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    • #8414
      rj4u
      Participant

      Does anyone know of a source for 8072 earphone. Magnetic(not ceramic) 300 ohms. Seems as if everything available in the old style ear pieces is no ceramic.

      • This topic was modified 4 months, 1 week ago by mwpeters75.
      • This topic was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #8417
      mwpeters75
      Keymaster

      Welcome RJ4U to the forum.

      I will defer to Guenther who is our resident Lectron System legacy parts knowledge expert.

      I certainly have an earphone block that I can give you, I just don’t know if it is magnetic or ceramic.

      Best regards,
      Michael

      • This reply was modified 4 months, 1 week ago by mwpeters75.
    • #8419
      Guenni75
      Moderator

      All Lectron earphones are – magnetic – 300 Ω versions -because they may be used as an alternative to the speaker block (with output transformer). The coil(s) are like the output working resistors for the transistor amplifier, and there is a current of some mA. Therefore no 8 Ω version must be used – the transistor will get hot and “die”!

      The crystal version (sometimes called ceramic /piezo) is like a condenser / capacitor – there cannot flow any current, so this won’t work for a “normal” Lectron amplifier stage. No ohm value can be measured checking this kind of earphone, and they were bigger (used in the 1950ies and meanwhile very rare), see details in this photo:

      Hope that helps.

      G.

      • This reply was modified 4 months, 1 week ago by Guenni75.
      • This reply was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #8421
      rj4u
      Participant

      Hello Guenther,

      Thank you for your response, I see I had a typing error in may question. I was wondering if any of you folks know of a resource for the old magnetic style earpiece. I do understand how the earphone is used in the amplifier stage as  DC coupling, clever use of the components available. I need a replacement for my Lectron system. I have spent a number of hours searching for a 300 ohm magnetic replacement with no luck. I have found that there are times when things like this may be available on the European market and less available in the US such as the 6 V 50 ma. E10 lamp. I have more details about my efforts that I will share later. I have just recently discovered this portal into the world of Lectron and I look forward to exploring.

      Thanks

      Bob

      • This reply was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #8422
      Guenni75
      Moderator

      Hello Bob,

      sorry – no source known at this time for 300 Ω earphones – in the 1960/70ies these could be purchased in Europe. But the fellow Lectroneers may have one or more pieces in their spare parts – it’s always good to have doublettes…

      Perhaps Michael can help – otherwise I may send you one or two.

      Best regards,

      Guenther

      • This reply was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
      • This reply was modified 4 months, 1 week ago by mwpeters75.
      • #8428
        mwpeters75
        Keymaster

        Hi Bob and Günther,

        First, thanks very much for this great history!  I am always learning something new from you Günther 🙂 

        Out of curiosity,  what are the current Lectron-RWO earphone blocks using in terms of impedance and build materials?

        Bob, I would be very pleased to send you an earphone block for your model 3 rebuild.  Just send me your mailing address by email and I will take care of this at no cost to you.  Do you have the first version or the expanded version of the Raytheon Model 3?

        Welcome again Bob, we are all pleased that you are onboard and look forward to your future contributions.   May we understand how you came to find the Lectron.Info portal? 

        Best regards to all my fellow Lectroneers,
        Michael 

    • #8429
      rj4u
      Participant

      Hi Michael,

      Probably too much information but here we go. I am an RF engineer, a luthier, and an avid woodworker. In 1969 I received a Lectron Series 3 set for Christmas. My father was an engineer so I suspect he had an interest in it also. I have no idea what happened to that set but I have always remembered it clearly in my mind. I could remember the blocks and the different circuits I could build but for the life of me, I could not recall what the set was called or who made it. Finally, over the past year I was able to identify what it was by finding one on Ebay. After I identified Lectron, your site was an easy find.

      Now being  one who builds things I though with this website I have enough information that I can recreate this Lectron kit and I have. The attached pictures show the complete series 3 kit. All components are contained in the blocks. NTE equivalent transistors. I still have to finish the speaker block and I need to obtain a 300 ohm magnetic earphone. I have built all the circuits except the radio circuits and they work. I need to finish the speaker block and I may build an inductor block to replace the earpiece so that I can build the three transistor radio. I will have a large smile on my face when that one works.

      Once working, this reproduction Lectron Series 3 will be shared with the young engineers at work. Give them a lesson on what a transistor is and what cool toys we had in the 60’s and 70’s. After that, it may end up in the library where my daughter works as a librarian. She runs the STEM programs and this would be fun for the kids to play with. Maybe even spark some interest.


      So there you have it, I look forward to collaborating with the Lectioneers on this site. So far the response has been great.

