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

[detectoman]

wow, what bad is my english!

[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]

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

[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.

[Funfinder]

Thanx, ya welcome.

[detectoman]

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

[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]

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]

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.

[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]

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]

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]

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]

Wow, that was really a good explanation! Thank you!

Of course: nano!

Seems around 40-60 nF in total would work best.

But anyway, we can use already the cutoff-frequency for eliminating more or less disturbing interference with best sensibility.

The Fisher is no longer an Electro-Smog Detector!

[Qiaozhi]

I've done it!

Back to almost full bias without noise!

Depth gain: 50% !!!
Ring: 10cm before & 15cm after mod.

Disc Bias variable R. 325 still tunable.

Only 1 small 10 pF condenser needed.
Soldering very easily on smooth side.

Conclusion: The already in use C311
with 22 pF should have 10 pF more.

Schematic with modification is here:

http://www.multiupload.com/24F4VVEKZQ

Hi Funfinder,

By changing the capacitor value in the feedback loop you are modifying the cutoff frequency of the second-derivative filter. However, you stated in the text that you have added only 10pF more capacitance, and that the original capacitor value was 22pF. In fact, the original capacitor value was 22nF (0.022uF), and according to your photo of the PCB, you have actually fitted a 100nF (104) cap.

This means the original cutoff frequency was 7.2Hz, and you have lowered this to 1.3Hz.