Narrow-Bandwidth Television Association

Many a published item has flaws in it, here's an example from a 1969 'Wireless World' article. Can you spot the error?

78/79xx regulators weren't available in those days, so that's not it...and it's not really an error anyway, this arrangement doesn't regulate at all, but allows you to set a 'nominal' voltage...

There quite a few other gaffs in the same item (though not this circuit) as well as poorly thought out circuits, but I guess one cannot expect Editors to do an analysis on every circuit they receive.

No prizes...except being the first to spot it...

Steve A.

OK, here's another one, also PSU-related from Electronics Australia in 1974...a well respected monthly in its time....care to mention what's wrong here?...a clue, it's in the low-volts section, the hi-volts appears to be OK...

Steve A.

Oh, rectification is always so difficult. Those Graetz bridges and then with voltage doubling. How to place the diodes and interconnect them and where to place the capacitors and in which polarity.

No, then software is so much easier. And with no risk to burn your hand on the wrong end (which one was it?) of the soldering iron.....

OK, no-one seems to have said they've spotted the errors, but I suspect a few have including Klaas.

The first power supply puts a two-diode short across the secondary of the transformer. The action of this is shown below with the help of arrows added. (Conventional current flow). Both phases of the transformer output are shown.

In the second one there's a voltage-doubling capacitor in the wrong place. As drawn it will be charged with reverse polarity.

Steve A.

Spot the error....doesn't seem to be bothering john ?

Yes Steve, that is exactly what I spotted. But I didn't like to spoil the puzzel for others, so I gave an "encripted solution". But still it is difficult if you like to get more DC output voltages from a transformer that look to have too low voltage at its secundary windings. I always have to think it over very carefully before bake it together.

Thanks Klaas for not spoiling it for others.

Two well respected publications in their day can make slip-ups like this. No doubt an 'Errata' was published in later editions. It seems like WW were going through a difficult time. At the end of this item is the Errata for previous issues, it's quite long and covers quite a few circuit mistakes and text errors...maybe they were short of knowledgeable staff at the time.

When you think that something 'looks wrong' try and analyze it as best you can, just because it may come from an esteemed publication doesn't mean it's correct. This applies a thousand-fold over on the Internet where there's no Editor or peer review.

Steve A.

..no Editor or peer review.

That'll be the systems that produce petrol(gas) from water or perpetual motion machines.

Graham

Graham, agreed, a concept that usually works, but is evident here that it has flaws, as well as instigating a bureaucratic process for those that don't wish it.

Can you imagine if all circuit diagrams here on this forum had to be vetted? ..as well as the accompanying text? Pictures? Videos? No thanks. And who would do the vetting? I'm not putting my hand up for the job.

If I spot an error I will politely point out my concerns, but I also could be very. very wrong. I've made some right gaffs in my time, but I'm not going to draw anyones attention to them.

Steve A.

Perpetual motion...it's called Creative Accounting these days...

None-the-less I think one of the advantages of posting projects/circuits/software to the forum (and Newsletter) is the opportunity for peer review. Anything of any complexity at all can always benefit from that.

One should be thick skinned when having errors corrected, it can happen to anyone, after I once made a mistake myself, yep, I remember distinctly once thinking I had made an error - and I was wrong!

Seriously, some of the software I have posted here is reasonably complex and without the help of people here, and elsewhere, testing it, using it, commenting on it, etc, it would be a lot buggier! So keep the feedback coming in it's always welcome.

gary wrote:...I think one of the advantages of posting projects/circuits/software to the forum (and Newsletter) is the opportunity for peer review...

That is true. but does anyone want their errors made public prior to others 'in the know' at least having a cursory a glance at it? In whatever format it may take?

We all post things here that have not undergone the process of others checking it's a valid design/point/whatever. Witness Steve O, he's going to reproduce the wide-band LED driver I designed, complete with a PCB...what if I've made an error?

It's the old adage, "Publish and be damned."

Steve A,

Steve Anderson wrote:That is true. but does anyone want their errors made public prior to others 'in the know' at least having a cursory a glance at it? In whatever format it may take?

Certainly, if there are "others in the know", it is obviously better for them to have "a crack at it" first.

Alas, I think most of us work in isolation and this forum, or the newsletter is the first appearance of our work to the outside world.

Certainly, in the case of my software, there is little opportunity for peer review in the true sense of the word - there are not too many people willing to sift through reams of c++ code. It definitely is a case of "publish and be damned". But that's ok, it's published in the hope that it will be useful to someone, if it's not they don't have to use it. At least they won't have wasted a great deal of time or purchased expensive components etc. Having said that most mistakes are really just minor things that are picked up during debugging anyway. I suppose "newbies" have a bit of a hard time if it is an electronic circuit and they aren't "wizards" at it yet. But hey! that's what this forum is, at least partly, for isn't it? To help them that is.

AncientBrit wrote:That'll be the systems that produce petrol(gas) from water

Clearly neo-alchemy, there's no carbon in water.

If you want free petrol you should start with CO2 instead :p

M3DVQ wrote:Clearly neo-alchemy, there's no carbon in water.

If you want free petrol you should start with CO2 instead :p

Aaah yes, I remember now, the story goes: you fill your tank with water then drop a tablet in and off you go...

That tablet was obviously just an Alka-Seltzer

In an effort to reduce errors once I've done the first fag-packet sketch I cad the drawing, print it and build the prototype from that. An example is below (non-NBTV though).

As I build I highlight the components and wiring in yellow as I go, once testing is under way and things are working as planned then the semis get highlighted in green.

Where I make changes or additions I add them by hand to the printed version (e.g. R3 and the alteration to R4 & R5). These then are added to the software version as I do them. Other notes are added and also transferred to the soft version. What I end up with is an 'as-built' drawing that hopefully is error-free. In this case apart from the software issue being amended, it is finished in the second drawing.

Most build first and do the drawings later which provides the opportunities for slip-ups to sneak in.

You'll notice the generally grubby nature of the paper document as well as the water stain (actually beer) in the bottom right-hand corner. Accidents happen.

Steve A.