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Originally posted by Unregistered
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I think is a quad comparator: LM339 -
Thanks MaxComment
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Hello Forum ,
My simple thinking is first determining if the schematic is good , if is good next step is draw a prototyping printed circuit , I think it is not so important to copy exactly the board of Mlab, because this board is sure make for AUTOMATIC placements of components , not so for the inter modulating problem!!!
I prefer the design board of TESORO it is like hand draw with very thin curve line not straight line, i do not know what program they use???(see the board of GS) and to experiment with the CI it is better to mount low gold support Ci and make test....
For the so 27M4 etc... Thirst thank you Max for your very good work , i suggest I am not so sure that this Ic are much... much better than a TL064 ... in my idea , minelab buy bulk of so much industrial ic's for different department developing military detector etc... they use what they have in stock...
I think that because in a electronic design You have two basic way , first the standart with commun ic's and second the military o pro industrial design with all COMPONENTS IN THIS WAY .....Because if you mix standart and ultra tech ic it is not logical ... one?s kill another's specification.... so If they put the standart mixer 4053 they use also standart ic Tl ...etc... and front end 5534...
I was experimenting with the audio configuration of RH , work very well the 15mH choke is not a filter... it is use to boost and make a little wow innnnnnnnn at the final of the sound like a burst... I will incorporate this in my PI sound board because it is good and original idea.I make experiment with 20 mH and 47 mH work very well also... So the audio out system of the RH is a working schematic good.
Thank all guys for the geotech forum so good
AlexisComment
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Alexismex, i am also interesting in this audio stage. What TGSL really lacks is audio you explained! Have you managed to skip earphone using and apply this to use with 8ohm speaker? Only thing is to void that resistor, right?
Oh, one more thought;
in case applying this audio mod to TGSL, 2 of 3 transients from 4024 must be omited, i am almost sure about this.What do you think?Comment
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Hi Alexis,Originally posted by Alexismex View Post
well... most of things I agree. I don't agree that TL064 or TL074 is the same there as 27M2... the difference you could notice and could be heavy: I tested a lot on other VLF and the impact of a TL064 could be catastrophic on stability of circuit. This is expecially true at integrators in our case of RH.
The fact they used LM393, LM339, 4024, 4053... (very common and "normal" components) is not as indicative as the fact they used NE5534 at preamp.
NE5534, though today can make laugh people cause so low priced and easy to find, was very nice choice at that time about noise: 3.5nV/sqrt(Hz) @1Khz is not a casual number...
Now if you consider signal path you'll see there's a logic in using low noise preamp there along with other low noise / low power op. amps as integrators etc
Sure they are not military grade components... but RH is hobby-MD not mine detector... so I think they used good compromise between costs, availability and performances for that time and purpose, and was good choice.
The fact there are mixed common components with something a bit more "quiet" is sign they noticed great improvement using that "special" parts in that places. If they had already a big stock I don't know... probably is, but I think this couldn't be really a reason when a single unit costs so much having 20-30$ more production cost. Yes, will be 20000-30000$ more production costs on 1000 detectors made but I think this is not a problem for company like ML, expecially for their marketing department, "selling" (actually fixing "target price") an MD for a bunch of dollars more...when unit costs already some thoiusands dollars
, cause brand make the difference. If someone have to spend 20$ more for a bad chinese MD he will consider don't buy at all... but if he wanna a top of the range ML MD I think he will spend 100-200$ more without asking why and will be proud of that at the end if the MD is good as expected! 
It's like when you have to buy a car: if you buy a (for example) SKODA... well... any cent more could make you change idea...
but if have to buy a FERRARI you'll WANNA SPEND MORE to say to the world you're a winner and meet with miss college...etc 
Capitalism paradoxes ? Or just that any TH want in his hands the best MD on the planet... cause he actually buy a dream not only a box filled with components! 
Just my idea of course...
Sure there's also room for improvement on components over original RH stuff, expecially today that costs of many (good) of them is so low. But I think this could be further step after replicating a good working clone.
Kind regards,
MaxComment
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RH
Hi Max,like this.Comment
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Like thisComment
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Hi,Originally posted by nakky View PostLike this
yes like this!
27L4 is the lower power version of it...
Kind regards,
MaxComment
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Hi,
this is rev1.1 of schematic: added power rails and pins to ics
Now notice there are 13 ic, and 26 decoupling capacitors (not reported on schematic all but indicated with the box in the middle that say "U1-U13"...):
decoupling are very close to each supply pin at every ic, one on positive pin and other on negative one.
They are to prevent spurious signals propagate by power rails from one stage to the other. Value = 100nF each
Kind regards,
MaxComment
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Hi
Max.
I meaned this part.
Exelent work with the schematic.This is progress for shore.Comment
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RH
Hi Max,look at hand draw RH schematic,I think U11 must be LM339.Grt Nakky.Comment
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Hi Max,
I can try to work on a PCB when you think everything is clear enought ,the diagram is 100% OK and that this detector is worth it.
Let me know!
Regards,
Fred.Comment
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About that choke....
as i remeber pins goes like this (bottom view)...
Comment
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Hi,
Hi,
Ivconic.
Did you mean this red box on the picture?
Because I have looked coinseeker so much I were thinking that 15mH choke is paralel with RX.
So if this is choke moment can we just use 15mH and 60mH small like resistor looking and wire them same way?Or I have to look for this one that will be harder to find.
ThanksComment
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