Jump to content

Lobo Exp

  • Content Count

  • Joined

  • Last visited

 Content Type 


Detector Prospector Magazine

Detector Database



Posts posted by Lobo Exp

  1. On 3/29/2021 at 10:30 AM, Rick N. MI said:

    This is photo of what my circuit board looked like on the Lobo ST.

    The pot circled in red is the ground balance pot. The one next to it is a disc pot. 

    On mine I marked the ground balance pot before I turned it counter clockwise. I turned it a little less than 1/2 way. In my mild ground with the 8" concentric coil it would hit my 10" test dime.

    Lobo st.jpg

    Thing is with this model the board is most likely a multiple layer which makes it even harder to reverse trace the circuitry. The Russian clone model on Ebay is only a 2 layer, conductors on both sides and nothing in between with a laminated board. It's a big enough mess by itself and for sure this model is way beyond that. Is this a replacement board or was it removed by unsoldering the leads? It appears to be a new board with no solder in the J points, so there must be some instructions lit for it. If so, it would be a big help to Trisha providing her board isn't toast now. I would like to know as much as could be provided about this detector just for my own benefit and for others. 

  2. On 3/29/2021 at 10:28 AM, Steve Herschbach said:

    If there is anyone out there with a Lobo ST, it appears there is a need for a good, clear set of circuit board photos, that can then be marked up with notes. There are bits and pieces of info scattered about, but I’ve not found a clearly noted Lobo circuit photo despite some time with Google.

    Tesoro Lobo ST Data & Reviews

    For sure on that! A schematic would be a life saver. I could draw one up but it would take a fair bit of time to do it. I just don't have one to reverse engineer. Trouble is with the ST is what I have seen as at current here in the photo posted, they are SMD which makes it tougher to do. I have attempted to track down this info myself and spent a good amount of time to come up with NOTHING yet. Someone has to have this info but finding out who is the deal and it would probably require a subscription fee to access that info. I used to have that kind of access years ago when I was doing repair work on electronics, I gave that up because a lot of the time it cost more to fix stuff then it did to replace it. The ST has a bunch of additional circuitry for the auto track which has made it much more complicated, and the parts are much smaller too, things are a lot more crowded on the board. 

    • Like 1
  3. Pots inside the housing on the board are for tuning the detectors frequency, discrim,  rough ground balance, amplitude, and then there are the volume, fine ground balance, external discrim, sensitivity and threshold on the panel. The ST has a momentary push button on the handle a think for resetting the GB. I think it can be used in auto or manual GB by setting a switch on the panel too. If the photo posted of the circuit board is of a ST, I see 9 pots, and no one has a schematic of that detector or has found one and posted it that I know of, so I can't say exactly what each one does. The photo doesn't show any masking with text to indicate component specifics as to what pots are for whatever function. The only way I know of to do that would be to identify each IC and track down the tech sheets on them to figure out what purpose they serve in the circuitry, very hard to do specifically. Reverse engineering the detector board would take a long time and a lot of detailed work. Since Tesoro has gone away, I suppose it is possible to find someone that has worked for them or on them and has a schematic which would answer most of all questions. As it has been stated, to mess with them will render the detector useless which is why most of the time they have some type of glue placed on them to keep them from being adjusted, adjustment requires an Osciliscope and knowing the specifications of the detectors frequency and other specifications. 

