lobo improved

[maxbiri]

Hi all

Here are two pdf design i do starting from L.W. schematic, i try same little improvements, at least i think do.
What do you think?
There are others improvements that i can incorpotare in schematic?

Best regards
Maxbiri

[maxbiri]

Here is a revision

Because i dont like lm392, it will cause proplems in pcb layout, I change lm 393 and comparator of lm 392 with a lm339.
Ok now i have a unused comparator.
I change lm392's operational with half lm358 and again have a unused operational.
With this change i hope have a better pcb layout whitout tracks goining from one side to other side of pcb.
I know that leave input of unused operational floating is not a good idea, what is better? connect all input and output to ground?

Thanks in advant

Bye Max

[amtech2005]

lobo improoved

Excellent Work !!! You know that you picked a "Great Detector" to work on !! I read the field test's on this detector and it was designed for small Gold nugget's but with the right search coil , the Lobo also work's excellent to find Old-Coins very "Deep" . Thank-You ...........Eugene

[maxbiri]

THere isn't any hint or critique abuot schematic i posted?
If so i will start design pcb, the more time consuming part in a pcb.
I'm looking for a photo of front panel, lobo classic not supertrack!
I need better understand the function of all swichs.

Bye Maxbiri

[amtech2005]

Lobo improoved

Hello again , Maxbiri. I looked at the last pdf schematic you posted again . Two things I noticed , 1. What is the capacitor network of "8 Caps" doing in the upper left of the schematic ? Are they for all the I.C.s ?? and 2. Did you complete all the power supply voltage connection's ? I will look at your schematic again tonight. This is a Great detector and I will try to find some close-up photo's of the original Lobo but it won't be easy !!!.....Good work you have done so far !!!! Also a week ago or so I read from another member's post about the LS204 chip , Are they almost obsolete/discontinued ??...Does the LS204 have a lot of noise ?? Maybe you should search for a better replacment ?? ...........Thanks..........Eugene

[amtech2005]

lobo improoved

Maxbiri , the older the metal detector the harder it is to find a decent photo !!! Remember the "Original Lobo" was 20 khz. The new Lobo ST is around 17.5 khz......You can see the difference in the switches and the potetiometer to the left ...This should help a little....take care....Eugene

[maxbiri]

Hi Amtech2005
Yes the net capacitors is for decoupling all ic, same decoupling capacitors i designed near IC and other are in the net for better readable.
Even for power nets i used net alias.
There are 2 or 4 decoupling capacitor that must be deleted because i incorporate lm393 and 392 in a single lm339.
Yesterday i start design pcb but looking at schematic and pcb i was thinking about same others improvements.

1) I remember that 7660 dont have a simmetrical negative output and it give a lot of noise, so maybe i will redesign the power supply stage.

2) May be we can drive the oscillator stage at battery power and not 8 v, iìm not sure but is possible we gain 1-2cm in detection range.

Yes LS are obsolete an difficult to find i plan use TL072 oe lf 353 but any hint about other ic are wellcome!

Bye Max

[porkluvr]

LS404 substitution

Yes LS are obsolete an difficult to find i plan use TL072 oe lf 353 but any hint about other ic are wellcome!

MC33178 dual, and MC33179 quad are very similar to the LS402 and LS404.
These have much lower noise than TL07x, and consume about 1/2 less power. MC3317x (and LS40x) also can swing their outputs closer to the supply rails, compared to TL07x.

I intend to use MC33178 for the two receive amplifiers, and maybe use MC33172 for the discriminate control phase shifter and the sensitivity control buffer. MC33172 is a relatively noisy amp, but it uses much less power than the MC33178. I think it will be OK because low noise is not so critical in those two circuits. MC33172 also has (almost) rail-to rail output, and sufficient speed.

Good luck with your PCB. I have one in the works - planning to convert my Silver Sabre II into a LOBO. The power supply circuit is being reworked because my SSII cabinet only holds two 9V batteries. I will have a seperate power board mounted over the signal board and probably use a LT1615 low power switching regulator. The switching regulator is giving me headaches, (trying to get the most power-efficient configuration) but I think it will be worthwhile. My battery low circuit will be an LED flasher instead of audio.

[strujas]

Hey guys look at this, Lobo is high rated!

[Max]

Hey guys look at this, Lobo is high rated!

Hi,
you must consider that Lobo have standard coil 10'' DD... so the gain in depth is partially due to coil employed respect to e.g. eldorado.

Sure is a good one by tesoro... but coil is important too in such considerations.

I mean they are all similar about e.g. TX stage, power... and components employed so the depth is about the same for same coil type and dimensions... I think TGS has exactly same power of Lobo, but cause Tesoro sold it for other purposes (nugget hunting mainly) it was discredited as low depth capable... though there isn't really... just you need proper coil for it.

Just my 5cents

Kind regards,
Max

[maxbiri]

I Max

I'm agree with you about standard lobo's coil, so may be that the test is a little falsed.
More or less all tesoro schematic are similar but i think that lobo is a little different.
Tx stage is forced by 555 and not a pure LC oscillator as in silver, eldorado ecc ecc.
The tx stage is equal at diablo or similar at fisher 1280-1266 ecc ecc.
tx F is 20 khz and not around 10 khz as other tesoro's device.
Filter stage look as all other tesoro design with little difference.
I like thery much eldorado and it's discrinating power and power line immunity.
From lobo i aspect same power as eldorado but a better sensibilty to small target.
On eldorado i have about 30 cm for 1 euro coin in air and disc mode.

Bye Maxbiri

[maxbiri]

Finally here is a pcb design for lobo rev1.
Not happy with this layout, too much bridge in terrible position and a very crowded pcb but this is the best i can do on single side.
I'm thinking about split circuit in 2 pcb, one with only tx stage, power section and audio stage and second pcb with only rx and filters stage.

[sirkut]

I may have to give this pcb a try. Thanks!

[aft_72005]

Finally here is a pcb design for lobo rev1.

Hi maxbiri
You are working very good and fast . are you build and test your lobo PCB?
Best Regards.

[maxbiri]

Hi AFT

No, i havent built and tested, as i said i 'm not happy whit it and i would likel split design into 2 pcb , i need find time for these new project!

Bye Max