Garret ACE series DIY coil help

[guiseppi]

Hello. I was hoping to make some bigger and smaller coils for the 250, because cost is prohibitive atm.
I found this diagram somewhere in the universe which seems close:



But doesn't match the continuity/measurements I made, as follows.
On the Search Coil socket:

pin 1-4 5.135 mH 6.1ohm (I guess this is TX?)
pin 2-3 3.07 mH 35ohm (And this would be the RX and bucking winding?)
pin 5 - Not Connected

On the control box, pins 1 and 5 are both GND.
Plus it seems the shielding may be attached to a positive voltage and not GND?

I have a couple questions.
Is there any more circuitry within the search coil itself? (Caps whatnot)
Can anyone help with how to go about winding a DD coil instead of the
default one and would a standard DD nulled in a typical way even work in this circuit?

That's all for the mo

[kt315]

take attention that the coil schematic you attached here is NOT Garrett original. this only was a try to repair a broken coil via non-standart way.

good luck anyway

[ZTDMP]

http://www.md4u.ru/forum/viewtopic.php?f=9&t=3542

[guiseppi]

Thanks for the link.
A piece of the text Babelfish translated: (Related to DD prototype coil, not the Garrett original)

"[Tkh] we twist connecting to the instrument controlling frequency, we reach to 7.1 and it is good. (Wire 0.5-0.55) [Gdeto] 70[vit].
[Rkh] does not hurry about under the capacity inside the instrument, separate outlet hurries about from 50 to 60 turns + of 2-3 turns.
Diagram of [opdklyucheniya] to [vishe] in the archive."

What is meant by 'reach to 7.1 and it is good' ?

About polarity of coils.
Are the Tx and Rx coils wound in the same polarity and the smaller one of opposite atop the Rx coil?

Is the same resistor network (parallel 100ohm pot, 220 and 300ohm) used in the prototype DD coil between the coils? I see the pot in the pictures..
And what is the purpose of these resistors?

Cheers.

[kt315]

all tuning of the coil discribed detalized. only in russian.

cheers

[guiseppi]

Using zoho and google to translate to english (link should not expire, allegedly)
http://tinyurl.com/366lnf8

[Funfinder]

guiseppi

Hello. I was hoping to make some bigger and smaller coils for the 250, because cost is prohibitive atm.

You can buy priceworth bigger Detech coils from Bulgaria that should work with the Garrett Ace.

[kt315]

may see here as the coil is making... cool video...
http://www.youtube.com/watch?v=USfVBeSQtpM

audio volume tuning mod
http://www.youtube.com/watch?v=XpBAxqjYDQI

[guiseppi]

I modded a pair of Nokia telephone, hands free earplugs to reduce volume, rather than void the warranty. Ripped out the mic and circuitry and put in a voltage divider on L/R, about IN 22-47k -> TAP EARPIECE -> 47k -> GND and replaced the telephone plug with a stereo jack. Works well without destroying both the phones and eardrums.

The Detech SEF are very expensive?
Unless they manufacture other, cheaper ones.

I recently finished the TGSL circuit, etch resist pen drawn PCB, and found it hard to get a good pair of coils. After 3 sets and no match amongst them to give proper operation, resorted to a multi-tapped coil, which allowed a good pairing to be found without any real detrimental effects. I put in taps every 2 winds around the estimated, two each side. Only the RX or TX coil need be tapped for the DD in the TGSL case. That did work and depth is OK, about 5cm better in air than the ACE 250.

I think I will use this method to make it easier to make search coils in future, including for the ACE 250. The ACE TX coil should be fairly easy to get right, but as the ACE requires a little more complicated RX coil, it seems i will have to resort to a bit of experimentation.

Oh. Does the variable 100ohm resistor in the original coil actually tune the null to some degree, or is it simply to increase the RX resistance to about 35ohm for the receive circuitry?

[kt315]

here in video is a test of NEL coil on ACE-250 vs Terra-70, Garrett 2500gti, Signum, Sorex (last both of AKA company, Russia). NEL coil was set also on Garrett 2500gti. NEL coils are make of a company in Kharkov city, Ukrainia. first test is 38 cm on russian coin, second 43 cm (approx 17").

http://www.youtube.com/watch?v=QZWDQ...yer_embedded#!