      Regards,

      Bob

      • This reply was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
      • #8431
        mwpeters75
        Keymaster

        Hi Bob,

        Wow, this is something new, reproducing an entire Lectron model from scratch.  Congratulations!  I like the ‘JohnsLectron’ moniker on the speaker block 🙂

        Thank you for your background information.  It is always very interesting to know how and when a person was introduced to the Lectron System and what influence it might of had on them growing up and in their business career.  A luthier is indeed a great tradition of craftsmanship.  I am a flute and penny whistle player in my troupe called The Trouvères.

        All the manuals may be found on the documentation page for each reseller.  If you need any help finding things please let me know.  Thank you for introducing the Lectron System to your young engineer colleagues.  I hope that they will also join us here at Lectron.Info.  Photos and videos of you and your colleagues using the Lectron System would also be welcome to add to the human interest story.

        As you explore Lectron.Info, you will find numerous videos and photos created by Günther  and Frank.  Well worth a look!

        Best regards,
        Michael

        • This reply was modified 4 months, 1 week ago by mwpeters75.
        • This reply was modified 4 months, 1 week ago by mwpeters75.
        • This reply was modified 4 months, 1 week ago by mwpeters75.
    • #8435
      LectronFan
      Moderator

      Hello all,

      Wow, this has never be done before I guess, a Lectron replica !

      I like the way the symbols are crafted on the wooden surface.

      Did you use magnets underneath ?

      How do your cubes make contact ?

      The original Lectron cubes have silver contacts with magnets, so they attract each other and make perfect contact.

      The earphone included with the new sets looks like this :

      I measured it’s resistance and it measures about 278 Ohms. So, It’s inductance should be a bit higher then this.

      As Guenther mentioned, it cannot be replaced by an 8 Ohm earphone.
      The light bulbs 6V, 50mA are easy to get here in Europe. Maybe Ebay can be your resource.

      Concerning the speaker, be aware that it is connected to an output transformer. Speaker and transformer reside in the same cube.

      The original  Ge transistors, diodes, light bulb, speaker and transformer are easy for me to buy here, if you would need these, let me know. I’d love to help you.

      It’s cool to introduce this to your colleagues, I did the same and they were astonished !

      Maybe you can build a set for your own and try the experiments out proposed here on the forum.

      many greetings,

      Frank

      • This reply was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #8439
      rj4u
      Participant

      All,

      Thank you all for your kind words. This build is almost complete with the exception of the earphone. I have been offered an original Lectron earphone which I very much appreciate. I would take you up on this offer but I feel it is not right to use an original Lectron block for this reproduction. They are scarce and should remain as original. However buying a new one as shown in Frank’s message seems reasonable. How do I get new individual blocks? Is this possible, or must it be a set?

      All the circuits in the Raytheon Manual except ones requiring the earphone are working. I will share more as I finish up with this project build.

      Thanks,

      Bob

      • This reply was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #8443
      LectronFan
      Moderator

      Hello Bob,

      Thank you for the info and pictures, this shows off your art of work !

      A  new earphone is still available and can be purchased here

      I don’t know if they would send it outside Europe, if not I can always do it for you. Maybe Guenther (who lives in Germany) has one for you.

      Many greetings

      • This reply was modified 4 months, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #8438
      rj4u
      Participant

      Hi Frank,

      Some details on the cubes:

      There are two magnets on each face with N-S on each face clockwise around block. This allows the blocks to connect any face to any face. Ring lungs are in front of each magnet and provide for the electrical interface, physical contact between blocks, solder lug internal to block. Magnet on bottom provides attachment to ground plane and again ring lung on bottom terminal where required.

      Speaker block has 8 ohm speaker and 600 ohm center tapped to 8 ohm transformer. Center tap gives me 300:8 transformer.

      NTE equivalent germanium PNP transistors.

      Markings done with laser cutter.

      Regards,

      Bob

    • #8482
      mwpeters75
      Keymaster

      Günther wrote to me in an email with a lot more detailed information about how the earphone works and provides an interesting discussion about impedance.

      The (classical) sound converter is the electro-dynamic version. It consists of a membrane made of thick paper or thin plastic (waterproof) which has a cylindric coil (some dozen … some hundred turns of thin isolated copper wire.

      This coil is movable in a cylindric hole in the magnet, so that every AC voltage acts to move the coil (with the membrane) up and downwards (like a pump or a special motor) – this “generates” the noise / music etc..

      A cross-section drawing is appended as #1.

      This principle is used in all the classic microphones since ~ 1950 (not elektro-stats! That’s a complete other world, see later), loudspeakers of any construction and size (not high-tone piezo-tweeters!),  classic headphones (not special High-End constructions, see later) and EARPHONES (not piezo/crystal/quartz versions!)

      => ALL LECTRON earphones are ALWAYS electro-dynamic 300 ohms! Why?

