Noise-Reduction for Fisher 1266-X (evtl. 1270-X & 1236-X2)

[Funfinder]

Anti-Noise Modification 20nF

http://www.multiupload.com/H9EAOS5C19

After tests with 5, 10, 20 and 40 nF capacitors I found out that 20 nF works best.

That's the double amount as default and therefore reduces background noise for 50% by really good conditions concerning sensitivity and discrimination signals!

Work's like charm!


If possible for avoiding confusion someone please delete the 2 multiupload-links and 2 capacitor-pix above.

[Funfinder]

Here the exact solder-points inbetween (red <---> black) you can attach the additional 20nF capacitor or replace the orig. (-> blue <-) with a 40nF.

> reduces background noise for 50%

In technical terms thats true, but practically - compared with before - it will terminate noise to 100%, depending on the adjustable bias level, which then is still very good.


What we learn out of this?
A very small improve with: "electronic parts match together" can give a huge gain in overall performance!
The same way a MD and the person who uses it has to fit!

[Funfinder]

40nF Modification!

I buried the below objects in high mineralized ground at 43cm / 17inch.

At 30th march I tested the "plus 20 nF" mod there.
I did know exactly where it was so I could distinct a slighlty difference between "snap, crackle and pop" and detectors metal signal.

Because it was such an almost unhearable difference, yesterday I tested: "plus 40 nF".
Now the bias is even higher and the signal is well distinctable by almost no background noise!

So if you want to push your Fisher 1266-X to the max I recommend replacing at least the C311 with a 47nF or add 30-40nF instead only 20.


Finally a question:
I heard the 1266-Xs current is stabilized at 7 or 8 V.
Is there a way to tune that to ca. 9-10V? I'm shure the electronic-parts will survive this but it could bring more depth again! Because battery-life is very good (around 30-50h) anyway, a bit faster power-drain is no problem.

[Funfinder]

No pix or schematics so far - just wanna inform you about the extended Noise-Reduction mod:


There is a push-pull knob vary. resistor for heavy mineralization / maximum sensitivity.

I found out that the push just switches to a ca. 100k / very high resistor.

So I cut that "crap", desoldered this formerly "max sens. circuit" completly and connected it with two 10cm cables onto the bias-variable resistor! It is ajusted around the middle, 90 of 180° or 50%.

For best results a 22k resistor inbetween one cable connects both var. resistors. It also works with 47k but the sensitivity range with this is smoother/closer.

Now this is the great achievment:

If the knob is pulled even at fully iron mode (disc at 1 out of 10) at lowest sensitivity there is no background noise at all. If sens is raised background noise slighly starts but if I turn the sens to 5-6, where I'm searching most of the time, the noise vanishes again and at disc level ten (silver or large objects) its gone again.

The pull selection is for high mineralised, trashy or electro-smog situations.

Now when I push the knob, the new modification shows his power. btw. the initial background idea was just to turn the bias-level without open the device.

If the sens knob is pushed at Disc Level 1 there is some background noise already, but very moderate and only if "disturbant signals" are near.

Now even at disc level 10 is some noise, but the same as before. But this is important to get the best depth results in areas with lower disturbance-factors.

If the button is pulled the first lower half of sensitivity is selectable, if pushed the upper half is accessible.

The pinpointing threshold function is not affected by this.
It is the same as before: No threshold noise at sensitivy Level low, but very good recognisable at 10.

In principle this pinpoint-function is a non-motion circuit on its on - no motion but also no metal-distinction. The sensitivity level for this circuit is adjustable by the little blue multiturn variable resistor nearby the bias one!

That much larger sensitivity range also gives better results in non-motion modus - ca. 20% more depth as before.


Now the 1266-X is super adjustable while hunting with much better target amplification at much lower noise level than ever before!

[Funfinder]

Today afternoon I've tested the mod out in the wild and it worked good. Found alot stuff as example a rotten gasmask from WW2 but also very small stuff.

Below two pix for better explanation:
That blue "doubleswitch"-var. resistor (used for the sensitivity-regulator) adjusts the output of a grey wire, going to the platine.

It's a bit complicated to deconnect this resistor so you also can just solder the cable to the board as shown below (red dots) and add a different variable resistor that is accessible from the outside.

Otherwise desolder the blue cable that is coming from the battery-check knob plus the single 100k resistor from the push-layer contacts which are located near the plain metal backside of the variable resistor and attach the both new cable-connections from the platine there.

[detectoman]

hello guys, my congratulations for modifications, friends; i like to make yours an question:
you think, may be i can make implement same modification? to my fisher 1225 x?
my md fisher is very efficient, excelent discrimination and respectable depth, is an very ok machine, work best in neutral soils, but in mountain, detect hot rocks or mineral
i understand what these machine x' are a bit same
any can help me?

[Funfinder]

Hi detectoman and thx ya for your interrest!

My Fisher also detects hot-rocks and minerals but this is no big problem:

Press the pinpoint-button by holding coil away from signaled target and if the threshold noise faints by getting near to that target it was mineralic or cavity.

My Mod just raises sensitivity and reduces background noise, but doesn't stops detecting mineralized rocks.

