TESORO GOLDEN SABRE

[cristiano.sar]

Sorry, I meant the regulated V+ at the LM7808 output pin 3 (should be +8 Volts) and the negative supply rail (from Diode D6 and Capacitor C5, should be about -5 to -6.5 Volts).

Easiest place to check is the V+ and V- pins of the IC's, see the schematics. They should all (except CD4024) show +8 volts on the V+ pin and approx -5 to -6.5 volts on the V- pin.

If your V+ and V- "rails" are correct voltage, let's concentrate on your oscillator section (TR1, C1, C2, R1, R2, R3). Something seems wrong there. Make sure values of parts are correct and transistor working OK -- I guess you already did that somewhat.

It is also possible something is draining current from your oscillator, like a solder bridge between traces. Check the resistance from J1-1 (same as TR1 collector) to ground. It should be really high, mine measured over 2 Meg.

If you have any extra coil approx 6 mH, disconnect your TX/RX coils and just connect the extra coil directly to oscillator and measure voltage. If possible disconnect the cable also. This is just in case you have some wiring problem in your cable or TX/RX coils.

Regards,

-SB

I'm having a similar problem.
Positive voltage: +7.97v, negative voltage: -6.37v.
My TGSL TX amplitude is around 10v, checked the resistance of J1-1 to ground with the TX coil disconnected and it measures about 0.7 Meg, should I worry about?
Thanks.

[Justihnno]

Hello! Has anyone simulated the circuit in Orcad and can they please help me with it?

[mostafalesnar91]

https://m.youtube.com/watch?v=lVrwQNLVg98

[mostafalesnar91]

there is a way to balance by ferrite ring (offer by russian). take the ring and put in center of coil.
input in it a wire of TX coil and a wire of RX one. you must seek up optimal number of the turns and their direction.
i have his pic somewhere but can not find right now.

I followed qiazhi's advice, I balanced the coil to remove the ferrite!!!here is noise in this film in the home environment, otherwise the device works fine, I just can't remove the foil with the disc volume.

[kt315]

there is a way to balance by ferrite ring (offer by russian). take the ring and put in center of coil.
input in it a wire of TX coil and a wire of RX one. you must seek up optimal number of the turns and their direction.
i have his pic somewhere but can not find right now.

[mostafalesnar91]

expected... now a good time to throw out first coil and to make second.
i noticed you do not want to hear suggestions. your ears seems covered by wax.

The ferrite is rejected and disc mode works fine so I'm on the right way!!!

[kt315]

expected... now a good time to throw out first coil and to make second.
i noticed you do not want to hear suggestions. your ears seems covered by wax.

[mostafalesnar91]

Can I assume you did get the coil and GB adjustments to work as expected?

I do recommend NOT fully encasing the straight sections of one coil. The resin can change dimensions when curing and move the coils.
Use clay to create a dam along one coil's straight section to allow finial adjustment. Recheck then tack into place. Recheck before final resin pour.

my coil test!
not good

https://m.youtube.com/shorts/jcVYypH2Pf8

[kt315]

Nautilus used preamp on RX coil, first. perhaps ML copied this way i do not know.

[dbanner]

Nautilus metal detector used this feedback method for fine balancing of coils.
One trimmer pot for amplitude and other trimmer pot for phase. This circuit can be wired up permanently inside the main box of the metal detector at the coil connector.

[kt315]

garrett coil sch

[kt315]

Can I assume you did get the coil and GB adjustments to work as expected?

I do recommend NOT fully encasing the straight sections of one coil. The resin can change dimensions when curing and move the coils.
Use clay to create a dam along one coil's straight section to allow finial adjustment. Recheck then tack into place. Recheck before final resin pour.

i do recommend Ivan Kostin sch that he used repairing garrett coil. simple and good way to tune.

[waltr]

RESIN TIME!!![ATTACH]58146[/ATTACH]

Can I assume you did get the coil and GB adjustments to work as expected?

I do recommend NOT fully encasing the straight sections of one coil. The resin can change dimensions when curing and move the coils.
Use clay to create a dam along one coil's straight section to allow finial adjustment. Recheck then tack into place. Recheck before final resin pour.

[mostafalesnar91]

RESIN TIME!!!

[mostafalesnar91]

Somewhere on this forum is info about adjustment of GB and silver detection.
If the GB adjustment is turned TOO FAR it reduces the sensitivity to Silver.
I did see this when setting up GB on the TGSL I built.
The GB adjustment is very, very touchy. If response to silver decreases then GB turned too much, turn it back barely a hair.

The TGSL calls for a single turn trim pot for GB adjust. If I rebuild it this will be replaced with a multi-turn trim pot to make GB adjustment a bit easier.

You can also play with the coil null/phase adjustment some more. Make a very tiny tweak of the coils then back to GB adjust with ferrite and silver.
If it gets worse then tweak coils in opposite direction and readjust GB with ferrite and silver.

Last step for GB adjustment check is out on real earth.

thanks!
I will try harder today! I must succeed