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  • missing resistors?

    Hello again -
    ***********
    Oh hey, did you intentionally leave out the 5k1 resistors next to the bipolar caps on LM358 (-) inputs?
    ***********
    Thank you for the scoop on coil construction and hook-up. I see what you mean about the OO coil being unwieldy. That would drive me nuts. Again.

    To people wondering about replacing LF353 with TL072: They are almost exactly identical and work the same.
    TL081 may work, and may be cheaper than LM308, but it consumes about 3X times more power - and it won't work any better. Pay now, or pay later.

    Ivconic, you're right about the LM308 being hard to replace. I'll venture that LM308 pioneered and still sports an -almost- unique combination of features. (PMI) Analog Devices copied it with their *obsolete* OP08. Linear Technology now makes the LT1008. Whuuut else is there?

    I have several of (dual) AD706 in SO08 package that -should- work like two LM308 with "custom compensation" built-in. I'll have to wait and see. I've never used a Golden Sabre, and so I won't know the difference anyway. It should be OK.

    Comment


    • Porkluvr, i do not pay to much attention on batt. test....Whenever it is switched ON it makes a lot of "noise"...Some battery test!?
      Maybe i made mistake there? Right now not able to check sch.
      I am usin almost at all my detectors accu. 12v/1.3Ah...enough supply to let detector stay switched off for hours...days...
      Do not need any batt.test at all. Also do not need noise in some situations.

      Anyway, thats why i disconnected line for test and offered option to "PUSH" button if any test is needed....Also tied ordinary capacitor instead tantalum....same thing....

      Unregistered i am sorry but i do not need to answer on qustions like that....You should have some data charts (free to download) - comparsions charts for op-amps.....No i do not think that you can substitute LF353 with TL071...not at all...
      Yes, you should register.....

      Comment


      • "...12v/1.3Ah...enough supply to let detector stay switched off for ..."

        STAY SWITCHED ON...

        Am i tired or what? Havent sleep for over than 50 hours....Good night!

        Comment


        • 4k7 resistors Disc and GEBl

          Whoops, I'm sorry I meant the 4k7, (not 5k1) resistors (2x) in the signal channels.
          This ommission will reduce signal gain by about one hundred (depending of frequency of interest). Those two resistors are easy to miss because the original diagram is kind of "busy".

          I forgot about the other LM358. I wouldn't bother you about battery test!

          Wait a minute, didn't you get some sleep last week?
          Last edited by porkluvr; 06-25-2007, 10:55 PM. Reason: more specific

          Comment


          • PCB

            Hi, yes i already have the pcb and some components mounted (resistors, caps and some IC bases)
            Don´t know how performance will be afected when i replace some ICs. So this will be confirmed when the project get finish.
            Regards
            Nelson


            Originally posted by Unregistered View Post
            I think that you will be ready before me!I haven't time lately!
            For 308 I understend,but londering can I use TL071 insted of 353?
            I have read that thy are equal and even cheeper replacement!
            But not shore!
            See you...
            Have you made the board allready?

            Comment


            • Finally FINAL !!!


              Hush, sorry i skipped your questions... Well, about nulling;
              Best way is to use oscilloscope while nulling coils.
              But not necessairly. As you said; good will and milivoltemer
              would do the job just fine. Connect TX coil to oscillator.
              Connect RX coil to m.v.metre...Try to achieve as less as possible
              voltage at RX coil as you can get. Do not worry if you cant achieve
              zero voltage. In most cases it will be impossible. It showed to me
              that even up to 0.1 v coil can be useable,depends of device you are
              using with it. Especially Tesoro G.Sabre is very tolerant. Very good
              soluted at geb and disc stages, lets you to compensate eventual loses
              from coil....Thats why i prefer G.Sabre, easy to make coil for it!
              But most important thing comes after...to glue or whatever, coils in
              housing, so good and stiff to eleminate any eventual movements later.
              Also should stuff housing with some lightly mass....I do not want to
              open this subject here, already all explained in Coils forums....
              Nelson, best way to check is to use IC sockets anywhere you want to
              experiment with different ic's. You are in good position to see
              "in vivo" and experience "live" any differences among ic's.
              Just pay attention on pin assignments...Yes, you may try LM1458 instead
              LF353 for example....or TL082... buyt just for comparsions...
              I am not satisfied with LM1458....but TL082 works almost good as LF353?
              Now back to schematic; Yes! Again i made mistake! I omited those 2 resistors!
              Damn! How it is possible? I guess it was in rush...not so good with software
              for schematics...Thanks Porkluvr a lot again!
              OK, now, for the last time, there is absolute correct and accurate schematic!
              Yes, KT315, you are right. Adding parallel 1M resistor improved audio.
              Now it is loud, and no decays while detected item estranged slowly from coil!
              But i got another idea! I added switch, so we can have extra mode!
              Without 1M resistor included in circuitry audio level is directly dependable
              of signal strenght! There is very noticeable decay dependable of relative
              movements of detected item. For example; as you removing slowly coin away
              from coil surface, inch by inch, audio become more weak, decays respecting
              reach/range. With 1m included, audio remains unchanged.
              This can be very usefull on coinshooting! First we detect coin in Decay OFF
              mode (loud and clear). Than switch Decay On and try to locate coin again.
              Audio level can help us to distinguish about size and depth of detected item!
              Very usefull...isnt it!
              Regards!
              Attached Files

