Worst hobby construction project of all time?

My nomination would be the Sinclair Micromatic radio, circa 1970. Cost
when new 22/6d.

 

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

 

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).

 

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

 

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

 

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.

 

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.

 

[...]

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.....

 

Hehe! Detecting gravity waves takes a bit more than an oscillating
opamp, as you're no doubt well aware. :-D

 

It draws less quiescent current that way. ;-)

 

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.

 

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

 

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.

 

Ah yes. They work blooming wonders! ;-)

 

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

 

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

 

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

 

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

 

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

 

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.