Full m/lab SD2000 schematics

[Andrei]

Compare N12 and N14 to the output of the second 5534(n50) and post the result, I will tell you if it looks ok.
Cheers Mick

[Mechanic]

Looks good to me!

[ionut_mtb]

hello, i've noticed all sd/gp detectors have ferrite rings over the coil leads and power leads. Can someone tell me which type of noise we have/frequency range so i can choose the right ferrite? color code can be different from manufacturer to manufacturer.

[Andrei]

Looks good to me!

Oscillograms on tuning resistors, in the presence of metal on the coil

[Mechanic]

Ionut_mtb, the ferrite ring is for radiated emissions for emc compliance purposes. I have seen orange ones, grey ones and big long black ones!

Andrei, the trimmers, get a black ferrite magnet from a small speaker, no metal, just the ring magnet. Short out 2 of the channels with the jumper testpoints at the lt1057. Raise and lower the magnet to the coil(center but not all the way to the coil, 2 to 3 inches above coil is fine) and listen to the audio. Adjust the trimmer to not pick up the magnet. Do the same for the other 2 channels. To do the GB channel you need to adjust the gb to be on full.

Cheers Mick

[ionut_mtb]

Ionut_mtb, the ferrite ring is for radiated emissions for emc compliance purposes. I have seen orange ones, grey ones and big long black ones!

Cheers Mick

Thanks, i understand, but why it has ferrite ring on the RX side also?

[Andrei]

Andrei, the trimmers, get a black ferrite magnet from a small speaker, no metal, just the ring magnet. Short out 2 of the channels with the jumper testpoints at the lt1057. Raise and lower the magnet to the coil(center but not all the way to the coil, 2 to 3 inches above coil is fine) and listen to the audio. Adjust the trimmer to not pick up the magnet. Do the same for the other 2 channels. To do the GB channel you need to adjust the gb to be on full.
Cheers Mick

Thanks, but I haven't made the second Audi Board yet

[Mechanic]

Thanks, i understand, but why it has ferrite ring on the RX side also?

Don't know. Minelab run all the wires through the same ferrite ring. I guess it is standard practice to run all of the wires in a cable through whatever ferrite is selected.

[ZED]

Hello everyone !

Mechanic is correct,its all about emissions,both transmitting and receiving,the receive also has fast transient pulses on it as well.It is possible to run these P.I. detectors with no ferrites
and they run just fine,but for compliance ferrites are used as part of a solution.

[ZED]

Some Pointers

I would also like to point out that the SD2000 CCT has safety shutdown CCT's built into it,these will shutdown the TX CCT and shutdown the front end receive CCT.
The LM393 monitors the coil current through the bank of 1 ohm resistors (current sense resistors) and if the wave form is not there then it sends a signal through the
CD40106 which in turn sends a signal to the 4053 chip which then sends a signal to the receive CCT and TX CCT which then locks that down as well.

The TLC271 monitors a voltage directly correlated to the 180 volts sitting on the 200v electro,it maintains this voltage by servoing the voltage on the gate of the IRF710,this fet can get hot as it performs its function so a heat sink is a requirement,the fet getting hot is perfectly normal in this application.You will note that the whole CCT,fet,electro and resistors are in the feed back loop of the TLC271,and so the result of this is servoing the flyback voltage at around 180 volts,this stops the TX fet from avalanching as the flyback voltage begins to climb.An avalanching TX fet with 3 amps at switch off can make the TX fets very hot.

Cheers.....

[waltr]

Ionut_mtb, the ferrite ring is for radiated emissions for emc compliance purposes. I have seen orange ones, grey ones and big long black ones!
Cheers Mick

Thanks, i understand, but why it has ferrite ring on the RX side also?

Hello everyone !

Mechanic is correct,its all about emissions,both transmitting and receiving,the receive also has fast transient pulses on it as well.It is possible to run these P.I. detectors with no ferrites
and they run just fine,but for compliance ferrites are used as part of a solution.

Correct, Ferrites are Only for CE/FCC compliance. They do NOTHING for coil noise pickup or detector performance.
What they do is reduce RF Emission from inside the detector which could cause interference to other electronic devices.

[ZED]

Hello Anis

Please see attached image,it shows the coil current waveform on a SD2000 using a 100 milli ohm 5W power resistor (the white blocky ones), 1 ohm is too high and will affect the current going into the coil to much.The scope is set to 100 mv and each gradient on the screen equals 1 amp of coil current,this is what you need to see on your scope,mind you my supply voltage is over 8 volts so a 2000 on 6 volts will show less coil current,but over all the waveform should look roughly the same.
You will also note that the coil current doesnt flat top,this is normally the case with the SD2000.

[ionut_mtb]

Hello everyone !

Mechanic is correct,its all about emissions,both transmitting and receiving,the receive also has fast transient pulses on it as well.It is possible to run these P.I. detectors with no ferrites
and they run just fine,but for compliance ferrites are used as part of a solution.

thanks!

[Suhoj57]

This is the signal from the coil ... this is the signal on the fet gate.
When I connect a coil to rx or drain of vn fet the transistor heats up
and does not conduct and interrupts the signal on the gate vn ....
What could be the cause? TX - ... VN Fet .. PN Fet

[ZED]

Hello Suhoj57

Hmm those signals dont look right,i need to ask a silly question,is your scope probe set to x1 or x10

When i work on a 2000 with TX problems i remove the receive wire completely and address receive problems once the TX CCT is running correctly.A number of CCTS wont work properly until the TX CCT runs right so this is where you need to look first.
I have three pictures for you,one shows the flyback signal that you should be aiming for and the other shows the signal on pin 2 of the 393 chip,that signal is 100mv pp,pin 3 of the 393 needs to have about 52 mv on it or 0.52 volts.

The signal on the gate of the TX fets should be about 11 volts pp

Also try leaving the coil disconnected and see what signal you get on the hot wire going to the coil plug(wire with the flyback signal)it should look like the waveform in the third picture.