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Worst hobby construction project of all time?

Discussion in 'Electronic Design' started by Paul Burridge, Jan 8, 2006.

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  1. My nomination would be the Sinclair Micromatic radio, circa 1970. Cost
    when new 22/6d.
     
  2. Someone just asked me what the worst hobby construction
    projects of all time were. In general, Ziff Davis quality
    control was ridiculously better than Gernsback, so much of
    the really bad stuff appeared in Radio-Electronics and its
    renamed and repositioned offspring.

    I'd guess that a RE cable tv descrambler project caused the
    most grief. Fatal errors in the story were combined with the
    highly restricted places where it would work, added to the
    questionable skills of the theft-of-cable epsilon minuses.

    But my vote for the most mesmerizingly awful hobby project
    of all time would have to be the magic lamp in the April 96 RE.
    This was a "free energy" project that was so "not even wrong"
    on so many levels it clearly was one of a kind.

    The premise was that if you took a half wave dimmer circuit and
    used a 32 volt incandescent bulb lit to normal brightness, your
    cheap average responding meter would record only one-third
    the voltage and one-third the current. For an obvious power
    savings of 90 percent. In reality, of course, we had standard
    beginning EE student blunder #0001-A of confusing average
    and RMS current and voltage readings.

    Naturally, the author never bothered to touch the 32 volt bulb
    to see if it was any cooler. Compounding ludicrosities included
    a patent being granted on a mainstay circuit found in most any
    1938 industrial electronics textbook, the circuit being illegal
    because of power quality considerations, and extreme stability
    and bulb lifetime issues over late angle phase. Compounded
    by the author's belief that a conspiracy was doing him in.

    Amazingly, at a 126 degree half wave dimmer phase delay angle,
    the ratio of average to RMS current is in fact a whopping 3:1! I
    did a detailed analysis of related topics in
    http://www.tinaja.com/glib/MUSE112.PDF and
    http://www.tinaja.com/glib/MUSE113.PDF

    More on related topics at http://www.tinaja.com/whtnu06.asp

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  3. My personal worst was a Heathkit desktop calculator kit. One of the large
    plastic electrolytic capacitors was marked backward, but still fit nicely
    into the circuit board with no hint of the problem. When powered up for the
    first time, there was nothing, so I was probing around with my Heathkit VTVM
    when the plastic case of the cap finally let go. The largest piece of it
    whacked me in the forehead, leaving a nasty cut.

    There was enough of the other end of the cap still solderd to the board to
    show the mismarking, so the LA Heathkit shop rebuilt the whole thing under
    warranty.

    Thinking about it, there was also the Heathkit quadrophonic synthesizer that
    just _seemed_ to do nothing (but that one didn't jump up and bite me).
     
  4. Warren Weber

    Warren Weber Guest

    Two ideas in one of the issues did not work too good. A solar powered flash
    light and a one station intercom. (<:) April issue.
     
  5. John  Larkin

    John Larkin Guest

    Nuts&Volts did a gravity wave detector. It was an opamp with negative
    feedback and an electrolytic cap between the inputs. It made a
    randomish low-frequency output; maybe it was oscillating or something.
    A lot of interesting physics accompanied the article.

    John
     
  6. AZ Nomad

    AZ Nomad Guest

    My problem with their scientific calculator was the gas discharge displays with
    30 pins or so that had to fit in to the crappiest "socket" possible. Heathkit
    didn't actually supply a real socket, but had individual recepticals for each
    pin that fit poorly and tended to cause the wire from the readouts to buckle.

    I don't know how the hell you could get a electrolytic wrong. They had +++++
    and ----- in big letters along the body and heathkit always made a big thing
    about the importance of connecting them correctly including big pictures showing
    you what went where.
     
  7. It was one of those big black plastic electrolytics with ++++ on one side
    and ---- on the other. If you looked closely, the leads, which both came
    out of one end of the cap, were slightly asymmetrical. However, the part
    still fit within the silk-screened circle on the PWB. After it blew up,
    therre was enough of the cap body left, complete with the remnants of the
    ++++ and ---- markings, that I could see that the asymmetry was incorrect
    from the other caps that were marked correctly. The Heathkit shop guys
    agreed; that's why I got the warranty repair.
     
  8. [...]

    I'd wote for the parking lamp controller in Practical Wireless around
    1967.

