My Bandido doesn't work !!! Help me

[gregory59]

Hello,

i have made the double side PCB but my Bandido does't work.

First when i checked the -5V power supply, i had only -2V so i have changed the power supply by this one :

https://www.geotech1.com/thuntings/a...ntid=626&stc=1

So now it's good, i have -5V but the bandido doesn't always work .

Second, i have tried to make myself a coil ( Mike method ) and i had the good frequencyon TX ( 10 khz ) and 10,5 khz to RX when I invert TX and RX.
But i'm not sure that the receive field was cancelled.
So the Bandido didn't work. When i mesured the TX frequency, i had 10,1 khz but the RX frequency falled at the same frequency. => ????

Third : i tried to use a garrett ace 250 coil, i had mesured the TX and RX inductance and i had changed the capacitor to have the good bandido frequency in TX and RX, but the same results : nothing !!!

When i switch on the bandido, i hear a beep for 3 seconds and after nothing else.

So now i don't know what to do !!! Even if the TX and Rx coil are not very good, must i hear something ???

Somebody can help me to check point at point ???

Thank you very munch for your help.
Gregory

[Mike]

Some Suggestions

Hi Gregory,

Before I say anything, let me just say I am not the same Mike as the person who created the Bandido coil building information you refer to - I am a different "Mike". Also, I have not built a Bandido (yet).

When i mesured the TX frequency, i had 10,1 khz but the RX frequency falled at the same frequency. => ????

Do you mean, when you measured the frequency of the RX with the RX coil connected to the MC33178 and the TX coil connected to the oscillator circuit? If so, then the two frequencies should be the same, even though the RX coil gave a different frequency when connected to the TX oscillator.

Even if the TX and Rx coil are not very good, must i hear something ???....When i switch on the bandido, i hear a beep for 3 seconds and after nothing else.

OK - the battery check is working Have you tried switching to all metal mode (and click retune momentarily) and checking that changing the threshold control will change the volume. Then try passing a coin by the coil to see if you get a change in volume. Try this with both coils (Mike and Garrett 250).

Are you completely familiar with how the Bandido should be operated. There is a user manual here: http://www.tesoro.com/BandidoIIMicroMax_Manual_1.htm

But i'm not sure that the receive field was cancelled.???

If you are measuring the frequencies with an oscilloscope, you should be able to measure the receive coil amplitude (at the output of the MC3317 to check it is as small as possible. Check this with both the coils. Nulling the coil is pretty fundamental for correct operation of any VLF TR detector.

The more information you can provide, the better chance someone will be able to help you.

I hope this is useful. Let us know what happens.

Mike