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Hello, I have built a Stuart I MD, with those modifications:
- 32KHz
- BC547/BC557
- 1N4007 (instead of BY407A)
- 10/100uF for 6.8/68uF
I have shorted pins 12 and 13 of 4011 and swapped boosted supply transistor.
Successfully tested oscillator and boost supply, I heard clicking and I can adjust them with trimmer and potentiometer.
I have then built the search coil as described and connected it to the board.
Now I have some problems: sensibility seems to be very bad, it can discover a pair of scissors at 30 cm (in air) only if i move it. I cannot hear changes in pitch if I move a coin or a bunch of coins even in contact with search coil...
Can you show me what I have to check in order to discover the problem?
I think the problem may be in the coil (low pulse), in MOSFET or in amplifier. But I cannot figure out how to check it.
Thanks.
- 32KHz
- BC547/BC557
- 1N4007 (instead of BY407A)
- 10/100uF for 6.8/68uF
I have shorted pins 12 and 13 of 4011 and swapped boosted supply transistor.
Successfully tested oscillator and boost supply, I heard clicking and I can adjust them with trimmer and potentiometer.
I have then built the search coil as described and connected it to the board.
Now I have some problems: sensibility seems to be very bad, it can discover a pair of scissors at 30 cm (in air) only if i move it. I cannot hear changes in pitch if I move a coin or a bunch of coins even in contact with search coil...
Can you show me what I have to check in order to discover the problem?
I think the problem may be in the coil (low pulse), in MOSFET or in amplifier. But I cannot figure out how to check it.
Thanks.