in the motion all-metal mode, depending on just where the GB setting is positioned at any given moment. We’ve experienced identical results to yours… that negative mafic hotrocks are silenced in zero discrimination regardless whether employing DE, PF, or JE modes, and regardless of magnetic strength. My original F75 has no boost mode, but your observations above are unequivocal… 

 

Positive hotrock signals produced by these same mafic rock types are a different matter, but normally these signals only occur in significant numbers here when searching diabase substrates, such as occurs in many of our extensive tailings disposal areas. We find that such signals require a minimal discrimination setting of “1” in DE and PF modes to silence them regardless of magnetic strength. But in JE mode… the maximum iron discrimination setting of “15” is required to eliminate such signals, again… regardless of magnetic susceptible strength. 

 

It has been awhile since we last spoke on the old AMDS forum Kenny, so this has been a real pleasure for me. Thanks again for an informative and interesting thread discussion, and to reiterate… I’m glad everything worked out satisfactorily for you.

 

Jim.

 

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Thank you Jim for the in depth, excellent information.  Your right...it has been awhile since the AMDS forum.

 

This F75 is a new adventure for me.  I'm still in the learning mode but I am seeing things I like for sure.  As an example...when compared to the AT Gold that I use.  When in hot rocks, the AT will of course announce them loud and clear in All Metal mode, and similar to the F75, when the AT is switched to disc 1 the hot rocks disappear.  But...the major difference is when the AT is switched to disc mode it automatically loses 2 to 3" depth right off the top (little pun there).  I have played with this on an in ground target.  While swinging the AT above a buried target, clearly audible in all metal, switch over to disc 1 and it disappears.  The impact of switching between modes on the F75 doesn't appear to be nearly as dramatic.  I haven't had enough time on the F75 yet to verify the differences on an in ground target.

 

There are so many combination of settings on the F75 and lately it's been a large time span between detecting sessions, I can't keep track.  For the most part in my local area I run in JE mode.  It seems to offer the best combination of swing speed and depth in the hotter soils here.  Been using the 2L tone selection and the F75 keeps surprising me how well it separates in the nails.  I can't wait until I gain more proficiency with this detector and really understand what it is telling me.

 

I'm really impressed with the number of bullets I have found with this F75.  It really locks on and I pretty much know what it is before digging.  If it will do that with bullets, it will darn well do it with gold :-)

 

Great chatting again Jim.  Take care and keep us posted on your adventures.  I always enjoy your posts.

 

Kenny

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Hi Kenny… just another few remarks in response to your findings to date. The F75 discrimination modes do process ground mineral and target signals differently. Employing zero discrimination in any F75 discrimination mode to eliminate those mafic negative hotrock signals, while simultaneously acquiring the best possible discrimination mode detection depth and making good use of iron tones… is a great combination. Aside from masking issues, keep in mind that iron tones will sometimes be applied to non-ferrous targets at depth… particularly in elevated ferromagnetic substrates. Listen for any hint of regular tones and although it can be frustrating at times… try to habituate yourself to digging the weaker iron tones if you think the conditions / prospects warrant it.

Nowadays I rarely use discrimination modes, unless small iron tidbits, small nails or beds of numerous hotrocks are troublesome to the point of distraction. Most of our searching is done in the motion all-metal mode for its superior sens / depth and that especially applies when compared to discrimination modes in areas of higher ground mineral magnetic strength. At most times we can ignore the negative hotrock signals as they’re easy to recognize. All other decent strength positive signals should be checked on the target ID meter, followed by a quick groundgrab and observe what happens to the ground balance readout over various targets prior to disturbing the ground with digging. All weaker signals should be investigated until satisfied about target ID, and that normally means digging the target signal… as I’m sure we all realize.

We have found that ground-grabbed rusty iron invariably falls to more conductive ground phase values, some of the prevalent conductive minerals here do the same, including pyrrhotite, cobalt and niccolite. Silver free from serious contamination of these mineral types normally does not change much or at all… especially the smaller sub-gram silver, and I imagine gold responds similarly. But don’t force the issue, and by that I mean don’t pump the coil more than five times because that is more than sufficient for the internal computer to categorize the target. No technique is infallible of course, but the GROUNDGRAB / FASTGRAB feature available on modern prospecting-capable units does offer some additional target ID information. One other thing, concentric coils are more effective for this type of target evaluation because the positive signal of non-ferrous targets is more likely to remain intact after using the groundgrab feature. For detailed reading on this topic you may wish to view the last section at the link below. http://www.treasurenet.com/forums/canada/328287-electronic-prospecting-silver-country-part-2-a.html

As a point of interest, if you plant test targets to make relative depth comparisons, you will see distinct differences in detection depth comparing DE / PF modes to the JE mode if even minimal iron discrimination is employed. At least that is the case here, and it is a nuance you should be aware of. Any coin size non-ferrous target buried beyond five or six inches will read as iron, will invariably target ID at “14”, and that will remain the case for many years here. Under these circumstances, JE mode produces superior depth over all such targets. This nuance is something to keep in mind if searching in loose or unconsolidated tailings, or any application that involves searching disturbed ground… for example urban renewal projects where material is moved around. Otherwise I suppose the most likely alternative is to employ zero discrimination in concert with 2F iron tones… but check out those deeper iron signals… especially those that target ID at “14” that may in fact be non-ferrous.

With any luck we’ll be in touch over the course of the coming months to see how things are progressing. I hope to hear that you’ve had some good results in the field… all the very best with everything. :)

Jim.
 

 

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Hi Jim,

 

Thank you for another excellent informative post.  Thanks for adding photo as well.  I hope to find some silver one of these days.  Not too much found locally but I'm not too awfully far from places that produced large quantities.  I have heard of a couple platinum finds locally as well.  The validity of some of the finds is unknown but it is possible for sure.  Heard tell of an 18 oz pocket of platinum not far from here.

 

In the short amount of time I have used the F75, it does seem that of all of the discrimination modes, the JE mode works the best for me in high mineral dirt.  It seems to allow a quicker sweep speed and maybe a little better depth than boost mode.  I haven't thoroughly played with all of the modes but I find your description/comparison of the modes to be exactly what I am seeing as well.  Once I can learn what the detector is trying to tell me in disc modes, I will try and figure out the all metal mode.

 

I'm really happy I finally purchased the F75.  Steve's posts back on the old AMDS forum originally peaked my interests.  Reading your adventures intrigued me even more.  In the past couple years I broke into the coin/relic scene when I purchased the AT Gold.  I was only detecting for nuggets prior to that.  I originally purchased the AT to detect old cabin sites in the mining areas.  Something the prospecting specific orientated machines are not well suited for as you know.  Once the AT got me hooked, I knew I had to have the F75.  This new one with DST really is a pleasure to use.

 

I have not had the opportunity to try a concentric coil on the F75.  My interest is once again peaked :-)  My go to coil at the moment is the 5 x 10 DD.  I feel the performance in mineralized soil and trashy sites to work better for me than the stock 11" coil.  I also prefer the solid design, doesn't hang up on every little twig.

 

Unfortunately, I don't see any detecting time in my near future.  Life is getting in the way :-(  But I can't wait to get out and continue my F75 education.

 

Thanks again for the excellent information.  I will print it out and add it to my F75 bible that I have created from all over the internet.

 

Kenny

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