RELIC HAWK

[Max]

I belive this design is meant to have the coil slightly off of null. This is forced by the feed of the TX through the 4 Meg resistor. I believe (but not sure) that the RX coil is supposed to be nulled by viewing the output of the preamp. This would slightly bias the RX coil signal to provide a better S/N from the coil (never let it really be nulled to 0). This may ever so slightly also increase the area of the DD overlap, increasing the width RX field.

Regards,
J. L. King

Hi JL,
probably you're right... I think the same.

Now my readings about signals from the circuit running at 5Khz, considering TX as reference.

With geb knob fully counter-clock-wise GEB control gate pulse (positive) start after 79.2° from TX start. It ends at about 260.4°.
With geb knob full clock-wise I get pulse (positive) start at 97.2° and ends at 277.2°.

About disc, with knob fully CCW I get 124.4° as start and 303.6° at end.
With knob fully CW I get 248° at start and end is at 428°. This at one extreme of geb pot... is different from simulation ?

I checked your simulation and seems all fit about geb ... about in expected ranges, but disc I don't understand...I read from 124 to 248° as start at one geb extreme...I cannot see that in simulation.

Is there maybe some mistake in disc section ?

Kind regards,
Max

[Max]

Eclipse,can you make two better pictures from the total board,top and bottum side or can you trace the F line ?It is hard to do with this pictures.Grt Nakky.

Hi Nakky,
I think you found it.

I was following it... just under the smd resistor there and found your post that let me think you found it already.

Now we have to consider the 2nd comparator inside there... and look about where signal came from.

I mean... we have to look for disc or geb related control signal.

Kind regards,
Max

[nakky]

Max,look at this.

[Max]

Hi,
I think the mistery is solved now.
The "f" goes to pin5 of an LM393, then the pin6 ...where's inverting input goes to a 18K resistor: it's GEB control line, cause just GEB comparator take input at that 18K = out pin of previous op amp (U6 on our schematic).

So Minelab bind "f" line at GEB control signal, not on DISC as we have in our schematic.

Do you agree ?

If ok and no questions I will put in next revision.

Kind regards,
Max

[KingJL]

I checked your simulation and seems all fit about geb ... about in expected ranges, but disc I don't understand...I read from 124 to 248° as start at one geb extreme...I cannot see that in simulation.

Check both ends of R5 in the asc schematic. That is equivalent to min/max (or max/min) of disc. Actually it is pretty slick ,the way they arrive at DISC delay.

Is there maybe some mistake in disc section ?

I don't think so. Remember there is really a 180 degree phase shift from the signals at R5 vs GEB as seen by the phase detector (GEB to inverting, DISC to non-inverting). I think that results at ~(-42 to -314) /~(-67 to -297). The 2 ranges on each side of '/' are for the 2 extreme settings of GEB.

Regards,
J. L. King

[Fred]

Hi Max,

Yes we can say for sure that it goes to pin 1 of 393, so there was a mistake when shematic was traced pin 5 and 6 were mixed, wich is very easy to happen.

Nice team work, an congrats to Max who found this before.
In fact the "problem" with ferrite looks like a proof that it really works,thanks to the manual.
Regards,
Fred,still waiting for parts

[Max]

Hi Max,

Yes we can say for sure that it goes to pin 1 of 393, so there was a mistake when shematic was traced pin 5 and 6 were mixed, wich is very easy to happen.

Nice team work, an congrats to Max who found this before.
In fact the "problem" with ferrite looks like a proof that it really works,thanks to the manual.
Regards,
Fred,still waiting for parts

Hi Fred,
well, yes I like all this team working here... very nice and productive!

Now I have to focus about solving the geb stranges... using a better... 10turns pot... and see what happens... if I can null with it on ferrite we'll be sure GEB works also in all-metal, so that it works REALLY.

Also the other problem is at disc phase shift... I see different on scope vs simulation... must understand why.

Kind regards,
Max

[nakky]

I can't see it ,is it pin 5 or pin1 ?

[Fred]

I can't see it ,is it pin 5 or pin1 ?

Hi nakky
If you look carefully you will see the "9" of lm393 so you know the position.
You can also see the notch designed in white below the IC.
regards,
Fred.

[Max]

I can't see it ,is it pin 5 or pin1 ?

Where the f goes ? now I think it's pin1 for me... but maybe not

if not... then is pin5.

It's not really a problem... let me explain:

if is pin5 then the input is at pin6 (inverting) and goes to 18K
if is pin1 then the input is at pin2 (inverting) and goes to 18K

both ways the comparator inside see 18K at its invertin pin... that's what we are looking for to say it's GEB related.

BTW, Fred is right, I agree on the 9 and notch.

Kind regards,
Max

[KingJL]

Check both ends of R5 in the asc schematic. That is equivalent to min/max (or max/min) of disc. Actually it is pretty slick ,the way they arrive at DISC delay.

Sorry Max, I had changed the asc before I sent to you. R9 in asc should be 10k. Check both ends of R9 NOT R5. Everything else is the same. Sorry for the mistake that I sent you!!!

Regards,
J. L. King

[Max]

Sorry Max, I had changed the asc before I sent to you. R9 in asc should be 10k. Check both ends of R9 NOT R5. Everything else is the same. Sorry for the mistake that I sent you!!!

Regards,
J. L. King

Hi,
no problems I saw it... changed to 10K.

Thanks again,
Max

[nakky]

[Max]

No dubt... it's pin1!

[KingJL]

About disc, with knob fully CCW I get 124.4° as start and 303.6° at end.
With knob fully CW I get 248° at start and end is at 428°. This at one extreme of geb pot... is different from simulation ?

124 to 248 = 304 to 428 (really 60) when you take into account 180 phase shift from GEB. Now when shift 90 degrees to get center you have:
-30 to 214
Simulation results (adjusted for 180 difference between GEB and DISC and then 90 degree to center of gate):
GEB -12 to 7.5
DISC -30 to 210 @ -12 GEB, -43 to 228 @ 7.5 GEB

Regards,
J. L. King