    • Like 2
  4. Ok  I just came back to this post and from looking at the photo, which is kind of hard to go by, you basically have 3 colors of wire, Red, Black and White, I'm going to go out on a limb and state this, most of the Black wires are going to go to a ground point. If you look at the wires going to the dials, these are what are variable voltage dividers for adjusting the detector circuitry. Black wires should go to a ground, red wires are going to go to various points of the board that supply the positive side of the power in the circuitry. The white wires go to the circuit points that are classified as signal returns, these are positive voltages of variable levels. There are 2 green wires, I see, one goes to the speaker and the other goes to the detector coil  connector.  I see that on the dial/ pot on the left has 2 levels, one has 3 wires and the other only 2, a red and a black. The red is a larger wire than the others and it looks like there is an issue with it at the terminal. I am going to say since the other wire next to it is black, there should be a black wire next to it. There is another larger wire than the others which is black, is connected to the board. Someone else mentioned they thought the colors are reversed and I am inclined to agree. The fact that there is a little noise when the batteries are connected bothers me. Circuits like this are very sensitive to the correct polarity, and it is very common and preferable to switch the negative side of the batteries on and off since by doing this, it is much less likely to cause component failure. You see, by switching the positive side, there are what is called transient voltage spikes which raise havoc with sensitive Integrated Circuits, the large black chips on the board. Reverse polarity can and will destroy these and other components on the board!  I hate to say it but it may be a moot point to try to revive this detector. By leaving the red or positive lead connected to the board at all times and switching the negative lead on and off there are no voltage spikes which could burn out the chips. I mentioned polarity protection in my last post and if there is some protection circuitry it may very well be a salvageable detector, only one way to find out really, remove the red and black wire and correct the connections then try it. However as I stated earlier since there is a noise, I am going to say there is not any protection circuitry, if there were, there should not be ANY noise at any time because the protection circuit would stop power from flowing completely into the circuit! I'm going to say the noise is a clicking sound briefly and then nothing. NOT good as that would be the sound heard from the speaker due to many shorted circuits within the circuitry, just the speaker clicking and then nothing as sound from a speaker is supposed to be alternating voltages. Again, I think you have a pretty much useless compilation of parts now. For what its worth, it is not un repairable, but the cost is going to be above and beyond the cost of a replacement, likely. Someone like myself could and would attempt to tackle such a task by using special meters and a power supply which would limit current draw fed to the board and remove various components along the path of power one at a time and determine which one is shorted and work through the schematic testing it. The real issue is with these SMD style circuits is they are a pain to work on. The parts are so small and can be damaged by heat trying to remove them, they may not be defective to start with but become defective before it is fixed. 

    • Like 1
  5. I saw that, 4 or 5 pin arrangement. I finally found my way to MetalDetector.com yesterday evening and looked at what they have to offer and found several coils that are listed to work with Tesoro models compatible with each other. The prices are not too bad considering what they run for some other Detectors/brands. I don't have a problem with paying $150 give or take $50 for a piece if it's right and since I am not an experienced prospector, (yet) Haha, I only need to lay out the cash for just one coil to start with and make sure my project is even going to work. If and once I get to that point, I can work on another size. Start out with the cheaper unit, when I know I have a metal detector, go for the another unit. 

  6. I am looking someone that has extra or used coils that are still in decent condition. I am trying to build a detector from one of the Russian boards and will be needing a coil first for testing and later if the detector works, for hunting. It needs to be tuned to 17 to 18khz to work.  The coils for Tejons, Vaquero and Cibola and maybe other Tesoro models will function. I don't know that much about the models Tesoro sold and there doesn't seem to be much info on the net about such details. Coils seem to be hard to find for these units also. I have been searching and not finding much. I found one used Lobo with all the pieces on an auction but it found a home before I could make a run at it.  I looked at some non branded coils also but there wasn't enough info about them to determine if they would be suitable. 

  7. Well that sounds like a possible cold solder connection. Most of the time when something stops after it warms up it is a component issue. But working when it warms up, I would look for a bad connection first. If the board is assembled with lead free solder, it is more brittle than the older 60/40 lead tin stuff and can fracture at the joints. 