      Because they can be used instead of the loudspeaker block (you may measure: ~ 300 ohms, like the earphone!) Therefore all the year until today this are the two types in my photo to the right. The one version (newer) in white with metal plate, and the other (Miss) Piggy-colored for many years and today (with the two plugs) as part of the Buchlabor. The “universal component tester” can show you all values of this blocks / parts – so please use it…

      And look at the electric symbol of the earphone block: what do you see? A thick black line (= membrane) on a square (= magnet with coil) – what does it mean?

      YES – an electro-dynamic phone – similar to the loudspeaker symbol where the trapezoid means the funnel shaped membrane, see #3 + 4.

      Therefore you cannot use the mass of cheapest earphones / earpieces with 6 / 16 / 32 ohms – the amplifier transistor will smash! These earphones were given with all the millions of pocket radios since 1955. Meanwhile these earphones (sometimes two for stereo) come in huge container ships from China and are not worth the money…

      and cannot be used with Lectron, too.

      Only some of my special circuits and applications may be used with these…

      Forget the word “ceramic”! What does is mean common? I don’t know – perhaps a ceramic housing? Ceramic has no physical and not any electric properties!  I cannot make music with a ceramic tile! I may glue it on the bottom or on a wall in my house – but does it make music???

      What could be meant is: a ceramic wafer with gold leaf membranes like in this version of a limited edition (300 units) of the best headphone of the world, together with this special amplifier (!) and an output of 400 V (!) to drive the headphones – called ORPHEUS HEV90 – for 30’000 DEM (1991) see appended advertisement of SENNHEISER Germany #2.

      Last but not least: all crystal / quartz / piezo (= tiny metal plated ceramic strip, since ~1953 used as “saphire” pick-up in record players) have a no ohm value – because “stone” is not an electric conductor (!) sometimes it is so simple…  Perhaps more than 100’000 kohms but: forget it! Sensitivity: quite good, quality: bad – not / never for Lectron!

      By the way: the symbol(s) of piezo/… whatever material phones / pick-ups / tweeters is a rectangle with a plate on each of the both long sides (like a capacitor  filled with a small brick and glued with a foil working as membrane…) – so simple can it bee in our life – see #5.

      And now some words to “impedance”: depending on the construction, kind of metal / coil and weight of the metal components the coil may have different resistor values in the range of 35 … 20’000 Hertz/cps . Always at 1 kHz/kcps (= 1’000 Hz/cps) an impedance will be measured and offered in catalogs etc. as “Z = xxx ohms”, where “Z” is the impedance unit and ohms are the measured value at 1 kHz. This can be done only with expensive measurement tools in specialized  companies, drawn as a “curve over f”, f = frequency.  (low frequency = lower resistor value, high frequency = higher resistor value).

      So the “real resistor value” may be 255 or 310 ohms, but the “impedance value” can be 350 / 500 or even 1000 ohms – never care! Everybody in the “background” knows it – and that is enough…Not to confuse all people 😉

      Hope that helps,

      Guenther

      • This reply was modified 4 months, 1 week ago by mwpeters75.
    • #8484
      LectronFan
      Moderator

      That’s it !

      The best explanation ever !

      One thing to mention in favour of the crystal earpiece, it has such an incredible high impedance that it has been and still is used for crystal radios.

      It poses no load on the circuit and is very sensitive for very weak signals.

      In our Lectron environment, we can perform many cool experiments with the 300 Ohm earpieces, not yet mentioned in the manual.

      But that’s a different topic, I will come back to this later.

      Greetings

    • #8485
      Guenni75
      Moderator

      Frank,

      you are right – the use of crystal radios with the sensitive piezo earpieces is important to notice. There were many funny constructions and “designs” for this kind of children’s tiny radio like this one:

      The content: a reception coil built as a variometer, one capacitor and one diode for detection. With a little more money you got a variable capacitor with a fixed coil for tuning (similar to the well-known Lectron tuning block). Reception of AM BC stations only with a cable to connect with the metalpart of a water pipe (as GROUND / EARTH, ~ antenna) or heating, and – of course – with the piezo earpiece.

      As an alternative to this piezo model you could use the good old headphone set (since ~ 1920) with one or two capsules, each 2000 Ω impedance. This type is a magnetic version, with coils on a permanent magnet iron, which moves a thin metallic membrane:

      A couple of years an exponential horn could be placed on a capsule to listen without this quite heavy metal headset:

      Much later a high-impedance Hi-Fi headset like the famous HD-414 (Sennheiser, ~ 1969) with 1800 Ω each channel (isn’t she lovely?) could be used with good sound quality:

      or the follow-up model HD-424:

      The sound with these models (open systems = you could hear what’s around you, e.g. telephone or housedoor bells) are really splendid, beleave me!

      Best,

      G.

      • This reply was modified 4 months, 1 week ago by Guenni75.
      • This reply was modified 4 months ago by Guenni75.
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