BandidoII DISC phase shifter LOOK at this!

[Northerntrowel]

For those peoples that build the BandidoII from original Carl schematic with original cap. value and a real Tesoro coil!
Any one of you can try this little mod for me? (Or for yourself)
I make this mod on mine and that is sold my Strange DISC variation range!
But ! because i have changed the front-end amplifier,i cannot say that is the answer for the original shematic problem.
So! If you want to try it!?!
First pic= Original Disc shifter
Secon pic= My mod
If you take a look at the phase shifter from the "Golden umax" and from the "toltec 80" i take the mod from these shematic.

[Northerntrowel]

Fisrt and second pictures...

Original configuration
http://thunting.com/geotech/forums/a...1&d=1175254245

The moded configuration
http://thunting.com/geotech/forums/a...1&d=1175254355


Thanks!
JF

[Northerntrowel]

OOPS!

In my first message ...I meant:

I make this mod on mine and that resolved my strange DISC variation range problem.

O.K. now that's better.
Salut!
JF

[Northerntrowel]

Another thing!

Because i changed the front-end amplifier(White classicIII configuration instead of Tesoro umax) ,i had to change only one cap value to the Disc phase shifter.And my Bandido work fine now!
look to the attachement!...
If some one of you get positive results with this mod,please to share it here!
Thanks!
JF

[chemelec]

Because i changed the front-end amplifier(White classicIII configuration instead of Tesoro umax) ,i had to change only one cap value to the Disc phase shifter.And my Bandido work fine now!
look to the attachement!...
If some one of you get positive results with this mod,please to share it here!
Thanks!
JF

That 130 pF was found to be Incorrect LONG AGO.

Actually My Schematic uses a 22 pF Cap as I found this is Probably the Origional value on the Manufacturered units.
Drfinately Not 130pF or even 30pF.
Although 30pF is probably Close Enough.

[Northerntrowel]

Hi! Chemelec tank! for reply.

I know ,30 pf is near to 22pf with tolrence.

I Think i will remake another test with the original configuration and the 30 pf.

It will take few minute and i will report my results.

Thank again!
JF

[Northerntrowel]

Hi! Chemelec,you are right!...

...Probably i forgot 1 stage in the process.Sorry for the doubt. I obtained approximatively the same patern of discrimination with the 30 pf cap.The only difference with my mod is that i have an extended coin range up to the silver dollar.But all the coin range is a keeper range,so it's not very necessary.

O.K.! Thanks! for your Help !Chemelec
My Bandido work fine!
HH!
JF

[porkluvr]

You have uMax?

Hello, Northerntrowel.
If you have schematic to Golden uMax or Toltec 80 could you please post one or both here, show a hyperlink or even drop me an email? Thanks!

I think that if too high a value of C10 is used in the Bandito discriminator, then arises the possibility that large iron will be detected when fully CW, but I have no easy way to test that.

How is it that silver dollars weren't detected before? Seems like something wasn't right. My understanding of the discrimination circuit operation is very fuzzy, at best.

[Northerntrowel]

Hi! Porkluvr

By an extended range of dicrimination up to silver dollar, i mean that you can detect a silver dollar and reject silver quarter at full CW of the control pot.
That permit you to see the difference between 1c/10c,quarter,halfdollar and dollar.

And if you raise again the C10 value you can reject a silver dollar.Maybe that can permit to see the difference between big iron items and the rest.But i will have to make the test with a greater value for C10 to be sure it can be usable in real conditions.

For the toltec 80. it was posted by Merc
here is the link to the topic
http://thunting.com/geotech/forums/s...ghlight=toltec

For the Golden Umax i cannot find it now .I think it was originaly posted by KT315 ,i'm not sure.I cannot post my copy on the forum because the size, even if it is compressed.The zip files is 1.29 meg

Hope that help you !
JF

[Max]

Hi all,
I'm sure now that 130pF is wrong there as Gary stated. I found having 22pF is right to reproduce goodrat's diagrams for that part of the circuit.
Also with 22pF I get near-to-total iron disc as bandido II must have when in disc mode. Imbalances occourrs only when masses of iron or sheets of it are really close to coil then perturbating too much filed lines.
So I think that the magic number is 22 !

It's interesting the use of 100Kohm resistor to modify phase shift but I think that this way one can go easy out of disc for iron and then failing rejecting it.

I don't know if is a good idea to have 30pF there...maybe if you NT change cap to 22pF you don't need resistor but just original pot.

Now I'm happy with disc (values of caps are the goodrat's sets present in Gary's revised schematics) and just play with some depth gain...using DD coil design.

