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King Cobra PCB
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Originally posted by growdude View PostCan you provide parts list and pot pin out?speaker connection point etc?
that you have to see at photos.
batts, power supply connection. -8V checking in Test Point. - 7,54V is good, you can use also Schottky diode vice 1N4148 and get slightly more voltage [in modulus], but it is not so principeilly.
http://depositfiles.com/files/vouilfpv3
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Originally posted by kt315 View Postcertainly. it's easy for me because the schematic is primitive.
that you have to see at photos.
batts, power supply connection. -8V checking in Test Point. - 7,54V is good, you can use also Schottky diode vice 1N4148 and get slightly more voltage [in modulus], but it is not so principeilly.
http://depositfiles.com/files/vouilfpv3
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I know for sure that BF245 geometry is symmetrical, meaning that it is exactly the same from drain or source, which makes it a good choice for our purposes. A, B, or C would not make much difference because you are using it in switching and not linear regime, and series resistances take care of channel resistance differences ... which are not that critical at all.
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Originally posted by Davor View PostI know for sure that BF245 geometry is symmetrical, meaning that it is exactly the same from drain or source, which makes it a good choice for our purposes. A, B, or C would not make much difference because you are using it in switching and not linear regime, and series resistances take care of channel resistance differences ... which are not that critical at all.
J107 works fine for me too. BF245 is acting the same. Simply because fet there is used as simple switch. Further those can be replaced with 4066 with additional pullups.
It would be good analyze to compare eventual differences between use of fets and use of 4066. Speed, delay,hums etc..etc..
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Originally posted by growdude View PostHi Kt315 can you send me paypal info so i can order one please i also have many pics of mint original king cobra board bot sides if you would like case pics too
my e-mail address [email protected]
I also will appreciate all info on GMT 1650.
THANKING IN ADVANCEAttached Files
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Originally posted by ivconic View PostCorrect!
J107 works fine for me too. BF245 is acting the same. Simply because fet there is used as simple switch. Further those can be replaced with 4066 with additional pullups.
It would be good analyze to compare eventual differences between use of fets and use of 4066. Speed, delay,hums etc..etc..
4066 is slower.
Best of all is 4053.
I've been experimenting with all and that's my opinion.
No offense to anyone.
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15 kHz freq is more sensitive to golden nuggets, you know it before
thanks lots, my friends! and I will tell you about our project cutting from Andy Sabisch, artilcle in Threasure magazine.
Gold Mountain King Cobra
By Andy Sabisch
From page 15 of the December, 1989 issue of Lost Treasure
Copyright © 1989 Lost Treasure, Inc. all rights reserved
The Gold Mountain name has been associated with treasure hunting for several years now; however, the company has recently been reorganized under the new leadership of Diana Brackenridge. The King Cobra is the top of the Gold Mountain line which presently includes two other models. When I was contacted and asked if I was interested in doing a filed test of the King Cobra, I readily accepted.
FEATURES
The King Cobra is an automatic ground canceling, silent search, slow motion discriminator with a non-motion, all-metal pinpoint mode. It also features an adjustable notch discriminate window with both accept and reject settings, as well as dual-tone, audio target identification.
The King Cobra is mounted on modified S-shaped rod, and at 3 1/8 pounds is not only extremely well balanced, but also about the lightest full-feature detector available today. The armrest breaks down into three pieces which makes traveling with the King Cobra a real pleasure. The armrest also features a built-in stand which not only keeps the detector upright when digging, but also keeps the control housing away from damp grass or dirt as well.
The lower rod that connects to the search coil is as sturdy, 17-inch plastic isolator shaft which helps eliminate the interference normally experienced with a metal shaft. The search coil is lightweight eight-inch, ultra thin design that is ideally suited for shallow water hunting.
The control housing is easily removed from the rod for either hip-mounting or shallow water hunting by pressing the two sets of spring clips under the housing, and the bracket then doubles as a belt loop. The searhcoil comes with six feet of cable which eliminates the need for an extension cable when removing the control box from the rod.
The controls on the King Cobra are three knobs: Sensitivity Level, Discriminate Level, and Notch Window Adjustment. There are two toggle switches, Mode Select and Notch Setting. There are PRESET markings on both the Discriminator and Notch Adjustment knobs which simplify the initial set up of the detector.
The controls are well laid out an easily accessible. The headphone jack is located on the lower right
corner of the control box, and is situated so as not to interfere with the controls during operation.
The King Cobra is powered by eight-AA penlight batteries which are accessed by removing the battery door on the rear of the control housing. The expected battery life is around 20 hours, slightly longer if headphones are used. Ni-cad rechargeable batteries can be used with no effect on the performance of the detector.
INITIAL IMPRESSIONS
After assembling the King Cobra and reading over the instruction manual, I proceeded to perform an air test in order to determine the response of the detector to various targets. The King Cobra is turned on by rotating the Sensitivity knob clockwise.
The automatic battery test is performed each time the detector is
turned on, and the battery strength is indicated by the length of the tone heard. When the tone lasts for one second or less, the batteries need to be replaced. I was pleasantly surprised at the sensitivity of the King Cobra especially to small jewelry items, even white gold and platinum.
The dual-tone audio target indentifaction provides a distinct tone for each target depending on where the target is detected in relation to the setting of the Notch Adjustment knob. Targets that fall above the setting on the Discriminate Adjustment knob and below the setting on the Notch Adjustment knob produce a low pitch tone, while targets that fall above the setting on the Notch Adjustment knob produces a high-pitch tone.
The nice features with the audio identification is that it works even when the Notch Discriminate circuit is turned off. This allows one to operate the King Cobra with a low amount of discrimination, and use the audio discrimination to identify targets before digging.
I used several targets including a nickel, pull tabs, screw caps, rings, a zinc penny and a copper penny to test the notch discrimination feature of the King Cobra. Ive found that
notch discrimination is probably one of the least understood yet most useful features on metal detectors today.
When using notch discrimination in the Notch Reject setting, you can reject most of the pulltabs and screw caps in an area while still detecting nickels and most gold rings. The Notch Accept setting allows you to set the detector to respond to a specific range of targets which is extremely useful when searching for tokens in a competition hunt or for shallow water hunting as will be explained later.
I found that the preset maits on the Discrimination and Notch Adjustment knobs were quite accurate, however, I was able to fine tune the settings slightly by checking the response of each of the test items and adjusting the Notch Adjustment knob as needed. When searching the Notch reject mode, it is important to note that if you are rejecting both pulltabs and screw caps (Preset Mark on the Notch Adjustment knob), that you will also be rejecting zinc and Indian head pennies.
If you are searching in an older area, it is best to adjust the notch level so the detector will respond to some screw caps as well as the older pennies. By using a zinc penny(l982
or later) to find the setting at which the detector begins to respond, you will know where to set the Notch Adjustment knob if the area you are searching has the potential for producing older pennies.
Never use more discrimination that what is needed to reject most of the trash items in the search area. If you dig no trash items at all, you are probably missing some better find.
After completing my familiarization with the controls, I took the
King Cobra outside to see how it responded to various objects in my
test garden. With the detector controls at Preset and in the Notch Reject mode, it gave clear, repeatable signals on all of the good targets which included a dime at five inches, a quarter at seven inches, two gold rings at four and five inches, and a nickel at five inches.
The King Cobra did not give any response to a nail at four inches, a screw cap at four inches and pull tabs at three and five inches while in the discriminate mode, however, the detector did respond to the targets when in the all-metal mode.
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