I am ending.......

[diminute]

My DP is totaly mount, I am begining to probe the MD.

The first dificul is that when a push the autotune, for 3 seconds, the sound disappear, but the sound frecuency is increasing quickly. WHY ????

And the detection is poor. It almost detect nothing.

Have someboby here a description of how this MD circuit work ???? I can´t understand, after the LF357 IC to before VCO... is an integrator ???... how work the autotune in this circuit ????

Thank

diminute

[diminute]

Ohhh

Nobody answer me ???

[chemelec]

Nobody answer me ???

Which Metal Detector is this?

[Max]

My DP is totaly mount, I am begining to probe the MD.

The first dificul is that when a push the autotune, for 3 seconds, the sound disappear, but the sound frecuency is increasing quickly. WHY ????

And the detection is poor. It almost detect nothing.

Have someboby here a description of how this MD circuit work ???? I can´t understand, after the LF357 IC to before VCO... is an integrator ???... how work the autotune in this circuit ????

Thank

diminute

Hi,
I don't remember well DeltaPulse working cause I'm using other stuff in last (several) months and now...but I think that if you have a rapid increase on frequency after auto-tune it's maybe due to some capacitor leaks or to some op. amplifier that draws too much current for bias.
I remember that there is a diagram of how it's intended to work...I mean about timings. The auto-tune , as in XR-71 that's really similar to dp, is done by a feedback path that when you leave the push-button is then interrupted and gives you some minutes stability to the threshold level.
I suggest you to check also the mosfet device...to check to temperatures above 50 °C cause if you have too hot-running device you'll experience thermal drifts. Solutions are :
- changing device with some that have less RDsOn...e.g. BUZ11
- mounting it on some cooling structure...aluminium cooler or anything else
- check dumping resistor...cause if it's too big value you could have too breakdown dissipation on the device...and it warms up easy
- reducing the peak current on it...reducing the tx pulse width or modifing the coil...or also adding a limiting resistor

Best regards,
Max

[diminute]

Thank

I will try to probe that you were said.

Thank,

diminute