IDX-PRO+VDI

[Koala]

Not sure where your going with this - I really dont !!! ??

I got lost several post ago
Seems we have a lot of new builders all starting at the same time. Good choice great project.

Best thing anyone can do that is build from the a silverdog PCB with no modification. Second best is etch the original board with no mods that is known to be 100%

To start with only switch on for a few seconds while checking if anything is getting hot/warm. Everything on a good build stays cold. If something is wrong and blows without this check it can be a right PITA to find later.

Check the voltages

It is also worth measuring the current if you are using a good coil. I posted the current awhile back in this thread with and without sound from a target. Don't worry if it's a bit different but should be in the same ball park

If you have a scope connect the TX and measure the frequency (anywhere near 6.5khz it does not have to be exact) Without this you will get nowhere

If you don't have a scope consider buying a coil. If it does not work you will have no way of knowing if it's the coil or board fault

If you are planning to do any mods don't do them until after you detector is up and running.

Taking little steps is the key

To get consistent results when testing you need the PCB mounted in a shielded/metal case and the coil connector outer shield grounded. Connecting wires short and twisted together. Also worth grounding the POTs. If you use the outer edge of the PCB as ground as most people do then you need to insulate the headphone socket

The detector work perfectly fine outside of the box but when doing air tests you get inconsistent results if you move the cables also it can become unstable.

My detector even though its in a metal box still does not like my soldering iron on and some florescent lights.

My detector is unstable with no coil connected others are stable without the coil connected so just unplugging the cable to test is not enough.

[jlsilicon]

Not sure where your going with this - I really dont !!! ??

As I said, I am trying to debug my circuitry (and so understand it) from the RX Opamps and up...

[golfnut]

Not sure where your going with this - I really dont !!! ??

[jlsilicon]

Hi jlsilicon

Not sure if I'm understanding you correctly, but are you saying that you can move the receive coil a foot away from the transmit coil and still get a signal? Because that's exactly what I'd expect to happen. The oscillating magnetic field from the Tx coil spreads out thru space and induces a voltage in the Rx coil. That's how IB detectors work. This will happen with or without a Faraday shield on either or both (assuming the shield(s) have a gap so they don't act as a shorted turn).

On the other hand, if I've misunderstood you then forget I said anything.

Gwil

Well, the Faraday Shields on the Coils removed the TX to RX Reception down to a few inches now - and removed the background signals (60hz, 1khz,100khz).

With NOT both faraday shields, the range of reception was in feet.
I could even pick up the 60hz signal clearly from the wall outlet at about 3 feet (or more) - even with the light off.

With just the RX Faraday shield, the range was about 1 foot - probably the circuitry picking up the TX osc sig.

If I disconnected the TX Coil, then the major oscillation disappeared (other than 60hz, 1kz, and 100khz lesser background signals) - so it was Reception and not internal osc.

[Gwil]

Hi jlsilicon

Not sure if I'm understanding you correctly, but are you saying that you can move the receive coil a foot away from the transmit coil and still get a signal? Because that's exactly what I'd expect to happen. The oscillating magnetic field from the Tx coil spreads out thru space and induces a voltage in the Rx coil. That's how IB detectors work. This will happen with or without a Faraday shield on either or both (assuming the shield(s) have a gap so they don't act as a shorted turn).

On the other hand, if I've misunderstood you then forget I said anything.

Gwil

[golfnut]

did you add the cap on the coil?

this sounds like self resonance of the coil

[golfnut]

I would suggest put the cells in the right way and you should be good

[jlsilicon]

Simple question :
I am using the Transmitter circuit and the Receiver Opamp with the 2 Coils.

But, I pickup the Oscillation at large distances like 1 foot or more.
Why is this - is this the radio Transmission instead of the magnetism ?

Ok got it, I did not have a Faraday Shield - so I was picking up the Radio Transmission from the TX Coil.

[jlsilicon]

Simple question :
I am using the Transmitter circuit and the Receiver Opamp with the 2 Coils.

But, I pickup the Oscillation at large distances like 1 foot or more.
Why is this - is this the radio Transmission instead of the magnetism ?

[ampirate]

Actually, I am trying the Transmitter circuit, the 2 Transistors and Coil.
But I am reading like 100KHz on my oscilliscope.
Does this sound right ?
I have checked over the parts again and again ...

[Koala]

Kycoin

Do you have a multi meter if so easy to check http://www.allaboutcircuits.com/vol_3/chpt_3/2.html

With the batteries being plugged in this will be your first port of call

[kycoin]

Hello golfnut I did find the batteries in the wrong way (grandson wanted to help) so I will try and find if anything is getting hot.

Hello Koala I will get a new set of batteries and try..
I have to go away for 7 days so will ckeck on my return. I only have volt meter to check current, checked the power to headphone plug 0.5volts.

best regards

[Koala]

I have a IDX pro with the Mr bill mods, it has worked without problems for two years but today I turned it on and nothing dead !!
Could anybody advise me where to look for problems.
Voltmeter says 11.2 volts at the board when turned off and 2.3volts when turned on.

thanks in advance

Check if anything is getting hot.

Take it you have checked the batteries. I have had a faulty battery from new before now measures okay until under load.

[golfnut]

Did the batteries ever get fitted the wrong way,, if so there may be a protection diode that got smoked and is a short.

other than that sometimes electrolytic caps go short.


Try it with the coil disconnected, if you still get the severe volt drop its not the Transmitter or the coil.

[kycoin]

I have a IDX pro with the Mr bill mods, it has worked without problems for two years but today I turned it on and nothing dead !!
Could anybody advise me where to look for problems.
Voltmeter says 11.2 volts at the board when turned off and 2.3volts when turned on.

thanks in advance