TGSL Tuning & troubleshooting

[sdesic]

By moving coild made this ...
at this point md starts to beep ... cant stop it by pots

gb at middle

[golfnut]

Used TX and pin7 on X-Y graph
made it pretty adjusted phase so few lines are drawn ... I think
as I don't know what I am doing
GB on max (down)
K1 and K2 connected
[ATTACH]25102[/ATTACH]

Looks like something is oscillating
Should be an ellipse - the angle of it depending on phase shift between disc and Geb gating signals.
S

[sdesic]

What to do next ?

[Davor]

The first graph indicates a phase shift between Rx and Tx, and according to the X-Y plot it is over the recommended maximum ~20°. I'd say the Rx coil is too close to resonance, and reducing a parallel capacitor would reduce the angle between them. The Lissajous curves are quite useful for measuring phase between two signal sources. I can conclude, by fitting your curve with mine, and stereoscopic visual inspection, that your Tx/Rx angle is 23°.
See for yourself...

[sdesic]

that screenshot is not my nulled position - or we should quit that for now
after that I made one more screenshot (moving coils to point where it should be)

my first capacitor in RX is 15nF
I can desolder him and check capacity with LRC meter and confirm with regular multimeter and then ... replace with lower capacity
I have 1nF and 10nF in that range

[Davor]

that screenshot is not my nulled position...

It doesn't matter, the phase shift is largely independent of everything else. Only resonance offset and loading can shift the phase.

[sdesic]

15nF changed with 10nF ceramic
X-Y graph

don't see any change - maybe it shifted little bit to positive section

[sdesic]

Changed capacitor 10nF to 1nF and still I have same problems with coils at "nulling position"
detector goes beep beep beep ...

I tried moving coils and I can inverse or level this graph as I want ...
as I move them to nulling position RX falls off

[Davor]

Increased phase shift with reduced capacitance is confusing.

Can you achieve under 100mV at pin 7 in balance?

[sdesic]

started 4.5V AC and got to 40mV AC
barely made it... it was harder to find this spot with this capacitor value in place (1nF)

[Davor]

1nF is too small. Try with 10nF and see if you can ground balance your device. You know, find a piece of ferrite and wave in front of your coil, while trying to silence the response with GB pot.

[sdesic]

Replaced capacitor to 10nF... nulled coils at 45-50mV
detector starts to beep when I get close to that position and keeps going untill I turn it off
GB on min. stops it for few seconds
tried turning it but with no help

stops only if I bend coils from that position
sens pot is on min. or close to it but it doesn't matter if he is on max or min.

[sdesic]

Disconnected coils from each other and placed them in bigger overlap so it doesn't overload and start beeping
tried to wave with ferrite ring 3.2 cm and I can't set trimmer to eliminate it
it comes close to it ... eliminates it close to min. GB but it lasts only 5 s and then it beeps again

[Davor]

Can you trace the signal from audio output back to the source of beeping?

[sdesic]

beeps came from either detection of metal or overload / over oscillation of some kind when I place coils close - nulling position
there is no constant beeping when coils are 3 cm apart - overlap
less detection - less depth but then detector can be controlled with sens pot - other pot is no use anyway

how can I trace signal from audio part to beginning ?
check with "scope" on test points ?