DIY coil for Fisher Gold Bug DP

[bernte_one]

Hello,

i have a clone or a similar product from this detector


the china machine i got works perfectly the same way with the original coils

but the coils delivered with the clone seems to be not tuned 100 percent well

i think this are out sorted coils

coil datas from my clone coil (but at first from the small white nugget coil)
pin 1+2 8,12mH 33R
pin 3+4 0,872mH 2,3R (-minus resistance of my measure cable 0,2R 2,1R)
pin 5 nc

can anyone compare this with his original fisher gold bug dp coils please

regards

[Silver Dollar]

Here's the schematic. If you know the frequency you might be able to figure the inductance's...

Oops this is the older model. Yours might be different. The manual for the new one says 19Khz.
You would have to put a scope on the TX and see the frequency and amplitude of the transmitter
to see if it needs tuning and look for the RX tuning cap...

A new coil on Ebay is $100;

http://www.ebay.com/itm/FISHER-GOLD-...-/151186321628

[bernte_one]

thanks Silver Dollar

but i´m talking over a newer machine
with lcd display... you should look this pictures

[kt315]

there is not fisher you write about. it is first texas company machine. teknetiks, fisher, (new design) bounty hunter - they are same. fisher is a trade mark. ((TM))
gold bug... this is a name taken for some advertizing. the name is old, taken from oldie model, because famous or I do not know... no more Fisher (c), is fisher (tm).

[bernte_one]

hello

here are the coil datas
for big coil from clone
1+2 43R7 8,61mH
3+4 2R9 0,846mH

orignal g2 coil has only the difference that the resistance of rx coil pin 1+2 has 54R

i heared the clone coil could have some problems with real ground, not time to test this at this moment

regards

[Germanicus]

My Coil Data

My Goldfinder GG2 Coil ist quite bad. I can only archive 25cm with a 2 Euro Coin in Airtest @Gain 100 In Disc-Mode. Over Ground it is very anxious, so only Little Gain can be selected.
Pin 1-2: r=41,9 Ohm, L=9mH
pin 2-3: R=1,8 Ohm, L=0,85mH

Why ist this Coil so weak? Badly shielded?

[Germanicus]

I made some more measurements on my Goldfinder-coil.
The coil-resistance is in both directions the same (1->2 = 2->1), seems like no electronics are between.
The Capacity between coil (12) and coil (34) is 0,34nF
The Capacity between coil (12) and pin 5 is 0,26nF
The Capacity between coil (34) and Pin 5 is 0,41nF.
The Capacity between Connector-Metal-Case and all the Pin is negligible

I guess that the shields of the coil are connected to pin 5?
The connector-metal-case is not shild?
The coils-endings itself are not connected to the shield.
What do the pros think?

Can someone make the same measurements on an original Fisher oder Teknetics coil?

[bernte_one]

hello germanicus

today i make the next step
i have posted first result of tx data on dtektorforum too but you have seen already i think
so for a dd shaped round coul 27cm for mikron style shell
tx 40 turns 0,4-0,5mm enamled copper wire
rx 128 turns 0,18 - 0,25mm (0,25mm gives around 30R a bit too low for original specs so better 0,18-0,2mm)

shield made of graphit powder with clear laquer resistance with one layer of shield paint und 40K

good luck

[bernte_one]

please
can anyone check the pin connection inside the connector plug from the real original coil
where goes the shield?

[Germanicus]

I have got an original Teknetiks G2 Coil (a quite early sample).
Messurements made with Voltcraft VC940 (quite good device).
R Pin1->2 (and also reverse) = 53,2 Ohm
R Pin3->4 (""") = 2,0 Ohm
Cap Coil12->Coil34 = 0,27nF
Cap Coil12 .> Pin5 = 0,283nF
Cap Coil34-> Pin 5 = 0,362nF
Cap Connector Case -> any other Pin = 0,0xxnF (negligbible)
Coil 1-2 determined with series resonant circuit with C = 9,03 nF; f (res) = 17,5 kHz -> 9,16 mH
Coil 3-4 determined with series resonant circuit with C = 76,025 nF; f (res) = 19,4 kHz -> 0,885 mH

[bernte_one]

Attention the following pictures may be stop your heart beat
made them some minutes ago












thanks for your measurements

[bernte_one]

and here the rest

[pnp007]

i also have fisher gold bug pro china. 5 inch coil ok, but 11 inch coil cant ground balance and very noisy when touch grass

[Silver Dollar]

Noisy when touching grass usually means it's not shielded...

I have a cheapo that I'm trying to open the coil. For the last month
I've been running an Xacto around it to separate the half's. Maybe
I'll be in by New Years!

I'd love to see the schematic to that Goldbug above. It looks like
and updated one using a PIC. I've just started experimenting with
those, it's a blast writing code to make it do what you want!

[pnp007]

hi bernte_one any update?