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People often forget about factory reset functions since it is still a rare feature. I am a proponent of resetting newer generation digital metal detectors on a regular basis, especially if settings get changed around a lot. The more setting changes are made, the more chance of a programming bug slipping in and messing with the operator. This is the procedure for the many F75 variants out there.

From the F75 Owner's Manual page 10:

RESET function
The F75’s microprocessor saves all settings which you input, even after the power is turned off. If you wish to reset the settings to the factory preset, follow this process:

  1. Turn detector off.
  2. Press-and-hold the red MENU button and push-forward-and-hold the TOGGLE SWITCH.
  3. Turn the detector on, while you are still holding the controls.
  4. Release the MENU button and TOGGLE SWITCH.
  5. See the F symbol. When the F disappears, the detector is reset. Note: some latest F75 versions may show five pairs of number instead before displaying the F - the ten digit serial number.
  6. All settings have now been returned to factory defaults.

fisher-f75-plus-ltd-se-metal-detector.jp
Fisher F75 Metal Detector

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That's similar to the factory reset on the T2,  There are a lot of rumours floating around it never needs a reset and the reset procedure is the same as the F75. I do it after changing coils on it, not sure if I'm meant to but it seems the right thing to do.  It's seems its a misconception that the T2 factory resets every time it's turned on.  I've read about people doing factory resets on T2's and it fixing issues they've been having.  To factory reset a T2 you hold the menu button down while holding the trigger forward and it will reset.

 

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Well, the T2 has no ability to save settings, and so it does come on in factory default settings every time you power up. That is not the same as doing a factory reset however, and so while you will not see any settings revert on the T2 when doing a factory reset it is still not a bad idea.

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Excellent/useful reminder Steve!

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The F75+ is a different detector, an updated version of the F75 referenced in the original post. The reset function was changed to incorporate the new DST feature. From page 10 in the Fisher F75 Ltd DST | F75+ User Guide:

RESET function
The F75’s microprocessor saves all settings which you input, even after the power is
turned off.
If you wish to reset the settings to the factory preset, follow this process:

  • 1. Turn detector off.
  • 2. Press-and-hold the red MENU button and push-forward-and-hold the TOGGLE SWITCH.
  • 3. Turn the detector on, while you are still holding the controls. At this step, you can turn DST on or off (see pg. 16 instructions)
  • 4. Release the Menu button and Toggle Switch. Screen will display 5 pairs of numbers (10-digit serial number), followed by “LE”. When LE disappears, the detector is reset.

and then from page 16:

The user may choose to operate with DST or without DST.
The default setting, at power-on, employs DST
To turn DST OFF, perform the following:

  1. Turn detector off.
  2. Press-and-hold the red MENU button and push-forward-and-hold the TOGGLE SWITCH.
  3. Turn the detector on, while you are still holding the controls.
  4. Continue to hold the controls.
  5. See the "90" displayed.
  6. Rotate SETTINGS KNOB clockwise.
  7. See "91" displayed.
  8. Release the MENU button and TOGGLE SWITCH.

Upon release of the controls, the detector will operate WITHOUT DST

DST status is saved to memory after the user performs this procedure.
Each time the detector is powered back on, it will continue in the programmed setting.
The same procedure is used to turn DST back on, except that the SETTING KNOB is turned counterclockwise to change "91" to "90".
DST can be turned on or off as desired, but each change requires the user to first power the detector off.

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I figured with the new change I was doing it right. I saw where to change DST on, and off. I’ve just left it on. Last time I reset it, the detector became a lot calmer, and more stable, but yesterday didn’t change much.

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Since I am somewhat new to the F75LTD DST/F75+ I have done several resets which have gone just like Steve's last post. First I get either 90 or 91 then after releasing the toggle and menu button I get the serial number and start-up concludes.

I have been puzzled by the DST On and DST Off settings stated in the manual and have done a lot of research including the findings of Keith Southern and Tom Dankowski. At least for me in my EMI overloaded area, the 91 setting (supposed to be DST Off) is way quieter than the 90 setting (supposed to be DST On). In my backyard, which has rendered numerous famous detectors absolutely incapable of operating due to EMI (impossible to hear a real target for all of the chatter) I can run my F75LTD DST at 80 sensitivity in any setting or process including All Metal when set to 91. If I set it to 90 I might be able to hear my test garden targets if I turn the sensitivity down to 20 or 30. So, who knows........

Jeff

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The explanation in the manual and the arbitrary numbers are such that it would be easy for them to have got it backwards. One would assume whichever setting is quieter has DST engaged.