  8.  If you can post a photo of the side of the board with the traces, may be both sides have traces. I can tell you for certain if the photo is clear enough. I have a board for the old classic in kit form from across the Atlantic I am working on. There should be a Voltage regulator for the board, it has 3 large flat leads, the center lead is the negative terminal, also tied to the heat sink, which should lead to a wide trace that boarders the PCB. The black wire goes to the center lead. The red wire will go to the trace that leads to the end of a diode(opposite end from the white band if the diode is black) with no other traces going anywhere except to the diode unless there are wires going to the on/off switch. The diode will have a white band on one end which will lead to the regulator power in, the V reg has a heat sink tab with a hole. This part and the diode should be very close to each other. I have never seen a clear photo of an ST board but that shouldn't matter. The schematics for particular components sections are basically the same up to a point. The power supply design is a standard and the only thing that changes is placement and maybe a few extra components depending on how much polarity protection and filtering capacitors are included. The diode is there to keep from blowing out components in case the battery is connected backwards, which is usually pretty hard to do with polarized connections. It should be rated for at least 1 amp which is not much but that is in forward bias, reverse bias is much more.  However anything can be done if you try hard enough like putting the batteries in a holder backwards, it has been done before and touching the battery connector in reverse even for a split second will burn out the circuit parts. I know this gets to sounding like you may not know much about electronics from my end. I don't have any knowledge of how much you do know so I am trying to make this as clear as possible. Again, if you take a good close up photo of both sides of the circuit board it would be a big help but that may be a tough one with all the other wires on the board. You don't mention the model of the detector and schematics seem to be a hard thing to find most of the time for any of the detectors. If this helps, then your are set to repair your unit. 

    • Like 1
  9. Kind of what I thought too. I understand the old lobo is not top of the line in technical advancement by current standards and have been trying to find out how well people think the Lobo (not the ST) works.  I would like to find some boards for a more advanced detector to build. I haven't sold myself on one of the features of the ST, the auto discrim, but it has the option to choose auto or manual from what I have read. I would like to find some parts for some of the other models too, but haven't seen much. I'm of the opinion that the more dials and switches something has the better it works, maybe, sometimes more complicated is too complicated to use. The feature on the ST that needs to be reset frequently, Ground Balance, bugs me too. Maybe the Ground Balance is also selectable and I am off on the Discrim. auto/manual, I don't know now. Any how, I am about to a point on my project to move on to the mast and coil. I have a plastic project housing box that is half the height of the Aluminum housing shown in the photos online. I am going to use metalized tape on the inside for the shielding and common grounding for all the stuff that needs it. It may be a mistake, I don't know yet as there are still items I need to work on, like plug jacks and switches, etc., not planning on putting a loud speaker inside so that should make it easier to house. 

  10. On 6/18/2019 at 1:55 PM, Rivers rat said:

    Hi it was on a modded silver sabre 2 this machine has more knob and switch than anything.What i realise is when warm(no joke) it works ......plug the coil and try again to turn all knob and switch.I got 2 LOBO ST and the scream when turn ON to indicate the battery level.But i am unfamiliar with the original LOBO



    I just read something today about the audio battery indicator which I am assuming is a feature of the older units, has been replaced with the little LED placed in the central area of the PCB such as on the Russian Fed PCB offered on Ebay.  Since I never had any experience with any of these, I am anxious to get my board finished and tested. I do remember many years ago someone with a detector prospecting for coins and stuff in a local park. I was a still a young kid at the time,( like 40 or 50 years ago) it seems like the thing made so much noise I didn't understand how anyone could tell when they had actually found something. Also I am learning as I continue my build what all the dials and switches are for, this is to whom was asking about what they do. There are or should be the on/off switch, 2 other switches that are for tuning the metal discrimination and auto/ manual modes. There is a simplified wiring method that eliminates one of those switches. 

    • Like 1
  11. To Jeff Jones,,, I was wondering if you got rid of the controller you mentioned earlier? I have been working on one of those Russian Federation PCB's for a while now, a little here and there as I can get parts for it. I'm also looking for a coil that is tuned to the frequency this board is running at, 17,5khz. I may give a try at making my own coil, I have some enamel coated wire, but not sure if I have enough to make the coil. Making the form and getting the housing may turn out to be the hard part, getting the proper materials needed for it.

