Erratic 900 Nox

[D&P-OR]

6 hours ago, Chase Goldman said:

If ML repair is ultimately saying nothing is wrong with your detectors or coils, one thing you both can do is dial back on the 900's sensitivity setting.  It clearly runs a lot more hot than Nox 800, and that combined with less Target ID stability associated with the expanded TID scale means you should probably run the 900 at a sensitivity setting of 20 or less for most situations for stability.  I would dial down sensitivity until the instability abates, and note that setting.  If it falls somewhere in the range of 15 to 20, go with it. If it is much lower than that, then I would say that your best bet is to make a video of what you are seeing and to show that it happens on multiple coils and at low sensitivity settings if that is indeed the case...HTH and Good Luck.

Excellent advice.

[jerrym]

On 12/4/2023 at 3:23 PM, jerrym said:

 

Will do waiting to hear from the repair shop

Minelab said the detector and coils were fine, I took it and had the same problems.  I ran the recovery speed and iron bias up and down and also used individual frequencies. It acted the same way chattering and vid signals were all over the place.  Never has this problem with my nox 800.  I returned the 900 back to Kellyco and debating whether to get another 800 or a nokta legend.

[Zaj56]

5 hours ago, jerrym said:

Minelab said the detector and coils were fine, I took it and had the same problems.  I ran the recovery speed and iron bias up and down and also used individual frequencies. It acted the same way chattering and vid signals were all over the place.  Never has this problem with my nox 800.  I returned the 900 back to Kellyco and debating whether to get another 800 or a nokta legend.

That sure sucks! When my 900 acts up again I'm going to video it  for sure and like you...never had this problem with my Nox 600

[mcole]

I am having the exact same problem with the larger stock coil for 900. Turn it on and chattering is an understatement.  Machine is rendered useless and vdi running all the way up and down the scale. Adjusting settings is no help as recommended by other posters - worked on this in the field for 30min.

I have not yet decided what to do.

But using the 6" coil later today.

[Zaj56]

 I sure hope we can solve this mystery. I had posted earlier that I had dropped my coil off at the Minelab repair center and they did a bunch of tests on it and said it was perfectly fine. I haven't had the issue since..fingers crossed

[HardPack]

5 hours ago, mcole said:

I have not yet decided what to do

Both the 11” & 6” Nox coils run stable on my EQX 900. The 10x5 Coiltek is more sensitive to EMI and ground noise. In my experience turning down the sensitivity to 18 or even 16 does not affect detection depth all that much with ground balancing in the 40 range. At the lower sensitivity settings the erratic TID spread also settles down. Also, if not needed, I set recovery to 1 and Iron Bias to 0, Discrimination setting of -19 to -10 reduce ground noise plus allows detection of ferrous suppressed TID’s of non-ferrous targets. Such as gold that is pulled down into the shallow negatives by adjacent iron trash or highly mineralized soil.

Prove it to yourself, buried a sequence of coins (1, 5, 10, 25, etc) in your dirt at different depths (5”,6”, 7”, 8”, etc) then play with the 900 settings. Work the solution, you may be surprised.

[Digalicious]

21 minutes ago, HardPack said:

 In my experience turning down the sensitivity to 18 or even 16 does not affect detection depth all that much.

Are you sure about that Hardpack? How much is "not much depth loss"? 🙂

Have you done comparisons depth tests between maximum or near maximum sensitivity, and 16?

[HardPack]

24 minutes ago, Digalicious said:

Have you done comparisons depth tests between maximum or near maximum sensitivity, and 16?

Check out the post in “Metal Detector Advice & Comparisons” under the topic “EQX 900 & Legend Separation”; on the top of page 2. Chase may be on to something. 
 

[Digalicious]

4 minutes ago, HardPack said:

Check out “Metal Detector Advice & Comparisons” under topic “EQX 900 & Legend Separation”. Chase may be on to something.

Thanks. I'm heading out for the day, so I'll check that out later.

On my Legend, there is a 4" depth difference between 16 and the maximum setting of 30. I could be completely wrong, but I suspect that a similar sensitivity depth reduction would result in a similar depth reduction on the 900. 

[HardPack]

2 hours ago, Digalicious said:

On my Legend, there is a 4" depth difference between 16 and the maximum setting of 30. I could be completely wrong, but I suspect that a similar sensitivity depth reduction would result in a similar depth reduction on the 900. 

I was using the 11” Nox coil in the “Separation” post. I was attempting to arrive at a stable baseline detection depth for the EQX 900 in a specific soil type GB 40. I started with the Sensitivity setting adjustments with Recovery 1 & IB 0. Then to get a feel for recovery setting adjustments impact of depth with Iron Bias at 0, Sensitivity 18. Then a separate run over the buried coins adjusting Iron Bias settings with Recovery at 1, Sensitivity 18.  

At the actual detection site the soil type differs with a ground balance of 30 (isolated areas at 54), has ground noise plus an overlaying carpet of buried rusted tin and major EMI. On this specific site the recovery & iron bias setting are headed up in order to cut down through the buried ferrous trash in search of deeper non-ferrous targets. This is driving the need for the ferrous/ non-ferrous target separation. Prior on site use of the coils with EMI demonstrated the stock Nox coils were more stable than the coiltek. How much depth will actually be lost, this portion is still a work in progress. I would suspect in higher mineralized soil types sensitivity adjustments would have a proportional impact on detection depth…