King Cobra PCB

[kt315]

Jurgen, beautiful work, but I see a mistake. you have to turn the resistors R79 R80.


good luck

[Miata]

Anatolij, thank you for the hint. I have replaced the resistors.

I have make first tests, the discrimination mode works with some inteferences, but the all metall mode works not. No metall is detected.
I checked values of all parts and solder pads. Perhaps an OPAmp is fault.

Regards
Jürgen

[Qiaozhi]

Anatolij, thank you for the hint. I have replaced the resistors.

I have make first tests, the discrimination mode works with some inteferences, but the all metall mode works not. No metall is detected.
I checked values of all parts and solder pads. Perhaps an OPAmp is fault.

Regards
Jürgen

When you build a project like the King Cobra, it is always advisable to build and test the design in sections. Not simply solder everything onto the board, switch on, and hope it works. Nine times out of ten (Murphy's Law) you will be unlucky.

You should start with the power supply, and work forward from there.

[Legaucho]

Anatolij, thank you for the hint. I have replaced the resistors.

I have make first tests, the discrimination mode works with some inteferences, but the all metall mode works not. No metall is detected.
I checked values of all parts and solder pads. Perhaps an OPAmp is fault.

Regards
Jürgen

Hello Anatolij,

I have exactly the same problem too; the Discrimination mode works with some inteferences, but the All Metal mode does not work. Do you have some idea.

[eduardo1979]

Anatolij, thank you for the hint. I have replaced the resistors.

I have make first tests, the discrimination mode works with some inteferences, but the all metall mode works not. No metall is detected.
I checked values of all parts and solder pads. Perhaps an OPAmp is fault.

Regards
Jürgen[ATTACH]21475[/ATTACH]

You do not have well connected switch DISC / ALL METAL. The switch must have 3 positions. Medium position is to METALL ALL. Double check the schema and put here a photo of the switch connections. Mine worked the first time.

[ivconic]

BTW could anyone here tells us; does King Cobra suffers from masking problem?
Testing it should be simple;
take piece of mineral and cover some coin with it, than try to detect it in Disc mode.
I tested XP Gold Max Power and it is also liable to "partial" masking problem (watch video bellow).
If you watch my test carefully;
you will notice that audio at GMP changes from high tone to low tone when mineral is between gold coin and search coil.
That's example of masking i am talking about.
In case of TGSL under same conditions: TGSL is not producing tone at all ... or eventually can produce occasional "cracks".
In case of IGSL: IGSL is producing nice low tone mixed with broken high tone.
Deus is producing middle tone when tested like this.
So, is there anybody willing to perform similar test with King Cobra (preferably original one)?
Cheers!

[eduardo1979]

The Kobra do not have a tone for iron. It has two tones, one for the foil and the other for higher conductivity metals. If a coin is placed behind a mineral, the Kobra detects the currency with a low tone, (foil).

[ivconic]

The Kobra do not have a tone for iron. It has two tones, one for the foil and the other for higher conductivity metals. If a coin is placed behind a mineral, the Kobra detects the currency with a low tone, (foil).

So? I see.
Than it is better than TGSL for sure.

[kt315]

The switch must have 3 positions. Medium position is to METALL ALL.

Yes, both switches are 3 positions of. This is seems from the photos I did put.
NOTCH - ACCEPT/OFF/ REJECT
MODE - DISC/ALL METALL/SET ALL METALL.This right position is NOT fixed, not fixedable, is only clickable. Althought you can take and use ordinary 3-P switch, but you have to remember to set the switch in middle position anytime (or fixed left one). SET - I mean you set the S.A.T. circuit to some zero, althought there is nothing new - you have to see this part in TGSL too and may be reading about.

[eduardo1979]

SW

I've drawn the switch connections and added the colors of the wires in accordance with the scheme. I hope I can help with anything.

[Legaucho]

Hello all,

My wires on sitch Mode was in a good order. I unsoldered all wire of the Mode switch and after I put in contact 1ML and 1MM together ( like All Metal mode ). Nothing no sound?

[Miata]

Hello,

with a three position switch, the all metal mode works now. Many thanks. The all metall mode is a little strange without a tone for iron. Next tests outddors.

Regards
Jürgen

[kt315]

Hello all,

My wires on sitch Mode was in a good order. I unsoldered all wire of the Mode switch and after I put in contact 1ML and 1MM together ( like All Metal mode ). Nothing no sound?

1ML with 1MM together is momentary switch position, not effecting all time, the push-and-release position. it resets the SAMPLE-AND-HOLD circuit in some zero state because All Metal is static mode. after you momentary touched 1ML with 1MM, you have to put the switch in middle position on all time, 'neutral position'. then that will be ALL METALL mode.

[kt315]

Hello,

with a three position switch, the all metal mode works now. Many thanks. The all metall mode is a little strange without a tone for iron. Next tests outddors.

Regards
Jürgen

you can try to experiment like you see at diagramm - either 1 or 2, connecting by wire. I yet do not try this way, only expecting that it may be working in ALL METAL mode with the disc.

[kt315]

for better insight.