King Cobra PCB

[kt315]

waltr is sure accurate. thank you. use 3 turn pot for GB. '3T pot'.

[waltr]

Yes, the two holes should be joined on the PCB. The reason there are four holes is to use two different size pots. This is also known as a 'dual footprint' allowing a wider selection of parts.

Linear or Logarithmic depends on the pot's function. Most likely they are linear.

[RelicHunter1388]

Happy New Year to all!!!

I am currently designing the Control Box. I want to have Ground Balance and Notch Width potentiometers adjustable by the user on the field.



That is easy to do with small cables soldered on the PCB, however, potentiometers have three connectors (1, 2, 3), but the PCB has four holes for the trim potentiometers (see picture below). Two of the holes seem to be on the same line, therefore, should these be joined?



Also, since the trim potentiometers are 100K, the normal potentiometers, logically, must also be 100K, but, should they be logarithmic or linear?

[RelicHunter1388]

Thank you for the valuable information!!!

Don't worry, will use the proper 7343H capacitors and 1206 resistors.


All components will be here shortly. I had to order a lot of them because old electronics are almost impossible to find these days. You can find newer ones, but these use modern PCBs with tiny SMD parts. Some components are coming from aboard, so it will take some time until I can start the assembly.


In the meantime, will work on developing schematics for a practical detector frame (stick) and Coils. I think I will go with two Coils. One standard and one small for pinpointing. As a way to give back to the community, all that will be free if anyone is interested.


Specifically, I have in mind something like the small coil in the picture.


But using the tiny coil like the guy in the picture does is impractical. I am thinking of using it with a handle and switching 5-pin cables to connect it to the detector that you can leave around (or you can detach the control box and strap it on your belt or vest). Still conceptualising though. The design must be simple and easy to make and use.

[kt315]

[2] 2MM (BLUE) = ???

two-sound-disc-mode

https://www.youtube.com/watch?v=W-nM5xZbViQ

[kt315]

especial made topic - please learn it before soldering. https://www.geotech1.com/forums/show...-on-boards-LOL!
also, all tantalums are soldered AT THE END of job, after all.

[kt315]

if you use same size (in mm) tantalum so with lower voltage (10V, not 16) you can set a cap with more value (in uF).
look on the dimensions, not on the values. you can set ANY value, but there is/exist some maximal value for 'fixed' dimentions.
it is.

Does this mean that the capacitors used can be between 22 and 47uF? Is 47uf better?

yup. 2.2 4.7 10 22 33 47. 47uF is better
pls use just SMD tantalums. type 7343H.

[kt315]

--------------Voltage
C43 Bottom >= 16V
C55 Bottom >= 16V
C56 Bottom >= 16V
C57 Bottom >= 16V
C58 Bottom >= 16V
C59 Bottom >= 10V
C60 Bottom >= 25V
--------------VALUE
R79 Bottom 18-24Ohm
R80 Bottom 18-24Ohm
---------------------
R81 is absent, do not set it

[RelicHunter1388]

Hello, I cannot understand some things about the SMD capacitors. Can anyone clarify?

In the part list:

7343H C43 22-47uF x 20-25V

C55 22-47uF x 20-25V
C56 22-47uF x 20-25V
C5722-47uF x 20-25V
C58 22-47uF x 20-25V
C59 22-100uF x10-25V
C60 22-47uF x 25V

Does this mean that the capacitors used can be between 22 and 47uF? Is 47uf better?

Capacitor C59 is different (22-100uf) but it is grouped with the others in the same group. Should I go with 100uf?

[RelicHunter1388]

That information is a treasure! Thank you so much for sharing it kt315!!!


Now every piece of the puzzle falls into place. The MODE Switch is of ON-ON-(ON) type. This way, when the switch is in the middle position, the Discrimination circuit is closed and connected to the Fixed Position.


