Teknetics Eurotek Pro

[ivconic]

Got Teknetics Eurotek Pro control unit. In bad shape. Somebody already "repaired" it!

[ivconic]

It can power On. Showing normal display.
Membrane keyboard damaged and tried to be repaired with micro switches.
Reacts on commands, enters the menu, seems works alright.
Audio is mum and crakling, distorted.
Q3 blown and chirping.
Some large caps are replaced.
Overall...not good but solvable.
I would like to repair it and bring it to good working condition.
I only need small help on disclosing few component values.
Also i don't know nothing on those machines, working frequency, coil specs etc.
Somehow never was interested enough in those so far.
But i saw few videos on Youtube and i like its behavior.
Seems worth to be fixed and used.
Any useful information?
I already emailed best possible person for this subject, still got no response.
Man is busy, probably, and he will answer me in few weeks as usual.
Until than i am restless.
What transistor is Q3?
Coils specs?

[Skippy]

It looks to have some similarities to the Fisher F2, which I've worked on.
The operating freq is 7.8 kHz. The coils are the same as the Fisher F5 / Teknetics Omega/Delta etc / G2 / Fisher GoldBug Pro , just a TX coil, no internal capacitance. The tuning cap is C7, that pale green one. The one next to it, yellow C4 is part of the pre-amp. This is a regular non-inverting opamp stage, with C4 and a low-value resistor ( under 200 Ohms ) in series going to ground.
The missing electrolytic is probably 47 microfarad , part of the power-on off circuit, or just general decoupling.
I have no idea about Q3, but it is probably an ordinary npn or pnp type, either power-switching or loudspeaker driving, it should be easy to work out an equivalent from your spares box.

Edit: I think TX coil is about 850 microhenry, so I calculate that C7 should be 470 nF to tune the coil to 7.8 kHz.

[ivconic]

It looks to have some similarities to the Fisher F2, which I've worked on.
The operating freq is 7.8 kHz. The coils are the same as the Fisher F5 / Teknetics Omega/Delta etc / G2 / Fisher GoldBug Pro , just a TX coil, no internal capacitance. The tuning cap is C7, that pale green one. The one next to it, yellow C4 is part of the pre-amp. This is a regular non-inverting opamp stage, with C4 and a low-value resistor ( under 200 Ohms ) in series going to ground.
The missing electrolytic is probably 47 microfarad , part of the power-on off circuit, or just general decoupling.
I have no idea about Q3, but it is probably an ordinary npn or pnp type, either power-switching or loudspeaker driving, it should be easy to work out an equivalent from your spares box.
Edit: I think TX coil is about 850 microhenry, so I calculate that C7 should be 470 nF to tune the coil to 7.8 kHz.

"...no idea about Q3, but it is probably an ordinary npn or pnp type, either power-switching or loudspeaker driving..."
Probably loudspeaker driving (or supporting), since audio is low level and distorted.
I have brand new, never used, Bounty Hunter 26cm coil. With 220nF inside. I was hoping to match that coil with this machine.
But now you gave me info and i see it is wrong idea probably.
Thanks for joining and for infos you posted!

[Skippy]

It is possible that Q3 and Q5 are the same part. Maybe you can see if any of the markings match up ? Test Q5, see if it is npn, pnp, or possibly n-Mosfet. If you are not using the backlight, just try moving Q5 to Q3 location.

[ivconic]

It is possible that Q3 and Q5 are the same part. Maybe you can see if any of the markings match up ? Test Q5, see if it is npn, pnp, or possibly n-Mosfet. If you are not using the backlight, just try moving Q5 to Q3 location.

I can't be sure, Q3 is blown and particles of it chirping on touching.
Label faded away.
I sent Carl a email asking him to give me at least those few infos.
Knowing him; he will answer in several days... or never!

[ivconic]

It is possible that Q3 and Q5 are the same part. Maybe you can see if any of the markings match up ? Test Q5, see if it is npn, pnp, or possibly n-Mosfet. If you are not using the backlight, just try moving Q5 to Q3 location.

It appears to be high current pnp transistor. (tribute to friend who give me help and hint!)
Closest i have is BC640, so i put it there.
Also put missing 470uF Alu cap.
All the damage was caused by the bad speaker.
It shows resistance alright but it sounds awful with terrible distortion.
So i tossed it. New one will be used.
I hooked up Bounty Hunter 26cm coil that i had already.
It is working, not splendid, because previous "servicer" messed up with front end caps.
I will additionally have to distinguish most proper ones to match this coil.
Air "depths" are not breathe taking, yet not that bad too.
I also discovered that small trimmer bellow COG display is actually a GEB!
Fantastic!
Only thing that i didn't finish completely are buttons wirements.
With use of old proven "fingering" method; i found out Menu, Up and Down buttons.
I am not sure about power On/Off ("fingering" randomly i manage to switch it On and Off) and whats more important; the PP mode.
I can't put it in PP mode so far.
Youtube regularly mess up my videos, so you can hear too sharp and somewhat "chirpy" audio on this video.
In reality audio is splendid, smooth and pleasant, as it should be.