  12. I cannot say for positive on the issue of using a control box without the coil plugged, but I can say that with other circuits like 2 way radios, it is not a good idea to turn them on without the load coil which is what these machines are, transmitter/receivers. 2 way radios are meant to work with antennas tuned for a low standing wave ratio. Take CB's for instance, there are SWR meters for tuning the antenna length. Ideally you want a 1:1 SWR. Different frequency transmitters require different length antennas. Metal detectors work on the same principle. They send out a electromagnetic wave from one of the coils and the other picks up distortion in the wave shape when a metal object is within the field it generates. The metal object resonates its own field when the electrons in it are excited by the field from the control box signal sent out in the TX coil. So if there is no load sensed by the transmitter, the signal is fed back into the control box and the Integrated circuits are often very sensitive to load and reflected signal. Since that signal is supposed to be sent down a length of cable to a coil which is away from the control box, through a shielded cable lead no less. The coils are designed to have a certain impedance/resistance which changes with changing frequencies. I do know that the higher the power level, and frequency the more it can be a problem. I have been told it is not a good idea to turn on a Microwave oven with nothing inside or metal objects inside, they are high power and so, I think it would make sense not to turn on a small generator such as one of these detectors with nothing to absorb that power as well. 

  13. I forgot to mention a neat little piece of test gear that makes working with electronics much less hassle. The little GM328 transistor tester, which tests about every standard component one would work with. Transistors, MOSFET's, Capacitors, Resistors, Diodes, and Zeners up to 9 V, Inductors, and it identifies component leads and values. It will tell you what something is if you cannot identify it by the numbers or color code. Frankly I don't know how I got along without this device this long. It uses AVR C++ code running on a ATmega 328 controller with LCD display. The tester comes in kit or assembled, it is very cheaply priced for what it does. Get one just for the fun of having one, if you get one of the DSO's online plus your digital multimeter you have just about all you need for home hobby electronics.  

  14. I ordered one of the DSO kits and assembled it. I haven't  gotten it fully calibrated yet. There are some people that have posted Youtube videos about them and it seems replacing a few resistors in the circuit improves function and display for a cleaner wave pattern. I think I am going to order a second kit and assemble it with the suggested value which are 10x what the kit is supplied with. Also planning to order a kit form Function generator to work with setting up the scope and the detector. I also recently noticed that Digikey and possibly some other firms have done away with the minimum order. The big problem with electronics it seems prices for items within the borders of this country are higher priced than Chinese, freight, time for delivery, it all makes everything such a hassle. I use Ebay for a lot of stuff as it still turns out cheaper and I have no issues with using the Foreign parts. Some people try to tell us those parts are sub standard, However you must realize, very little is still being made in the U.S. and this is the kicker. Chinese parts are used in many Military Defense items. So in that context, I feel we have little to worry about if a component fails. Simply find the problem and repair it. If you have knowledge to build the machine, a Digital Meter and a logic tester should get the location of the issue pinpointed. Since the detector works @17.5khx and the DSO is supposed to work up to 200khz it should be good to go for calibrating the detector. People have said the DSO has issues above 20khz but the detector is below that. DSO kits are so cheap on Ebay I hardly see how or where one would be wasting time and money working with one. Besides that the kit is good experience and fun to assemble. I don't feel any piece of test equipment no matter how cheesy it seems to be is a waste, and there's nothing cheesy about the DSO kit or the detector boards from Ukraine/Russian Federation. I have searched and examined several of the detector kits, boards, ect. online and IMO with electronic circuits, the more complicated it appears, the more it does. The Lobo is very complicated with all the IC chips and components it uses. Note, with the unit I have been working on, there were a few of the R's that had very high values of which I did not have on hand and I had to use Ohms law and assemble with more R's than the instructions said. Most of the items I order over Ebay are assorted parts packs so I get a huge discount over just getting the exact items through Jameco or any other supplier and the things I can't find cheaper, go to them. Orders always hold back till I have a list that will pass the needed price to not be charged a sur charge.

    • Like 1
  15. Lobo Lover, you are discussing turning R33 and saying someone mentioned that moving it may be a bad idea. All of the pots which are on the board are supposed to be set with an Oscilloscope. if they get moved than the detector will be off frequency and likely not functional. I am still working on getting my board together, I recently purchased one of those kit form DSO scopes from Ebay and assembled it in hopes it will help me get my detector up and running. Also I got on this post a few months ago and it seems it has died? If anyone is still coming here, I would like to see what is happening and get up to date on these projects. 

