Worst hobby construction project of all time?

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

formatting link
and
formatting link

More on related topics at

formatting link

--
Many thanks,

Don Lancaster                          voice phone: (928)428-4073
 Click to see the full signature
Reply to
Don Lancaster
Loading thread data ...

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).

Reply to
Richard Henry

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

Reply to
John Larkin

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

Reply to
Warren Weber

large

with

Heathkit

each

buckle.

+++++

thing

showing

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.
Reply to
Richard Henry

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

--

"What is now proved was once only imagin\'d" - William Blake
Reply to
Paul Burridge

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.

Reply to
AZ Nomad

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
 Click to see the full signature
Reply to
Ancient_Hacker

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

Reply to
redbelly

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.

Reply to
Ancient_Hacker

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

Reply to
John Larkin

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
 Click to see the full signature
Reply to
Don Lancaster

Just switch to geranium transistors.

--
Many thanks,

Don Lancaster                          voice phone: (928)428-4073
 Click to see the full signature
Reply to
Don Lancaster

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

Reply to
RST Engineering (jw)

Caver's wrist sundials also do rather well.

For other April suff, see http//

formatting link

--
Many thanks,

Don Lancaster                          voice phone: (928)428-4073
 Click to see the full signature
Reply to
Don Lancaster

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.

Reply to
BFoelsch

[...]

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.....

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
 Click to see the full signature
Reply to
Adrian Tuddenham

Howdy!

Oh, I dunno. Pick the oscillating opamp up, hold it in the air, and then release the hold.

It'll detect the gravity waves just fine, thank you B)

RwP

Reply to
Ralph Wade Phillips

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

--

"What is now proved was once only imagin\'d" - William Blake
Reply to
Paul Burridge

It draws less quiescent current that way. ;-)

--

"What is now proved was once only imagin\'d" - William Blake
Reply to
Paul Burridge

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.