MGSL

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Inspired by old goldseeker 15000 schematic.

The original tx oscillators I can't figure out how the multi feedback low pass filter after the cd4024 was supposed to work, I think the component values might have had errors. I decided that the convoluted tx drive was unnecessary. So I changed to a more conventional approach as in the Fisher 1280x aquanaut. Everything else is pretty much the same.

Notice only all metal channel as it's supposed to be gold detector like the lobo lite.
Non ferrous discrim can be added later if I wish to take it further.
The zip file contains various Sims of which the audio section I thought was interesting with the jfet switch when headphones are plugged in.( Have a look at the original scheme, at least I think so).

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The schematic needs tidying up and the components values inserted, but that's the easy part.
This is meant as design concept.
Later guys.

[6666]

good work

[ivconic]

Cool attempt!
Obviously lot of space for improvements and modernization.
What about coil specs?

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Strangely, on original scheme, pin 11 of 4024 is divide by 4. If the clock is 32khz then that puts the output freq. @8khz, too low for gold prospecting. Yet it is minelab goldseeker! 16khz seems to be better. Maybe lahr made error in pin on 4024. Don't know.
Anyways, on original scheme, 8Khz@ 390nF results in a tx coil of around 1mH. Typical value for tx coils. The RX would follow conventional typical high inductance value. so a standard off the shelf coil can be used, no need for self made. Bumping the frequency up to 20khz would require recomputation of the filter values of the channels (multi feedback low pass topology), at least I think so.
Lahr has unique way of drawing schemes which looks like the plan for a funny farm. A redraw would make it look so much better. There is no magic here.

[mmh]

Hi
Simple post, it might be helpful

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Indeed, I see you have been paying attention. Thanks. Those who have eyes to see, let them see.