    • Like 2
  16. KAC made mention of getting parts through Digikey but the issue of getting parts not in minimum bulk, there is a Company in Calif.. Jameco Electronics and they will supply many parts in any quantity you need, the only requirement is to purchase more than $20 or so or they hit you with a sur charge. They have a nice web page. I purchased one of the blank boards some time back and started putting it together then set it aside. I have more parts on the way to go a little further with it. They should be coming in any time now as of Feb. 20/21.. From what I read some time back, the coil used with this circuit is pretty specific and you likely won't be able to get another coil from a different circuit to work well connected to it unless it is a detector that works on the same frequency, impedance, I recently noticed more boards are being sold, I got an email the other day asking if I wanted any. I think I will order a few more of them and assemble them for passing along if anyone is looking for one. Only thing I need to work on now is building a coil. At least to use for testing. Then work on a case and handle. 

    • Like 1
  17. At least now you know what and where to go if it happens again. May start thinking about getting a new pot. They are not all that robust anyway. A small metal wiper running on a thin layer of carbon inside a none sealed housing that gets dust in it. There are pots made that are better housed and won't be easy to get trash in them. Everyone usually goes for the cheapest piece available to get it working long enough to sell and after that, well you know. throw it away and get another, that's the American way.

  18. Coils are supposed to be shielded from the housing all the way to the coil. I would start by looking for a place or connection from the shield to ground point in the circuit to be a cause. These things are supposed to be super sensitive so it wouldn't take much of a leak in the ground circuit to let interference into the system. Beyond that, as I just noticed in your later post about the pots, yep, that would be about the same as a component value shifting, it happens. Glad you found the gremlin.

  19. Ok I just joined this site earlier today and I am having issues getting where I want to go. I think I may have hijacked someones post and if this gets where I want it to go, I appologise. I just read a new post by KAJ asking if the circuit could be modified to run at a much higher frequency. I would like to tell him that I believe it could be set to run about anywhere provided the correct components where installed on the circuit board to enable the 7555 to generate the desired freq. simply by replacing the resistors and capacitor with the values needed to adjust the timing of the IC.

    • Like 1
  20. On 1/3/2019 at 5:14 AM, Lobo Lover said:

    Hello everyone, 

                               I have just joined up and this is my very first post. I'm surprised to see fellow detectorists here from New Zealand. I've been here in N.Z. for almost 12 years now and only bumped into one other detectorist just a little while ago, some newbie from Christchurch going back home after his first trip to    Kyeburn Diggings up Dansey's Pass. Some older dude with his new Gold Monster 1000, he stopped off at the beach here in Timaru for a snack and his afternoon nap. No luck for him this time and he was complaining about all the metal the old time miners chucked about there. That's along drive to about 2.5 Hrs one way. We were just heading home after hanging out there for the afternoon, when he saw us just after testing out my wife's new BH Commando TK4. So we had a little bit of a tail-gate meeting with him. He wanted to showed us his GM 1000, it was nice to have a look at one up close and I took it for a bit of spin in the dunes. 

    Anyway I'm not here to chat about new acquaintances, got much more important stuff to talk about. I would like to Hyper-Tune or Super-Tune my Lobo ST and  need some help with it. I Was thinking about putting on an external ground balance potentiometer to get some more depth, but first I need to know how it all works. Because my wife and I are Newbie's too and I'm trying to teach myself, my beautiful and talented assistant the "wife" all the ropes about MDing.

    So if anyone can help in anyway it would be very much appreciated.  A German guy did that to his Lobo and he seams to be happy with his mod I think his name is mschahl and another guy Keith they both seem to very knowledgeable about the Lobo ST.  I would love to here about what is and isn't, the up and down's, the in's and out's and what mod's I could do with these two MD's the Lobo and BH TK4.

