TESORO GOLDEN SABRE

[Max]

Thanks.
I think that have one.Will see.
And will tell you.

Nice. Then post the results...

[tiktak]

Hi

Hi,
Max.
Unfortunatly when I try to seal the coil it moovs and now I cant get the same performance!!I were geting 27cm for I euro coin with TL072 insteed of 353!!
And now cant get the same.
How did you null again Rx when shields are aplyed?
You told me that I have to null without shields!But when I shield them how you find that null again?
I were playing with both and just found a very good spot!
Sorry I dont have 3240.I have 3130 and 3140 ,but they are both single!
I will buy tomorrow 3240,but have to finish that coil,so can compare and be shore that I get the same coils position.
Thanks

[Max]

Hi all,
I've tested 2xLF351 instead of TL081 there... (first replacement for the old LM30 and things seem nice.
About the same, if not even better!

So good replacements with jfet inputs (tested) for LM308 here are now :
TL081
LF351

Problem is that 351, like 353 is obsolete now. So TL081 remain 1st choice,
cause it's really easy to find still today.

BUT ALSO (tested)
NE5534
OP07

seems fine there.

Think that for LF353 also LF412 or 442 could be fine. But don't tested yet.

At the moment my best performances are still with LF353!

Kind regards,
Max

[Max]

Hi,
Max.
Unfortunatly when I try to seal the coil it moovs and now I cant get the same performance!!I were geting 27cm for I euro coin with TL072 insteed of 353!!
And now cant get the same.
How did you null again Rx when shields are aplyed?
You told me that I have to null without shields!But when I shield them how you find that null again?
I were playing with both and just found a very good spot!
Sorry I dont have 3240.I have 3130 and 3140 ,but they are both single!
I will buy tomorrow 3240,but have to finish that coil,so can compare and be shore that I get the same coils position.
Thanks

Hi,
check the price first for 3240... seems that in some places it costs like GOLD in weight! Don't know why... maybe cause is sometimes hard to find and required by some costly apparatus (it's an instrumentation op. amp.).

"You told me that I have to null without shields!But when I shield them how you find that null again?"

Yes I told you cause it's easy to try first without shields... cause you can e.g. modify (e.g. cutting away) the excess of turns to get right frequency etc.
But then you have to apply shields and re-null everything for a real "field-coil", where shield is mandatory.

Re-null as you already made after shielding and connecting shields to gnd as explained by Ivconic.

Don't worry you'll find a good null easier now that you have understand how.

Kind regards,
Max

[Max]

BTW I strongly think now that GSabre could be pushed, with some tricks, at more with DD22, like bandido... and even in the ground.

Don't know why but something say me that I haven't saw anything but just a part of its real potential.

It's very stable ! Or not ?

It's a rock... like bandidoII with right components... but here design supplied to old fashioned and noisy op. amps... and if you put some newer you'll gain more and more stability.

It's really good designed even if it uses old fets !

I'm thinking of pushing 10V on the positive rail to see what happens.

Kind regards,
Max

[tiktak]

Hi,

Hi,
Max.
Its not expencive around 1,2 euro.
I will try!
But still dont understand how to conect when nulling with shields!
I have to conect Tx to pcb and Rx to multimeter trough 1k resistor and 15n cap.But waht about the shield?Should they be conected and if so where?
Thanks

[Max]

Hi,
Max.
Its not expencive around 1,2 euro.
I will try!
But still dont understand how to conect when nulling with shields!
I have to conect Tx to pcb and Rx to multimeter trough 1k resistor and 15n cap.But waht about the shield?Should they be conected and if so where?
Thanks

Hi,
to TX side GND on PCB. You have to connect both shields using two distinct wires at gnd point at tx lead in searchcoil. Then that unique wire goes to the TX PCB PAD.
After nulling you have to reconnect rx leads as before. If you swap rx-tx (during shielding phase) relative orientation you'll try to swap rx leads to gain correct phase as you've previously done before.

If you'll use foil use a roll say 2cm wide and don't overlap too much, but cover well and uniform.

Kind regards,
Max

[tiktak]

Hi,

Hi,
Max.
What did you use to fix the coils still?
I am using epoxy resin,but not setisfy!Hard to work with~~~!!!

[Max]

Hi,
Max.
What did you use to fix the coils still?
I am using epoxy resin,but not setisfy!Hard to work with~~~!!!

Hi,
I always use epoxy. It's the only thing to use if you want make a real search coil. Almost all commercial vlf coils have it inside to seal and fix windings.

You can keep your nulling position easy and then obtaining a very rigid structure.

There are lot of instruction about it in some older projects documentation.
Already discussed many times here.

Best regards,
Max

[Max]

Hi all,
this is my idea for a simple audio mod...

Rf sets the gain, with Rf=120ohm output power would be about 2 W

One could use an e.g. 1K pot to mod the output volume.
c8 = 1.5nF.

Quiescent current +4mA (no sound).

may work good ? who knows ?

Have to test.

Kind regards,
Max

[tiktak]

Hi

Hi,
Max:

You can keep your nulling position easy

HOW?

[Max]

Hi,
Max:

You can keep your nulling position easy

HOW?

Hi tiktak,
when you mix the components you have a fluid state of resin that have an about fixed duration (depends on products, but usually several minutes).
During this time you can fill the wounds with the fluid, that way you haven't to use any strong force so that you'll lose the alignment of them.

The trick is mixing a few epoxy and start covering from the outer shape, leaving the central area as last thing.

Then before seal the central part of overlap of the two windings you can recheck for right null (if there was some movement) and renull also.
Then seal a point at a time, till you seal it all keeping the nulling !

Not so difficault if you have time, patience and goodwill.

Best regards,
Max

[Max]

Hi all,
this is my idea for a simple audio mod...

Rf sets the gain, with Rf=120ohm output power would be about 2 W

One could use an e.g. 1K pot to mod the output volume.
c8 = 1.5nF.

Quiescent current +4mA (no sound).

may work good ? who knows ?

Have to test.

Kind regards,
Max

Tested it... and seems not good. Best using it after the c517.
Audio is strong but I'm not satisfied of whole working.

[tiktak]

Hi

Hi,
Max.
I will use this method.
But the interesting think is that when I null now and conect again I dont have good performance,but when I separate the windings the md give good sound??
Why?
The null should be the best point,and this is almost 1 cm away?!?!?
I havent time today to buy 3240,but tomorrow will for shore!
Thanks

[tiktak]

Hi

Can the audio from magnum be used here?