[ivconic]

[Skippy]

On my Fisher F2, the membrane switches are very simple connections, not multiplexed X-Y or similar. Just two wires of the flexi-ribbon are connected to 0V ground, then a seperate wire for each switch. The switch 'closed' resistance was quite high, about 100 Ohms.

[ivconic]

In meantime i discovered this:

[ivconic]

[ivconic]

Finished, packed.
I put micro buttons below the sticker.
I also tried to trim it to work better by replacing 2 main capacitors at frontends
Originally both were 470nF.
Now is 470nF at TX and 120nf at RX.
Works best from all other combinations that i tried.
Since i don't have original coil but 26cm for some Bounty Hunter.
No matter what i do; i can't improve air "depths" which are modest.
Large coin at 22cm barely to 25cm.
Smaller Roman coins barely over 10cm.
Ferritte rod is totally rejected by GEB trimer.
Even if i lose a bit the GEB trimmer; i get no improvements in "depths".
Several strange and funny things i noticed at this machine.
It can not remember the setups.
If i adjust Sense to 10, Disc to 20, Volume to 3; it will remember those as long as is ON.
Once i power it OFF and than a while power it ON again; it returns back to default values?
One would expect it to keep previous values.
Why is that so Carl?
Next; in PP mode after i release button: it displays some letters "t" than "d" or something like that.
Why? What is the meaning of that?
Why it not stays at PP mode on one button press and on another button press to exits PP mode?
Why it displays "25cm" when PP pressed?
I peeked inside the circuitry and i see anything but trivial design.
On contrary i see delicate and complex design inside. I like what i see, other words.
I wonder why then it is not performing any better?
Aha! One more thing; At default Volume is too loud!
So i adjust it to "3" and than audio of detection is not that loud any more, it is fine.
But button sounds remains loud as previously??? Ha, ha, ha!
Why is that so Carl?
Unfinished project?
I am sure this circuitry can perform much much better.
I suspect that something is purposely "locked" inside the firmware to limit the performances.
No matter how i do really like this design; it's performing is disappointing.
Carl... you Americans; can't you obtain handful of ancient Roman coins, different sizes, and test your machines with them?
Detection and performances on such targets is whats count here in Europe.
Huge fat coins from pure alloys are not our common targets here... as is situation there in USA.
I feel sorry to see machine like this one, so good made, yet with such handicap that can not perform better on our common targets here.
Don't wonder why XP rulez here.
I will gladly offer my full support to you guys, anything that i can do; to help you to make your machines better than this.
Just address to me and tell me what do you need.

[ivconic]

Blast!
Nobody pointed me to read the manual!
It can memorize adjustment!!!

[ivconic]

Now...
here is a useful tip for all those having Teknetics Eurotek or Eurotek Pro and some of newer and larger Bounty Hunter coil.
Open Eurotec and simply remove marked capacitor from the pcb.


Than Eurotek will have up to 30% better performances with BH coil (and probably better than with stock coil).
Why is that so?
BH coils are having hidden capacitor poured in epoxy, assumable 220nF (can't be sure).
I did that and i got now pretty decent performances.
"Fat" coin over 30cm in air, Roman coin over 24cm in air. Iron pliers over 35-40cm in air.
Coffee tin can over 50cm in air.
Phase is on right place, no reaction on ferrite rod nor old Roman brick.
Of course there is certain amount of masking when detection occurs through the Roman brick used as obstacle.
VDI numbers generally falls for 20 points relating to genuine ones.
For example; "fat" coin gives 84 and through the Roman brick it falls to 62.
Roman coin smaller diameter gives 64 and through the Roman brick falls to 38-40.
Etc.
Not bad at all!
Because majority of middle and low class lookalike detectors; in such case will suffer from total masking, always giving "Iron" as result, or VDI 00 to 01.
Not bad at all!
I experimented a lot last couple days and i think this is absolute maximum that can be done with Eurotek Pro and this 26cm BH coil.

[Nandor]

yet again a nice post from you to read!

Thank you for sharing your work, it's performing pretty well.