GA-72Cd Magnetic locator

[ivconic]

After all, a similar "trick" is used in PI detectors with large coils.
For example Pulse Star II, say coil 1x1m or 1.5x1m or even better 2x2m... to avoid detection of small surface metals;
you lift such a coil off the ground and at the same moment there are no more "disturbances" or detection of those small unwanted objects...

[ionut_mtb]

Ah so, it is not your own device?
I am interested to see what such device can do in reality on "militaria" kind of targets.
Say... metal box 40x40x40 (for example) put in a 2 meter deep hole (no need to cover the hole at this time) and see if the device will make any response to it at all.
In case it makes an response; than it is excellent and than I would be very interested to make/copy something similar.
A guy sent me in the past short video of some Ebinger, achieving exactly that, a nazi helmet was in such hole and easily detected with such device.
I was impressed.
Unfortunatelly I lost link to that video, I can't find it on Youtube. It is because the title was in Czech or Polish with special characters (I think) and now it's impossible for me to reproduce any search term on Youtube.
And maybe the video was removed from the channel in the meantime. I don't remember who sent it to me. I am very sorry that I did not download that video to my computer.
I may have added that video to one of my posts here on the forum in the past, but I can't find it now.
But from what I saw it; I was impressed, and since then such devices are very interesting to me and I want to make or acquire something like that.
Of course... money is always a problem, such a new "Ebinger" is far beyond my means.
If I am not mistaken, if I remember correctly; it was an Ebinger Magnex 120 model.

Managed to make the detector working again (power side). After alcohol cleaning and reflow some corroded pins one via from top to bottom was not making contact anymore.

Now, regarding the audio output (pin 1&7 where piezo is connected) op282 (power supply is ok), if i connect one speaker from pin 1 to gnd or pin 1 to + i have clear and loud sound. (Also if i connect pin 1 to pin 5 and pin6 i have sound) But if i connect speaker at pin 7 to gnd or pin7 to + i have no sound. I assume op282 opamp (one of them) is defective.

When i will make some time, i will test the device for you.

[ivconic]

Attention!
You must not connect a regular speaker to the piezo output!
There's a chance you'll burn the opamp.
Piezo is triggered by a DC signal while speaker is driven by an AC sound signal.
Be carefull!

[Altra]

Is it possible the headphone jack corroded? This might cause the problem since it is switched through the jack.

[ivconic]

Is it possible the headphone jack corroded? This might cause the problem since it is switched through the jack.

Yes that's true. Actually a common "fault" at older devices.

[ionut_mtb]

Is it possible the headphone jack corroded? This might cause the problem since it is switched through the jack.

Headphones have low volume same as piezo. I’ve checked the on/off switch(phones/piezo) from headphone connector and the contact is ok. The only thing I suspect is the output IC, because, again, psu for ic is ok. I need to put the scope on imput of IC to see if it is good.

[ivconic]

You can replace it with TL082 and check.
...072
...062
...

I missed reading (if you mentioned); are the piezo and headphones connected to the same "source"?
It shouldn't, because of the impedance differences.
If they are, then the suspicion on the opamp is justified, if they are not, they are driven from different "sources"; then maybe it's some other problem.
In older devices, it often happens that the resistor increases in value.
Rarely but it happens.
Check all resistances in that circuit.

[bklein]

I’ve bought and repaired several ga52cx’s and CTX/Berger models. I haven’t come across a bad electronic part yet. Always the switch, audio jack, or bad connection. Try flexing the board to see if you get audio. Spray deoxit on the jack connections. Volume control might be bad.