TEKNETICS TEK S/T

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That was about 30 years ago, so a little foggy. As I remember it, you would blindly press the spring loaded switch down until it quit chattering and up until it was unstable. What I do not recall, is if it took repeated toggles or if you could just hold the switch? I noticed in the Findmall thread Sven who is a member here owned one. Maybe he could give a clearer description?

Regardless of how the up/down toggle switch worked, I want to replace its action with a manual sensitivity pot. That would require a scheme change in the circuit.

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I could probably go with a 24V battery to power a typical Tx with the standard phase shift comparators to drive the X and R demods. Or maybe go the Nautilus/Aquasound route to achieve a very high peak to peak. But that would require winding a special coil which I'm not going to do.

[ivconic]

http://www.geotech1.com/cgi-bin/page...le=patents.dat

Precisely this:

https://www.geotech1.com/pages/metde.../US4677384.pdf

[Altra]

Regardless of how the up/down toggle switch worked, I want to replace its action with a manual sensitivity pot. That would require a scheme change in the circuit.

I think you could just replace the up/dn with the sensitivity circuit from the Baron base schematic or Cobra's so called power control

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I think you could just replace the up/dn with the sensitivity circuit from the Baron base schematic or Cobra's so called power control

There is a sens pot on the revised schematic, but I don't see one on the previous scheme. I need to compare the two schemes to see what's going on.
TEK S-T REVISED_-_TEK LTD_0.pdf
The revised scheme has a beach mode. Wouldn't you know.

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Actually, it is just a simple change. As I suspected it would be, but nice to actually see it drawn out in the revised scheme. It would seem that the toggle up/down switch being used to adjust the sensitivity was thrown out in favor of a manually adjusted pot. Interesting. I will have a new schematic drawn soon. A slim down version, only for beach hunting.

[Altra]

The revised sensitivity using a pot looks like a better solution.

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my slim version is taking shape, sens pot included. It will be configured for beach mode only. The power supply, Tx oscillator and phase drive will be a departure from the original though. Nice thing is I can use an off the shelf factory made coil for testing.

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I would like to replace those transistors with ant-parallel diodes but they conduct at slightly smaller voltage compared to the transistors, I'm not sure how this will affect the performance of the circuit though.

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progress

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Tx oscillator, phase and quadrature drive added to scheme. This is where I changed the circuit. So far, so good. I will resolve any errors later on. The structure of the scheme is becoming clearer.

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Earlier in the thread I made a calculation on the internal clock frequency of the LM3578. I don't think it is correct. The Tx freq. is supposed to be 6580Hz.

[Altair]

I am looking for some info regarding the Tek S/T coil, like inductances, ecc;
Is there somebody that can help me ?

[Artyom]

I would like to replace those transistors with ant-parallel diodes but they conduct at slightly smaller voltage compared to the transistors, I'm not sure how this will affect the performance of the circuit though.

Hi. These transistors or diodes limit the overload of the chip. Once upon a time I tried to replace the diodes with transistors in the White's IDX detector and I did not like working with transistors. It's better with diodes. But that's my opinion...

[Altair]

I am looking for some info regarding the Tek S/T coil, like inductances, ecc;
Is there somebody that can help me ?

Ok, I dont have found the coil specs but a commercial coil: Bounty Hunter 10 inch Magnum Search Coil (10COIL is the product code) that could be the right one for TEK S/T detector.