A closer look at the AF108 bi-polar drive circuit

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First up, the power supply for this rig.
Looking at the schematic, I can see several rail voltages, namely V+, VC, VE, -V and 0V. There also appears to be an Si7661(ICL7662) charge pump voltage inverter and an LM2904 dual operational amplifier as part of the overall power supply circuitry. There appears to be a "battery alert" and "replace battery" circuits as part of an elaborate power supply architecture. These added features can certainly be dispensed with in a bare bones rebuild of this detector.

[Carl-NC]

I have one of these, somewhere...

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Holmes here.
it was 'unknown' board of iwkonik. he asked what he got. then we went to resolution it is AF108 board.
ask him to share out high resolution pics at sunlight and you will have a pic for copy in SL.

https://www.youtube.com/watch?v=w_35bXpnZn8

White's AF-108 Mine detector. Pulse Induction,air test after some mods.

Yes Holmes, you remember it was Ivica who first came to forum with unknown pulse machine. Later it was identified as Whites detector model AF108, made in England.
Thanks for posting the link for the video. This detector is very sensitive and rather good detection distance. Very smooth audio VCO and extremely stable threshold with fast response. All the ingredients of a very good machine. My aim is to break it down to bare bones, do some analysis, then perhaps use it as a basis for a new project.

[kt315]

Holmes here.
it was 'unknown' board of iwkonik. he asked what he got. then we went to resolution it is AF108 board.
ask him to share out high resolution pics at sunlight and you will have a pic for copy in SL.

https://www.youtube.com/watch?v=w_35bXpnZn8

White's AF-108 Mine detector. Pulse Induction,air test after some mods.

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Here is a schematic titled AF108 P.C.B. A pulse machine with bi-polar TX drive circuit. Firstly, I would like to redraw just the drive circuit and then secondly, the timing circuitry. Followed by an attempt at modeling the timing train on ltSpice. Then perhaps some modifications to the circuit and finally building and testing the circuit(just the TX drivers and bi-polar circuitry).