Fisher 1265 Revival

[ivconic]

Funny!? I thought my last post will provoke quite interesting discussion here..? Yet nothing happened?
Everybody are just in a sort of "fever rush" to get or make some new detector, yet nobody really showed any interest for present problem i explained in previous post?
For what are good new detectors or handmades if can not overcome the existing problem? It is easy to buy or make descent IB detector.Not an issue. But what than...take it outdoor and skip many gold and silver coins due fact those were covered with roman clay,hot rocks or black sand..or some ancient ceramic rich with minerals etc..etc...
I had oportunity (sort of luck) to test all the major models on market today.
I would not make a full list with details (no need for it) but generally, almost all models showed more or less laxity in explained conditions.
Major models like Explorer or Garrett GTI2500 or newest Fisher serie or even DXF serie...ha,ha,ha...strange and deterrent fact - at certain conditions those are not accurate at all, even at lowest depths like 10cm in the ground!!

[ivconic]

Also would be good if all of you can obtain (for your testings and experiments) a piece of roman clay - an potsherd actually (a piece of it) ...let's say 10x10cmx4cm.
What amazed me is the fact that simillar piece could actually affect phase and amplitude more significantly than ordinary ferrite - in different manner!? Wow! So when detector adjusted just about to totally reject that material i know for sure it is ready for going outdoor and also i am sure i will not catch any falses even on hardly mineralized soils.


Now... i will suggest here a very good test for you;
take a suggested piece of potsherd and put over 1e coin to completelly cover the coin. Now try to detect coin cleary. Ha,ha,ha!!!
Than remove clay and again test detection on coin only. Detector will detect coin pretty accurate and cleary. Than with same adjustments on device, cover coin again with potsherd piece and swing coil over it. In best case coin will be bairly detected and reported as..... iron!?
Most of original metal detectors i tested recently showed pretty disapointing performances. 80% of them never detected coin under potsherd piece. 15% of those detected it but reported as 100% iron!
Only few of models detected coin accuratelly with a slice decayed signal and reported it as "coloured" item. I must say TGSL was between those few models, although TGSL lost depth on coin and detected it just on 60% of distance then it was on bare coin without ceramic over it.
I laughed much few days ago when tested Minelab Explorer II on this; coin was detected just good in air, but later when covered with single piece of potsherd ..... no detection at all!? Ceramic potsherd piece was 4cm high...so it means Explorer II didnt detected 1e coin at 5cm distance!?
Spectrum detected it with pretty confusing VDI behavior and mumbling sound. Fisher CZ7 Pro reported it as 100% iron...etc...etc...
So...looking at this, i am wandering how, the heck, much gold and silver coins i skipped so far??? How many other nice items?
Cose...i dont know about your situation, but here at my place we usually do visiting terrains rich with ruins and millions of potsherd pieces along with other simillar ancient ceramic scrap as well as much of the hotrocks and black sand too.
So...just perform this test and see with your own eyes - you will be more than disapointed. You will start asking yourself much questions than...

[Qiaozhi]

Actually no need to totally reject ferrite at all. Medium soil has much less influence on amplitude and phase than ferrite itself.

That is a very good point, and worth bearing in mind.

[ivconic]

I agree with Quiaozhi.
I also noticed that it is not possible to totally reject ferrite when Disc is set to minimum..i guess it is normal at 1265.
Quite oposite than at TGSL, where ferrite can be rejected totally even in All Metal mode. Both ways are normal due different approach to those 2 designs.
But at 1265, later is easy to reject it totally with Disc set to some higher level, usually over "2".
Actually no need to totally reject ferrite at all. Medium soil has much less influence on amplitude and phase than ferrite itself.

[Qiaozhi]

I am not the expert on this question. Maybe qiaozhi could pipe in here. I think that he has more practical experience in this. I believe it would depend on the size of the antenna core. What I used was a section of a ferrite core emi filter ~1/4 inch square section ~1 1/2 inch long. That may be larger than what should be used.

In theory the size of the ferrite should not matter, as it produces amplitude changes, and no phase-shift. However, this is only true if you are sampling exactly on the zero-crossing point. In practice the GEB setting is usually offset by about -5 degrees to compensate for slight mineralization, and therefore the larger ferrite gives a louder response than using a tuning slug. For larger ferrite test pieces you need to increase the distance from the coil accordingly.
Fisher's engineers use a ferrite tuning wand, which is basically a stick with the ferrite slug glued on the end.

[KingJL]

Does this ferrite need to be very specific?
Can I use a ferrite core from an old AM radio antenna for calibrating?

I am not the expert on this question. Maybe qiaozhi could pipe in here. I think that he has more practical experience in this. I believe it would depend on the size of the antenna core. What I used was a section of a ferrite core emi filter ~1/4 inch square section ~1 1/2 inch long. That may be larger than what should be used.

[kt315]

20mm=2cm~2,54cm=1 inch

[Tinkerer]

Calibrating Ferrite

Does this ferrite need to be very specific?
Can I use a ferrite core from an old AM radio antenna for calibrating?

Your test results look excellent when compared to other test results posted on the forum. Congratulations.

Tinkerer

[Qiaozhi]

I finally obtained a sample of ferrite to complete the 1265X setup (specifically to set the GEB). First I carefully re-peated the setting of the Disc Bias, Threshhold, and Static Threshold controls. I then adjusted the GEB until it would detect the ferrite at 2.5-3 inches.