More precisely, the MODE SWITCH positions are:

ON [Left] (DISCRIMINATION) = 1MM + 1MR , 2MR + 2MM (5 + 6out , 2in + 3)
ON [Middle] (ALL METAL) = 1MM + 1ML , 2MR + 2MM (5 + 4out , 2in + 3out)
(ON) [Right] (SET ALL METALL) = 1MM + 1ML , 2MM + NONE (5 + 4out , 2in + 1out)


With the cables and poles

[4] 1ML (YELLOW) = Momentary Position Set
[5] 1MM (GREY) = Fixed Position All Metal
[6] 1MR (GREEN) = Fixed Position Discrimination
[2] 2MM (BLUE) = ???
[3] 2MR (WHITE/RED) = Discrimination
[1] NONE


Also, if every toggle switch of this type follows the same principles as the T80-T Series I referenced, then the keyway should go to the right for the momentary (ON) position to be on the right.

I also made a picture by adopting a picture from a previous post:



Now, I only have to find one of these super-rare ON-ON-(ON) switches...

[kt315]

'mode' switch on the panel. colors of wires marked on the circuit.

[kt315]

second section of the switch look on R53 R55

[kt315]

i bought KING COBRA at ebay, for back-re-design, so this text was in owner-seller listing.

-----

I have for auction my Gold Mountain King Cobra metal detector.
This has been a backup detector and has seen little use and is in excellent Fully working used condition.
This is a used metal detector and there are slight use age marks but as you can see from the
pictures its in way above average condition for its age. I am only the second owner of this from new.
I have taken photos of all angles so you can see the condition of all parts.
I bought it primarily as a backup machine, it has been very well cared for and all controls function
as they should. Please note the mode toggle switch is a 3 way toggle, left for discrim, centre for all metal
and right spring loaded reset. The notch toggle is just 2 way accept/reject.
No headphones come with the detector. The headphone socket fits standard 1/4 inch
headphone plugs. Battery is NiMh and gives over 20hrs continuous use. Charger provided.
The battery is accessed via a panel at the front with two button clips.
A VLF slow motion discrimination detector using an 8" concentric coil, the detector operates at 15khz. Weight 3lbs
Auto ground balance, All metal and pinpoint non motion with adjustable notch discrimination if required.
This detector when first released was top of the range and is quite sought after due to its simplicity and
excellent iron discrimination.
Over the years i have owned most makes and type of detector and liken this to the laser/tesoro machines
in both ease of use and excellent detection of small silver coins and gold, roman coins etc.
I have enclosed a copy of the original instructions.
I will post by parcel courier to any uk address, sorry i am not shipping overseas.

******I will pay for postage******

******UK ONLY POST****** NO RETURNS

Any questions about the detector please contact me by ebay message.

Payment by paypal please.

This auction is fixed price buy it now, no offers please.

[RelicHunter1388]

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.

Is the MODE switch an ON-ON-MOM type?

I have the PCB for ten years and now that I got the time I decided to finally build it. So far I found ON-OFF-MOM switches (MTS-213 DPDT 6-Pin and MTS-113 SPDT 3-Pin) that are apparently very rare, and some even more rare, and also very expensive, used ON-ON-MOM switches from the States (that will cost as much as a used metal detector to ship here).

But, if in the Parts List the NOTCH is a "3 Position" and that translates to ON-OFF-ON, then the MODE, which is a "3 Position with momentary" should be a ON-OFF-MOM, right?

However, in a previous post it is stated that a CMOS opamp for IC8 must be used in order to be able to use the ON-OFF-MOM SPDT switch. Is that integrated into the King Cobra PCB? Or it has to do with the switch type? Namely, ON-OFF-MOM DPDT is what should be used for the King Cobra, but a ON-OFF-MOM SPDT wan be used if a CMOS opamp for IC8 is also used?

(The MTS-213 DPDT 6-Pin is what seemingly what it is used in most builds, but I cannot make the markings from the pictures, therefore I cannot confirm.)

[kt315]

I WOULD LIKE TO ASK IF THE PCB FROM KING COBRA ARE IN STOCK ?? IF YES COST FOR 2 PIECES ??

whole batch was been sold. i am at end of refreshing of the layout now.
late i will order new pack.
pleasure