    Also I could get a new PCB for the Lobo and put it in a build box like the one shown or drop it straight into the Lobo but don't know where or who could build it for me. This way I can take out the factory one to keep for a back-up incase anything goes wrong with my build. 

                                                                               Thanks' in advance for all your help and it's nice to be here, I don't feel so lost now.


    Lobo complete.jpg

    Just recently joined here myself and also recently acquired one of these boards. If you're still looking for help I can assemble board. I have a few ideas for bumping it up slightly and posted a somewhat long entry. Haven't seen it up here yet to see if it looks good, if it needs editing? 

    • Like 1
  21. I just recently got one of these Russian boards, which IMO looks like a good piece to work with. I read over the supplied build instructions which are fairly clear, but in a way are not totally, at the same time. I have worked with circuits quite a lot over several years, I went back to a site that discusses working with timer IC's of which in this build uses the 7555, a CMOS version of the vaunted 555 that uses 1/10th the power. This is where the MD transmitter freq. is produced. There are several ways to construct the oscillator and in the case of this design, I find one very small issue. Since as I mentioned, I just got this board and still working at putting it together, obviously I haven't tested it. Here is what I am here to discuss with anyone looking at this version, thinking about building one, or has one working. The 555 system has been know to experience unstable responses if there is no Capacitor connected from pin 5 to ground ! There is no Cap to pin 5 included in this circuit design and it uses a few other features that differ from the basic osc. circuits  A .01ufd cap which on this board can be installed on the back side of the board from pin 5 to the nearest ground buss and should be some improvement to the function and stability of the circuit, it is 'optional' and it will work without it. It is a very small mod but in my experience sometimes that is all it take to work or not. I also suggest to use .100 inch header pins for connecting any of the peripheral parts. Doing this makes it easier to R&R the board for working on it, you will need to be extra diligent about connecting everything back in the proper place but if you have gone this far with this project, that is a no brainer. There are a couple of places the .100 header pins will not fit perfectly but you can get around that with the use of a single break away pin and just a tiny bit of force to re align so your connection will fit as you continue assembly. 3 pins on the right of the rough GB Pot on board are one place, another is the 2 holes just to the right and above the 4 large elect. caps around the Vreg, LM7808 or LM7809, also using a 7809 might give you a slight bit of bump in performance. Since the circuit uses a +12v supply battery, there is still a bit of margin left so that the dropout V is going to remain above the output V of the regulator until batteries are getting too low. Using a battery carrier that holds 8 AA cells, alk or even NiM rechargeables will or should work and you should still be able to get this inside the housing. The use of NiM may exhibit an issue with the 7809 so make the choice based on what battery V you plan on using. One could also use an extra bat pack in series to push the V higher for the input, as the 78xx can handle up to 30v input, this will give you a lot more operation time before the dropout V becomes an issue. I would also think installing some reverse polarity protection here, 'NEVER a bad addition to any circuit and simple, a couple of small diodes and a fuse added to the project, around a 200 milliamp mini fuse is a good rating, put some extras inside the case. The current draw of this unit is very low so you can run your batteries way down this way and still keep going, having a small solar setup would be a good thing to have with you to boost batteries also, you could make it to fit over your hat!!! I am in the U.S. and have considered doing assembly of projects in the future,,, if my board works out. The one good thing I like about this system is that it should work with several different coils out there and one can even construct their own coil if using careful attention. Coils are really not that hard to make if you have and follow the instructions. Making the casing is probably the worst part of it, using resins and hardeners. Shielding is a bit critical here. I will mention that it is almost essential that you have an oscilliscope to build one of these for adjusting the timer section freq. the 5k pot on the left side of the 7555 and also setting amplitude on the upper right of 7555, the one just left of the 14 pin IC spot.. If you don't have a scope, there are apps online that make your PC work as one and you will have to learn how to use it, or get someone that knows to help with it. Also a transistor tester is helpful and when working with these parts, you MUST know the pins and install them RIGHT if you intend to have it work but you already know this if you are thinking about assembling one. 

  • Create New...