              Comment


              • Originally posted by Unregistered View Post
                I think that you will be ready before me!I haven't time lately!
                For 308 I understend,but londering can I use TL071 insted of 353?
                I have read that thy are equal and even cheeper replacement!
                But not shore!
                See you...
                Have you made the board allready?
                Hi guys,
                unregistered and nelson...
                well I think you could use TLC2262 if you can find ! I found them very good and stable, little noise, little consumption , very good dual op amps for metal detectors. They are in bandido circuit as you can see. Use them instead of lf353. You could use also:
                ts272
                ts27m2
                ts27L2
                tlc2252
                tlv2262
                If can't find one of the above use (but take care on consumption) :
                ne5532 (good noise figure but 6ma consumption)
                lm358 (but is noisy)


                NELSON tl071 is a single op amp, you maybe mean tl072. Also tl082 could be
                used but you could have trouble with a bit of noise there.

                For LM308 I suggest (but hard to find):
                NTE398

                or easy to find the LF356/LF357 but consider that you don't need the capacitor at pin 8 anymore. You could leave them in ciurcuit cause LF356's pin 8 is not connected internally.

                Best regards,
                Max

                Comment


                • Originally posted by ivconic View Post

                  Hush, sorry i skipped your questions... Well, about nulling;
                  Best way is to use oscilloscope while nulling coils.
                  But not necessairly. As you said; good will and milivoltemer
                  would do the job just fine. Connect TX coil to oscillator.
                  Connect RX coil to m.v.metre...Try to achieve as less as possible
                  voltage at RX coil as you can get. Do not worry if you cant achieve
                  zero voltage. In most cases it will be impossible. It showed to me
                  that even up to 0.1 v coil can be useable,depends of device you are
                  using with it. Especially Tesoro G.Sabre is very tolerant. Very good
                  soluted at geb and disc stages, lets you to compensate eventual loses
                  from coil....Thats why i prefer G.Sabre, easy to make coil for it!
                  But most important thing comes after...to glue or whatever, coils in
                  housing, so good and stiff to eleminate any eventual movements later.
                  Also should stuff housing with some lightly mass....I do not want to
                  open this subject here, already all explained in Coils forums....
                  Nelson, best way to check is to use IC sockets anywhere you want to
                  experiment with different ic's. You are in good position to see
                  "in vivo" and experience "live" any differences among ic's.
                  Just pay attention on pin assignments...Yes, you may try LM1458 instead
                  LF353 for example....or TL082... buyt just for comparsions...
                  I am not satisfied with LM1458....but TL082 works almost good as LF353?
                  Now back to schematic; Yes! Again i made mistake! I omited those 2 resistors!
                  Damn! How it is possible? I guess it was in rush...not so good with software
                  for schematics...Thanks Porkluvr a lot again!
                  OK, now, for the last time, there is absolute correct and accurate schematic!
                  Yes, KT315, you are right. Adding parallel 1M resistor improved audio.
                  Now it is loud, and no decays while detected item estranged slowly from coil!
                  But i got another idea! I added switch, so we can have extra mode!
                  Without 1M resistor included in circuitry audio level is directly dependable
                  of signal strenght! There is very noticeable decay dependable of relative
                  movements of detected item. For example; as you removing slowly coin away
                  from coil surface, inch by inch, audio become more weak, decays respecting
                  reach/range. With 1m included, audio remains unchanged.
                  This can be very usefull on coinshooting! First we detect coin in Decay OFF
                  mode (loud and clear). Than switch Decay On and try to locate coin again.
                  Audio level can help us to distinguish about size and depth of detected item!
                  Very usefull...isnt it!
                  Regards!
                  Hi ivconic,
                  really nice work. I've tested mc1458 many times also on bandido I've made...with lot of troubles.
                  Now I've realized that these ICs are not so good for metal detectors like these from tesoro. I found that even lm358 is much better than 1458. I've much troubles with low voltage working of these devices: they suffer of erratic working at lower voltages.

