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Basic transistor BFO detector

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  • Basic transistor BFO detector

    Hi Can anyone me help find some information on a bfo self build components only kit, that I bought in the UK mid 1970s, as I have lost all the paper work and information.
    The reason I am asking is it's a bit disconnected and would like to get It going again,please let me know if you need any other info.
    Many Thanks Arthur.

  • #2
    Phew!!! Not a lot to go on,.... any name/info on the circuit board????? Any chance of a photo of the board/components??? How many knobs/dials? and any labeling/marking on them??

    Cheers, Fred

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    • #3
      Basic bfo detector

      Hi Fred
      I have been away from home for personal reasons, and can do all you ask when I return today.
      The kit came with circuit board and components, including a 4 way push button switch, and a little meter, and instruction pamphlet.
      There is an I c chip in the circuit,and some writing on the circuit board I will forward all this Info
      when I return home today.
      Many Thanks Arthur.
      PS I am very new to using Forums, Can you send pictures
      on this site and HOW!!

      Comment


      • #4
        Originally posted by pipdip View Post
        Hi Fred
        I have been away from home for personal reasons, and can do all you ask when I return today.
        The kit came with circuit board and components, including a 4 way push button switch, and a little meter, and instruction pamphlet.
        There is an I c chip in the circuit,and some writing on the circuit board I will forward all this Info
        when I return home today.
        Many Thanks Arthur.
        PS I am very new to using Forums, Can you send pictures
        on this site and HOW!!
        When you post a reply, scroll down the page and click on "Manage Attachments". Note the allowed file types and maximum file sizes.

        Comment


        • #5
          basic bfo detector

          Hi fred
          On the circuit board is written ( The Bionic Ferret ) also the word ( Ambit ) the IC is ( LM 3900 M ) ( ZTX 107 ) (4 ) ( MBF 256 B ) ( 1 ) ( MVAM 115 ) ( 2 ) There is also a small meter with needle, and a 100k long plastic pot.
          I have taken the circuit out of it's housing to take the picture.
          I hope all this helps Fred. Arthur
          Attached Files

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          • #6
            We have a number of good BFO circuits that work as well I would think.

            Comment


            • #7
              ambit

              ambit projects rarely worked. thats why they went bust. google " how to make a metal detector " several projects. no need to spend a fortune

              Comment


              • #8
                My bfo detector

                Fred,do you think it's possible I can get hold of my actual circuit diagram, and any relevant paper work. Thanks Arthur

                Comment


                • #9
                  Reference to AMBIT radiometer but not your circuit ...

                  http://www.thunting.com/cgi-bin/thun...diometer.shtml

                  Comment


                  • #10
                    Originally posted by pipdip View Post
                    Fred,do you think it's possible I can get hold of my actual circuit diagram, and any relevant paper work. Thanks Arthur
                    You may be able to repair it without a circuit diagram. By the look of it, it's in a terrible condition, there are water drops on pcb. Most likely the contacts on the switches are oxidated - you should replace the whole switch module. I would also replace the multiturn pot and the other three semiadjustable pots, clean the board very well with isopropyl alcohol on both sides, replace all the electrolytical capacitors, measure with an ohmmeter in circuit all the resistors (probably they are ok). Dry the board with a hair dryer after you clean it. Also check the coils and the inductors on PCB for continuity.
                    A better idea is to build another detector based on the projects available on this site.

                    Regards,
                    Nicolae

                    Comment


                    • #11
                      BFO that works

                      Its easy to waist a lot of time on this. We are all fascinated to see the circuit diagram. Just can’t help it. From what I can remember. There were some clever people at Ambit. Designed Amstrads 1st computer I think ,but a lot of their projects never worked and contained a lot of unnecessary fm radio bits. like the meter, coils and push buttons. Your kit probably cost about £30 in 1980 equivalent to about £300 now. The most expensive BFO I had was a Garrett £150 in about 1980 This never worked any better than another BFO Qtone that cost less than £20 that I had . You can get the plans to build this at www.easytreasure.co.uk/bfo.htm The secret in a good BFO is in the tuner. Ambit started selling electronic components and kits from a small shop in Brentwood High street above a wet fish shop. Then moved to a massive building just up the road. Then went bust, leaving many with half built expensive CB radios.

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                      • #12
                        Just love that PCB photo. Look about 15mm to the right of the LM3900, see the wire link over the resistor. I guess the electrons don't care, but....

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                        • #13
                          Originally posted by Skippy View Post
                          Just love that PCB photo. Look about 15mm to the right of the LM3900, see the wire link over the resistor. I guess the electrons don't care, but....
                          It also looks like it's been repaired (or maybe modded) in several places as well. There are caps and resistors which have had their leads cut and then been resoldered. Also, look at the transistors at the bottom left of the board. Both of them have a pinout that doesn't match the silkscreen.

                          Comment


                          • #14
                            Originally posted by moodz View Post
                            Reference to AMBIT radiometer but not your circuit ...

                            http://www.thunting.com/cgi-bin/thun...diometer.shtml

                            Anybody ever try and build that project ?

                            Comment


                            • #15
                              Originally posted by 6666 View Post
                              Anybody ever try and build that project ?
                              Yes, I never could get it to work .

                              Comment

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