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14 hours ago, Steve Herschbach said:

The explanation in the manual and the arbitrary numbers are such that it would be easy for them to have got it backwards. One would assume whichever setting is quieter has DST engaged.

So in essence the 90-91 could be backwards? Or at least a possibility? I’ve never personally changed them so I don’t know yet, I do know the other day when I reset it all settings went to factory, and it was a lot quieter, but I also may have switched 90 to 91 without realizing it

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    • By Steve Herschbach
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    • By Herbert
      Hi all,
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    • By Steve Herschbach
      Once upon a time all metal detectors went beep, and you dug up a metal object. Then a simple form of discrimination was developed based roughly on the conductivity scale. The main feature of this scale is that ferrous (iron or steel) items read lower on the scale than non-ferrous items. In a perfect world all ferrous readings could be set as a negative number, and all non-ferrous items set as a positive number.
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      Those who chase these low end targets run into another problem with ferrous. Very small gold, lead, aluminum, and other small non-ferrous low conductors actually overlap with small ferrous items and so the clean ferrous to non-ferrous "breakpoint" does not actually exist,. The breakpoint is more of a "breakzone" i.e. a fuzzy zone where items overlap. The ground itself contains ferrous materials in the form of iron minerals. Ground minerals can act to confuse the detector further, enhancing the chance that a small non-ferrous reading will be interpreted as ferrous. Another way to say that is that in highly mineralized ground the overlap between ferrous and non-ferrous targets gets larger. The ground mineralization is critical to how this all works and so air testing is not recommended for testing the ferrous/non-ferrous overlap region on any particular detector.
      Note that this does not apply just to very small items. The deeper an item is, the smaller it appears to a detector. In other words a deep large item can sound just like a shallow small item. When you bury items of any size in highly iron mineralized ground, the deeper they are, the more chance the ground mineral signal will overlap and cause the item to read as ferrous right at the edge of detection range.

      Fisher F75 metal detector
      The early model discrimination detectors usually had a knob that adjusted all the discrimination. Everything below the knob setting was ignored, and everything above the setting accepted. The discrimination pioneers rapidly discovered that the dividing line between ferrous and non-ferrous is "fuzzy". The knobs could be set to reject nearly all ferrous readings, but then some good non-ferrous targets would get missed. The solution was to use a little bit lower discrimination setting, which meant more ferrous trash was dug, but more non-ferrous items were revealed.
      Managing the ferrous to non-ferrous breakpoint is critical. There is no setting that rejects all ferrous while detecting all non-ferrous, and the more mineralized the ground is, the less reliable the settings become. As a rule of thumb, the more aggressive the iron rejection, the more chance of non-ferrous items being misidentified.
      Detector technology advanced, and tone schemes were developed that divide the discrimination scale up into segments or "bins" where all numbers within a specific range make a specific tone. These tone schemes are often preset at the factory. The ranges can be arbitrary and arranged in many ways, but all share one common factor. Where is the setting that divides low ferrous tones from the higher non-ferrous tones? This is the "ferrous breakpoint". Everything below this point will give a "ferrous tone" and everything higher a "non-ferrous tone".
      The detector engineers are well aware of the overlap between ferrous and non-ferrous items. In choosing one setting to define what is in reality a zone the engineers have to make a hard choice. If the setting is too low, the operator will get many non-ferrous readings that turn out to be ferrous. That really irritates people. Or they can set the breakpoint higher. That way less ferrous gets dug. Some good non-ferrous items will also be missed, but only in the rarest cases does anyone ever know what they are missing. The odds are there will be more complaints if the ferrous breakpoint is too low than too high. The goal is not to find every non-ferrous item, but to keep from digging too much trash identified as good.
      This diagram is shows the common discrimination range employed in nearly all metal detectors. This particular model (Garrett) sets 40 as the point where ferrous items separate from non-ferrous items. Yet the chart reveals the overlap zone runs from about 35 to 45, a solid ten point spread. Small gold can identify as ferrous, especially in iron mineralized ground. Many detectors identify this zone on the meter via overlapping diagonal lines.