I've just realized a DD of 22cm diameter like this:
120 turns tx 0.30mm wire tuned to 10KHz
120 turns rx 0.30mm wire

Both are about 23ohm in resistance.

Used tape for first wrap...then mylar/al for shields (wrapped too) then again another winding with electrical tape.

I get 2eur coin at 30cm in disc mode...and 32 in all-metal...and that's fine for a 22cm coil ! Yes...I lose pinpointing...and have to deal with the DD sensitive area under overlappings...but wow it goes deeper than with concentric round 8''. DD was really easy to make for bandido using that data...and really effective!

Much less noise with mylar shields...just get a little down in frequency to 9.860Hz...but seems not a problem. Disc works fine and deep !

Best regards,
Max

[Northerntrowel]

Hello! Max

WoW !you have maid a realy good coil! I keep your post in my files.
When my bandidoII will be well tuned.I will be able to experiment with coil bulding.
What you mean by mylar shield.Dou you use some thing like a plastic/ aluminium foil.??

And ,can you tell me the type of target you can detect at fully CW discrimination!??

That is just to have an idea to ajust my detector!

Thanks!
JF

[chemelec]

Because i changed the front-end amplifier(White classicIII configuration instead of Tesoro umax) ,i had to change only one cap value to the Disc phase shifter.And my Bandido work fine now!
look to the attachement!...
If some one of you get positive results with this mod,please to share it here!
Thanks!
JF

Where did you get That Schematic From?

I Have never seen that Arrangement for R23.
All the Schematics I have seen, R23 is on the Output Pin of IC7B and Connected to R69, with the Center of the Disc Pot connected between R23 and R69.

Gary

[Northerntrowel]

Where did you get That Schematic From?

I Have never seen that Arrangement for R23.
All the Schematics I have seen, R23 is on the Output Pin of IC7B and Connected to R69, with the Center of the Disc Pot connected between R23 and R69.

Gary

Hello! Gary.

O.K. I know i maid my circuit test a little bit too fast ,and now i am sure your circuit and caps value are good.I tested it with my circuit and it work fine.

The shifter arrangment you can see is from the schematic of the Golden umax i got on the Geotech forum few months ago.All the resistor are the same.But the arrengment is different.I only wanted to try this circuit in my bandido for experiment.The conclusion is the difference is minor.

JF

[porkluvr]

Thanks

>>By an extended range of dicrimination up to silver dollar, i mean that you can detect a silver dollar and reject silver quarter at full CW of the control pot.

Wow ! That's being downright picky!

Thanks for the info, Northerntrowel - I'll get busy combining merc's pages.

Here's a new take on an old joke:
Doctor, WIll I be able to find SILVER DOLLARS after you've fixed my metal detector? Yes!!? Well that's good, because all I could find before was new pennies and trash!
(Ouch, corny)

[Max]

Hello! Max

WoW !you have maid a realy good coil! I keep your post in my files.
When my bandidoII will be well tuned.I will be able to experiment with coil bulding.
What you mean by mylar shield.Dou you use some thing like a plastic/ aluminium foil.??

And ,can you tell me the type of target you can detect at fully CW discrimination!??

That is just to have an idea to ajust my detector!

Thanks!
JF

Hi Northerntrowel,
I use mylar/al that is mylar (plastic) with aluminium over. Really thin and hi-conductive...wrapped just like aluminium foil...but instead of foil it's really thin and you haven't phase shift problems or overloading or every else big modify respect not-shielding coils. I get a down in frequency about 130-140 Hz and that's all...this is due to capacitance...cause I wounded mylar on top of tape and don't used a spacer (e.g. polietylene spiral) as dielectric spacer/adsorber.
Mylar is fine also for PI. I've realized 8uS coil for GS4 with teflon wire and mylar shield. Very good coil...low noise and good shielding. And little delay...but used plastic spacer between coil wound and shield there.

I'm still making test with disc...can't say for sure...what detects at fully CW...but for sure not iron...that's never detected but only in cases I've described already (big masses near..etc). I get good signals on zinc and copper and also gold (but gold at near fully CCW). I've european coins to test with...and they are well detected all---> some are made or copper alloys other with more complex mixtures. I get Aluminum too close to gold and reject ferrite rings.

What's important to me are depth and rejecting iron (and possibly bricks-ceramics but not so easy). I have first 2 now...then with ceramics have signals when 3-4 cm from coil that's not so good.

Anyone knows how to eliminate/minimize those brick signals ???
Any idea ??? Any special coil design ???

Any suggestion welcome.

Best regards,
Max