    It was in the days when parked cars on a public road had to show a light
    at night, so this gadget was intended to switch a 12v bulb on at dusk
    and off at dawn, to conserve the car battery life - unfortunately it
    didn't quite do that.

    The 'designer' (and I can still remember his name) had put negative
    feedback instead of positive feedback around the current amplifier.
    Instead of snapping smartly on and off, the bulb hovered at various
    levels of glimmer throught the night and the day; and the 'switching'
    transistor needed a substantial heat sink.

    He also did a stereo decoder which was a direct crib of a Mullard
    circuit with the component values changed. It is a pity he 'improved'
    it by putting DC blocking capacitors between the base dividers and the
    bases of the transistors.....
     
  9. Hehe! Detecting gravity waves takes a bit more than an oscillating
    opamp, as you're no doubt well aware. :-D
     
  10. It draws less quiescent current that way. ;-)
     
  11. Worst ever-- ( I hope Don Lancaster didnt design this one!) -- the SWTP
    FET preamp. Assembled just fine, and it *worked* as a preamp. And as
    an AM radio. And as a FM radio. And as a TV. All at the same time.
    At about the 20-watt level. Must have been engineered in a submarine.

    The balsa-wood cover didnt provide much shielding either. I learned a
    lot about shielding and the efficacy of resistors right at the base or
    gate as a simple low-pass filter. Eventually got it tamed so you had
    to turn up the volume all the way to hear the news.

    ----
    Kinda shaky: The SWTP TV typewriter power supply. They supplied the
    cheapest diodes imaginable-- the diode body was some very soft spongy
    white plastic which got even softer once under power. Had to replace
    those mighty quick with some 3-amp diodes. . The filter cap had high
    ESR and couldnt provide enough juice throughout the whole cycle.
    Fortunately the LM320 came out right about then and made a much better
    regulator.

    The TV typewriter itself was pretty darn good-- especially after you
    added the very necessary scroll and auto-line clear widgets. And the
    lower-case addons. And the 64-character wide screen mod. Then it made
    a nice computer terminal.
     
  12. redbelly

    redbelly Guest

    Reminds me somewhat of some power supply connectors I've gotten from
    Rad Shack in recent years. Two pins protrude out of a circular plug.
    Along the side of the plug, exactly HALFWAY between the two leads, a
    "+" is clearly marked.

    Mark
     
  13. One pretty bad one was an electronic calculator, using neon ring
    counters and a old phone dial to enter the digits. If you've ever
    looked at a neon ring counter, it's one of those circuits that just
    BARELY works for 5 minutes at a time, assuming nothing changes more
    than 2%. And that includes supply voltage, incident light, body
    position, charge, and cosmic rays.

    To get it to work at all you had to buy a big batch of neons, then
    "age" them at medium current for a few days, then manually measure the
    breakdown voltage of each one, and sort them into batches of ten with
    very close breakdown voltages. You had to be careful not to drop a
    bulb-- that can bend the electrodes and change the breakdown voltage by
    several volts. Then you had to wire up FIFTY parts for each decade. A
    real tedious nightmare.
     
  14. Ah yes. They work blooming wonders! ;-)
     

  15. An electrolytic is a witches brew of bizarre chemistry.

    Logical explanations were plain old temperature sensitivity, but any of
    a number of electrochemical processes could easily be doing as they damn
    well please.

    Gravity waves were about the LAST of the probable explanations.

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  16. Just switch to geranium transistors.


    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  17. John  Larkin

    John Larkin Guest

    The jerk who does the circuits column for N&V (I've supressed his
    name... I know the editor hates him) likes to put diodes in series
    with capacitors.

    John
     
  18. Oh, I like that. I'm always looking to find something for the April issue.
    A one station aircraft intercom is a magnificent idea. I'll plagiarize that
    directly, thank you {;-)


    Jim


    Two ideas in one of the issues did not work too good. A solar powered flash
     
  19. Caver's wrist sundials also do rather well.

    For other April suff, see http//www.tinaja.com/glib/marcia.pdf


    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  20. BFoelsch

    BFoelsch Guest

    There was a circuit not too long ago of an experimenters power supply that
    provided + 0-20, - 0-20 and regulated 5V. Sounds good, except that these
    voltages all came from a single 24V transformer. The secondary of the
    transformer supplied 3 full wave diode bridges. The + bridges had their -
    sides grounded, the - bridge had its + side grounded. Of course, this
    shorted the transformer secondary through the bridge diodes and the common
    ground.
     
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