      The ferrous/non-ferrous overlap region
      What this means is that any detector that employs a preset tone scheme with no ability to adjust the "ferrous tone breakpoint" is assured to be missing at least some items due to an overly aggressive setting dialed in at the factory. This was eventually recognized, and now quite a few detectors allow the point where ferrous tones flip to non-ferrous tones to be adjusted. Some models are now even allowing for multiple volume controls for each separate tone, are at least the ferrous tone. This is most often called a "ferrous volume" setting.
      The Fisher F75 is an earlier tone based model and as such the tone schemes are preset at the factory. You can choose between the schemes, but the tone settings of where the tones occur cannot be adjusted. The F75 employs a target id scale that ranges from 1 to 99 with the 0 - 15 range defined as ferrous. From the F75 Users Manual page 20:
      1. 1-7 iron
      2. 8-15 iron
      3. 16-20 foil
      4. 21-25 foil
      5. 26-30 nickel
      6. 31-35 nickel
      7. 36-45 tab
      8. 46-55 tab
      9. 56-60 zinc
      10. 61-65 zinc
      and from page 25:
      F75 OBJECT AND TARGET I.D.
      Most iron objects 4-12
      foil from gum wrapper 16-25
      U.S. nickel (5¢ coin) typically 30
      aluminum pull-tab 33-55
      aluminum screw cap 60 - 70
      zinc penny (dated after 1982) typically 60
      aluminum soda pop can most often 63-69,
      but can vary widely
      copper penny, clad dime typically 70
      U.S. quarter (25¢ coin), clad typically 80
      50¢ coin, modern clad typically 86
      old silver dollar coin typically 90
      US silver Eagle $1 coin typically 91
      The implication is that non-ferrous items will only read 16 and above. Any readings of 15 and lower are deemed ferrous.
      The F75 has several preset tone schemes, the basics being monotone, two tone, three tone, four tone, and Delta Pitch (separate tone for each target id number i.e. multitone).
      The quirk is simple. The two, three, and four tone schemes all have a non-adjustable factory preset low tone for ferrous at 15 and below. The tone schemes override any other discriminations settings. In other words, if you have manually set the discrimination for ferrous to be a lower setting, switching to any two, three, or four tone scheme will automatically change the low tone setting to be at 15 and lower.
      The problem is that with time it was revealed that the F75 will detect some non-ferrous items at much lower settings than 16. Tom Dankowski finally put it all together and determined that a reading of 7 or higher would reveal additional non-ferrous items that are rejected when the setting is at 15. Tom's recommendation for the F75 while hunting ferrous is therefore to not use the tones, but to use the monotone setting and adjust the discrimination manually to 6. That way items 7 and higher signal as a non-ferrous target instead of delivering a low ferrous tone via the tone schemes. Again, going to a tone setting will automatically override a manual discrimination setting if one has been set.
      Tom wrote this all up as a great article in the 2009 Fisher Labs World Treasure News on page 11.
      I actually had the chance to see this in person in my own use of the F75. Early on I trusted the tone settings and two tone is quite handy for those simply wanting to dig all non-ferrous. Yet on my trip to England with the F75 I encountered a mystery. A gold coin was found and another F75 newbie was telling me about how he tested it with his F75 and it gave a nice ferrous tone. He was quite upset and worried his detector was defective. He did not have the coin however and so I could not see what he was describing and at the time I have to admit I was clueless. I know now that he was using tones, and that the gold coin was reading lower than 16 and so being identified as ferrous!
      My early use of the F75 was more for gold nuggets, and I usually used all metal mode. Yet my favorite feature on the F75 was full time target id while in all metal mode. My method was to acquire all targets, then dig any that flickered even once above my mental ferrous breakpoint. Unfortunately I leaned too much on the user manual initially and tended to pass on targets reading under 16. My early writing on the subject reflected that. After I discovered on my own that gold was reading lower I started adjusting my mental settings lower. Then I bumped into Tom's writing on the subject and it all came together.
      The bottom line in that non-ferrous items can read as low as 7 on the F75 yet the ferrous tone break is set at 15. This is just fine for most Park coin detecting, but problematic for those hunting low conductors of any sort or coins in dense ferrous. Either use monotone and decide where you want the setting to be (6 as Tom recommends or maybe somewhere in between 6 and 15 if 6 has you digging too much trash) or hunt in all metal and use the target id numbers to decide when to dig keeping in mind non-ferrous can read lower than 16, especially in high mineral ground.
      This is not a flaw in the F75 but just a function of any detector using a preset tone scheme. There are many detectors like this on the market. They tend to be less expensive models, or older models, as most new detectors now feature an adjustable tone break for the ferrous/non-ferrous overlap zone.
      Another take on the subject.
      And down the rabbit hole - Tune Out Nails - You Will Miss Gold!
      Fisher F75 Information Page
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