Retested "in air" detection distances and measured the following: nickel at 27cm, mens wedding band at 33cm, US clad quarter at 33cm, US clad dime at 31cm. These detection distances were performed with the following settings: DISC1 at 4, DISC2 at 5.8, Vol fully CW, Sensitivity at 3 o'clock (just barely quiet without target, very occaisional random noise). One thing that I noticed is that Static mode (all metal) is not nearly as sensitive as the Disc (normal) mode. Looking at the schematic, I can somewhat understand this as the Static channel has much less gain than the 'motion channels'.

Regards,
J. L. King

According to the manual, you should get a good target response with a copper penny at approximately 8" (i.e. ~20mm) in static mode with Sens at 3 o'clock in max sens.
Also, with Disc 1 and 2 at '10', and Sens at 3 o'clock in max mode, you should get a penny at a height of 9" (i.e. ~ 23mm) at moderate speed. The result should be a faint, clear audio response.
I think you're good to go...

[KingJL]

Let's try this again! Re-assemble the case and try to slip in PCB assembly. This time everything fits... barely! Power on and recheck everything. It works. This thing is surprisingly sensitive for a unit with a 8 1/2" coil. A mans wedding band at 26cm, a nickel at 25cm, a dime at 24 cm, a quarter at 28cm.

I finally obtained a sample of ferrite to complete the 1265X setup (specifically to set the GEB). First I carefully re-peated the setting of the Disc Bias, Threshhold, and Static Threshold controls. I then adjusted the GEB until it would detect the ferrite at 2.5-3 inches.

Retested "in air" detection distances and measured the following: nickel at 27cm, mens wedding band at 33cm, US clad quarter at 33cm, US clad dime at 31cm. These detection distances were performed with the following settings: DISC1 at 4, DISC2 at 5.8, Vol fully CW, Sensitivity at 3 o'clock (just barely quiet without target, very occaisional random noise). One thing that I noticed is that Static mode (all metal) is not nearly as sensitive as the Disc (normal) mode. Looking at the schematic, I can somewhat understand this as the Static channel has much less gain than the 'motion channels'.

Regards,
J. L. King

[skypilot02]

Many Thanks!! I've been looking for a switch for my 1266 for nearly a year!! Good luck and great hunting!! Regards, Richard.

[KingJL]

KingJL, skypilot02 here! I see that you live in Greenback,TN. I live in Tellico Plains, just down the road!! Found a lot of silver and wheats (plus some V and Buffalo and War nickles) at the old house that stood near the corner by the old store on 411. I see there's a Family Dollar there now.

Will send you a PM about locality/local info.

By the way, what did you use for the sensitivity switch on your '65? I have a weak one on one of my '66's, and need to replace it.

I ordered a 100K pot w/PNP switch from Mouser. P/N: RV16BF-10-15R1-B100K; Mouser P/N 313-1601F-100k. But, be forewared it is a very tight fit; In fact will not fit without some modifications to the bracket and bracket bolt (bot inside the conrol box case).

Regards,
J. L. King

[skypilot02]

KingJL, skypilot02 here! I see that you live in Greenback,TN. I live in Tellico Plains, just down the road!! Found a lot of silver and wheats (plus some V and Buffalo and War nickles) at the old house that stood near the corner by the old store on 411. I see there's a Family Dollar there now. By the way, what did you use for the sensitivity switch on your '65? I have a weak one on one of my '66's, and need to replace it. Thanks ahead of time for any help you feel like offering! Regards, skypilot02, (Richard).

[KingJL]

.... I am missing a metric nut for the Mode switch!!! I need to go to Ace hardware tommorow to try and locate a nut that fits.

I believe that that nut is the only thing that stands in the way for a completed revival!

Well, almost. Could not find a nut that would fit! I finally got a 3/16 nylon nut, drilled it out with 7/32, drilled 15/64 starter area (about 1/4 the way through), and threaded it on the switch. It works!

Now to slide in the PCB assembly. Oh no! There is interference between the aluminum channel case mounting bracket and the replacement sensitivity control. Out to the workshop and modify the aluminum channel mounting bracket; Also grind about a 3rd off of the head of the mounting bracket bolt.

Let's try this again! Re-assemble the case and try to slip in PCB assembly. This time everything fits... barely! Power on and recheck everything. It works. This thing is surprisingly sensitive for a unit with a 8 1/2" coil. A mans wedding band at 26cm, a nickel at 25cm, a dime at 24 cm, a quarter at 28cm.

Revival complete!!!!

[Qiaozhi]

Well, the parts arrived at about 1 PM today. Got to work replacing potentiometers. Had to substitute for the Sensitivity control; A tight fit but got it to work. Connected the ribbon header to the header socket; Connected 10.3 voilts to the off/on switch and powered the beast up. I have sound!!

Went through the setup procedures that Qiaozhi wa kind enough to provide. Something not right! I can detect a dime and a quarter, nothing else. All metal/pinpoit mode works OK. Disconnectect ribbon cable and coil, re-inspect board. Just for grins, I give it a good brushing with my soft paintbrush. Take the shell off of the coil cable connector. Lots of rust (remember hurricane Ike)! I clean all the rust and re-assemble coil cable; Re-connect the ribbon cable header and power up. We have working metal detector!! Disc1 and Disc2 functioning properly.

Now to re-assemble all the peices into the housing. I am missing a metric nut for the Mode switch!!! I need to go to Ace hardware tommorow to try and locate a nut that fits.

I believe that that nut is the only thing that stands in the way for a completed revival!

Very good news. No doubt a satisfying result.