An Electronic Notebook » The Universe of the Lectron System

This topic has 2 replies, 2 voices, and was last updated 4 years, 1 month ago by Guenther.

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- 2020-February-26 at 04:29 #8330
 Guenther
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 Since 1967 so-called electronic notebooks (voice recorder) based on magnetic tape (cassette) were used in the offices or whereever nobody was writing down spoken words immediately.
 One of these early models (Grundig EN7) used an integrated circuit with 3 transistors and 2 resistors (hey!) in a TO-72 outline and 4 pins: TAA141 (Siemens) or TAA263 (Valvo).
 The schematic of the EN7 – as one example of this very simple electronic:
 
 Some time ago I found this IC in my huge mass of old spare parts – and I tried to re-build this voice recorder…
 The problem was: I had no cassette mechanical parts, all trashed over the years. But the universal online auction house had some alternatives: a quite strong used portable cassette player for 3 V with function for Euro 1.00.
 I removed all unnecessary parts (except the motor etc.), and built a connection block for the record/playback head. The microphone can be the Lectron earphone #8072 (with ~ 200 Ω impedance!) or a loudspeaker / transformer combination (even the Lectron loudspeaker #8038) or (here): a 50 Ω with a tapped transformer coil:
 
 Version with Earphone:
 
 The function is given, the loudness (playback) low – because the original version had to held against the ear! And for recording a louder speech will be better for a good quality. Please note: in that times those (mini-) cassettes were erased with a big magnet (!) and not with an erase head.
 You may say: so what!
 This is one way to explain nowadays the function of storing voice & music on a magnetic tape. The young people from today never used (or knew about) this techniques as I was told. This was used since 1935, first – and for a long time – on big tape recording machines with speeds up to 76 cm/sec, since ~ 1972 with standard music cassettes in portables (4.75 cm/sec).
 Mr. Birett built a tape head block to demonstrate this storing technique in his physics lessions. He pulled a piece of tape at the head in both directions using Lectron amplifiers to get the “strange” sound, because the speed of the tape is very important for a good understanding / recognition.
 Another nice application is to use such a simple cassette player – and leading the 4 stereo head lines plus GROUND to one or more connection blocks – as a Mono / Stereo forward and BACKWARD player – or a mix of one forward + one backward track (or only one or both backward tracks) for an exiting “Guessing Game”: guessing singer / title / group. Or learning to speak backwards – that’s a real and serious hobby! This can be done with the “normal” Lectron blocks with transistors – or the 2-stage amplifier – and the loudspeaker.
 Another way is to use Frank’s Difference Amplifier and / or Tone Control to create new sounds.
 Best regards,
 G.
 - This topic was modified 4 years, 2 months ago by Guenther.
 - This topic was modified 4 years, 1 month ago by Michael. Reason: Changed font and size styling for easier reading
 - This topic was modified 4 years, 1 month ago by Guenther.
- 2020-February-27 at 01:15 #8338
 LectronFan
 Moderator
 Hello Guenther ,
 
 Hmmm, this seems like a nice circuit to play and tweak with.
 
 A very long time ago, I also used to experiment with tape speeds and reversing playback.
 
 You made a very good looking block for this. How do you get the drawings on the white cover ?
 
 Greetings
 - This reply was modified 4 years, 1 month ago by Michael. Reason: Changed font and size styling for easier reading
- 2020-February-28 at 07:54 #8401
 Guenther
 Participant
 Hi Frank,
 
 the cover drawings are done with the free IRFANVIEW program. First I make a copy from a suitable Lectron Info Card or a template. Unnecessary symbols / description etc. can be deleted and new symbols like circles, squares, triangels, and rectangles can be placed via the EDIT menu function “show paint dialog”. The connections with lines (best: 4 pixel) and the values and / or connection names / numbers with the text “A” feature. The soldering points are done with the “brush” symbol (12…15 pixel). Here a template for 27 x 81 mm:
 
 Important seems to be the reduction to 16 colors and save – after a couple of actions are successfully done – to a PNG format. I had the bad effect that sometimes the program suddenly stops… may be that my downloaded version had some bugs. If I have copied symbols, graphics or the like into the image I have immediately to go back to 16 colors (!) and set the contrast (no light gray in my drawing) higher + SAVE.
 
 Meanwhile I can rotate the new “card” to get the right direction of text if no sufficient space is in the horizontal position.
 
 This is only a sample to show some actions I had done outside the “cover”:
 
 After having completed the card it may look like this:
 
 …here I integrated at least a photo to show the possible / required connection blocks for a complete function.
 
 The next step is to cut out the cover drawing and paste it into an empty PNG file (menu: create new – empty – image) and print this cover with the wanted size, e.g. 28.5 x 82.5 mm (including the thin frame).
 
 I collect several new “covers” to a total printout in A6 size printed with my old HP deskjet 882C and copy these all with my even older Canon Laser Copier on A6 photo paper 230g.
 
 To make these new covers resistable to water, fat and other bad influences I laminate it with adhesive transparent foil (used for book covers etc.) – the best but rare to get is foil with a matt surface. It will look like an original cover… After all I glue the cutout onto the block cover and about 10 minutes later I can cut the black frame off – ready!
 
 Hope that helps,
 
 G.
 - This reply was modified 4 years, 1 month ago by Guenther.
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