Discriminating this stuff would result in losing much depth, so just save yourself all the trouble and simply doublecheck with pinpoint.

[detectoman]

ok thanks my friend, i understand, you, point view, an embrace

[Funfinder]

Thanx, ya welcome.

[Funfinder]

Tweaking MDs really can make addicted - the both last days I did nothing else!

@ detectoman
This info goes in your direction:
I recognised the 12'' spider coil detects a little piece of rusty nail already as mineralisation, beyond the limits of the variable discrimination resistor (the one in the corner on the platine).

If you attach an 102 capacitor (1nF) parallel to (where) the RX coil wires (are soldered to the board) this kind of weak metal now also gets positive detected (ca. 4-8 cm distance) but also is discriminatable again at Disc Level 2 out of 10.

You can try this kind of modification with a bigger capacitor to discriminate little minerals but it will decrease the spectrum of the metal-disc-level.

[detectoman]

thanks funfinder, i look these fisher models are good machine, but extreme sensitive, so, put mineral detection, i interest in quit these propiertes of my fisher, due i cant use in mountain the fisher, but them in neutral soil are best, major what spectrum xlt, due xlt is out of combat in sun warm, then not discriminate to all, may be xlt is good for artic or rusia, not for desert, these is crazy
thanks, i apreciate any other modification for these stongerous machine md

[detectoman]

i had an fisher, also an xlt, an bounty hunter draw ll an outodoor spirit, an tracker, an mini garret bfo sistem of hig stability, an techna texas, an bfo made, of all the major is xlt, but in winter, these not detect mineral, and accept big plate blue, if fisher obtain mineral inmunity, then be superior to all, i had too, an detectron two box, of bulbes, too an two box made, not detect mineral, best whises for you
dman

[detectoman]

wow, what bad is my english!

[Funfinder]

Hi detectomen,

if I'll experimenting again with my Fisher and find a way to reduce mineralisation I will post the info here.

Because alot minerals are mixed with metal on a molucelar basis - quote from wiki "Aluminium":

>> Aluminium is too reactive chemically to occur in nature as a free metal. Instead, it is found combined in over 270 different minerals. <<

most detectors just do adjust the disc level to small iron objects and discriminate everything below.

The 1266x forwards the "raw" signals that's why you hear everything - even the discriminated metals often still "snap crackle and pop".

This is good to have the full control but also can drive you insane if the background noise reaches your own psycholgical threshold level. Thats why I modified it - sometimes I just want to have the detector to be quiet!

btw. detectoman - check out this thread:
http://forum.treasurenet.com/index.php?topic=166574.0

Very good and a huge amount of practical info about the 1266x from experienced treasure hunters.

btw. I found some 5cm / 2'' in diameter mineralized stones transported by an glacier at ice-age time 100km far away from the alps near to my village so I can make some tests. I'm also having bigger mineral-stones up to 5kg but I doubt the 1266x will ever remain silent over them, even at highest disc and lowest sens.


There would be a way to blend those signals out but this would need a complete different digital timing circuit. I wrote already about this possibility. Minerals create doubled audio output signals and if those additional circuit could detect it "live", it could be discriminated.

But because such a signal in total takes ca. 0,5seconds it would need a relative slow sweep and pace speed.

A better way would be to add some electronical parts so the coil gets completly overloaded by minerals so it outputs "out of range"-signals that no longer gets processed any further.

btw. I checked out already the "give a large beep"-circuit where the signal goes next after the bias-level. Its possible to "delete" those longer beeps but for a reasonable use more testing had to be done.


So far the best method to eliminate disturbing mineralic noise just is to add that 40nF capacitor and then trim the var. bias resistor to a level so the 1266x is as good as quiet at minimum sensitivity if minerals are near (at that discrimination level you like to search).

Just try it! Good targets no longer will get drown in a sea of "snap crackle and pop", even in mineralic areas.

[Funfinder]

Yesterday I had time to mod the 66 again - realizing a good new idea that really works:

a much larger sensitivity spectrum

The sens.-knob uses a 100k variable resistor which is in line with a second 100k, means a variarability from 100-200kOhm. This is fatal when you need a huge sensitivity-spectrum. You'll get a much broader one if that second 100k is replaced by a 10k - from absolutly no background noise to the most sensitivity.

Next I found out that it's possible to alter the still "saturated" electro-smog beeps, easy confusable with good target sounds into thinner ones by placing a 100k-1000k resistor into the audio-output stage.

And for even more powerful performance it's possible to interrupt the wire of those 560 Ohm resistor that shortcuts the receiving coil to ground directy where the incoming cable is soldered to the board.

But the most important is a real huge sensitivity range which doesn't exist by default and can make the trusty rusty 1266x almost worthless by too much and not deletable background noises.

Especially because the sensitivity changes with discrimination. While in all metal mode the background noise ist very high, at disc level 10 it is completly gone - but together with the maximum sensitivity! And if the usual sensitivity range is too small for re-adjusting all of this, first the MD loses depth and misses important targets, while second in iron mode too heavy background noise can render good signals worthless.

However, the best would have been Fisher had used from the beginning a circuit which is completly immune against all those electromagnetical influences. But even alot modern MDs from other brands still have the same problems.....