                  Audio solution seems a really good idea! And also simple to be done.

                  I've found some good coins with bandido so far...but I'm considering building your GS mod.

                  Best regards,
                  Max

                  Comment


                  • TL082

                    Hi Max and Ivconic, and thanks both of you for replacement information.
                    Unfortunely can´t get that LM308 here. So i ll replace it with TL082 and see what´s going on.
                    Ivconic, th ehole pcb is build considering ICs base on it. I agree, that is a good way to test diferents alternatives on components.
                    Regards
                    Nelson


                    Originally posted by Max View Post
                    Hi guys,
                    unregistered and nelson...
                    well I think you could use TLC2262 if you can find ! I found them very good and stable, little noise, little consumption , very good dual op amps for metal detectors. They are in bandido circuit as you can see. Use them instead of lf353. You could use also:
                    ts272
                    ts27m2
                    ts27L2
                    tlc2252
                    tlv2262
                    If can't find one of the above use (but take care on consumption) :
                    ne5532 (good noise figure but 6ma consumption)
                    lm358 (but is noisy)


                    NELSON tl071 is a single op amp, you maybe mean tl072. Also tl082 could be
                    used but you could have trouble with a bit of noise there.

                    For LM308 I suggest (but hard to find):
                    NTE398

                    or easy to find the LF356/LF357 but consider that you don't need the capacitor at pin 8 anymore. You could leave them in ciurcuit cause LF356's pin 8 is not connected internally.

                    Best regards,
                    Max

                    Comment


                    • AGGHH

                      To whom it concerns:
                      Sponsored by: The number two, (2)

                      It is not recommend that you plug a dual opamp into a single opamp socket. If you have questions about whether or not you can use a particular device as a substitute, it is incumbent upon you to check the device's function and pinout! You can learn a lot from browsing manufacturers data sheets at:

                      ti.com (often more "windy" than necessary"
                      national.com
                      fairchild-ic.com
                      linear.com
                      analog.com (one of my favorites)
                      maxim-ic.com
                      This is just a few, the list is much longer. Aren't sure who to ask? then try:
                      http://www.datasheet.in/ What's that, the Navajos?

                      Datasheets are free to download. If you can read (too much to expect?) and post on this website you can also access datasheets and please quit being rediculous.

                      Comment


                      • Originally posted by nelson View Post
                        Hi Max and Ivconic, and thanks both of you for replacement information.
                        Unfortunely can´t get that LM308 here. So i ll replace it with TL082 and see what´s going on.
                        Ivconic, th ehole pcb is build considering ICs base on it. I agree, that is a good way to test diferents alternatives on components.
                        Regards
                        Nelson
                        Hi Nelson,
                        plvr is right on single op amp...use lf356 or lf357 instead of LM308 and you would be ok. Use tl082 or others to replace lf353 that are dual.

                        Best regards,
                        Max

                        Comment


                        • Hello,

                          Is there some more comon FET that can replace BF245 without change in the preformance of the unit?
                          And MAX why you dont like TL081 for replacement of LM308N?
                          Thanks





                          Comment


                          • hi

                            Can I use 2N3819 insted of BF245C?
                            How do you think?
                            Will this be equal sustitue?
                            Thank




                            Comment


                            • DATASHEETCATALOG.COM BF245-2N4393

                              Comment


                              • to Unregistred!!!

                                Hello,
                                Thanks for your help!
                                Are you share that this will be equal replacement?

                                Comment

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