Camera flash capacitors pack a punch

In the "Mailbag" section of the May 2003 issue, a comment was made questioning the claims made by Adrian Righetti concerning the power of the main capacitor in a camera with a built-in flash.

I am a camera technician and I can ensure you that the flash capacitor can pack quite a punch. It needs to so it can supply enough current for the flash. My fellow technicians and I always take extreme care when working inside "live" cameras because misplaced tools, or worse still, fingers touching the capacitor terminals can cause unpleasant results as experienced by Adrian.

When working on cameras, we discharge the capacitor using a standard domestic 60W light bulb fitted with two wire leads and probes. The bulb glows briefly as it safely discharges the capacitor.

Michael J. Murphy,
Camera Clinic,
Collingwood, Vic.

Copy protection a nuisance

I'd like to comment on K. Poulter's letter in the May, 2003 issue of SILICON CHIP.

I do agree that copy protection is not a good thing for the general public. I purchased a number of CDs from EMI that use a technology called "Copy Control". I am not sure how this works but the CDs will not play in the CD player I have in one computer and only sometimes play in my car. Yet I have still succeeded in making perfect copies of these CDs and also ripping them into high quality MP3s (all for personal use). The technology only makes the product inferior for the average user; it will not stop a savvy user from copying the music at all.

Macrovision copy protection is also a problem. I have a relatively new flat screen television. I notice that the copy protection causes the picture to flicker in brightness horribly when darker scenes are playing. I have disabled all of the picture enhancement functions in my TV and DVD player but the problem still exists. If I disable Macrovision in the output of the player, the problem disappears.

I am a very experienced computer user. I have at my disposal the experience and the technology to pirate almost anything. It doesn't mean that I do. I pay for what I really like and if I wouldn't pay for it, then it's really not worth me having anyway. I believe that most people are the same. It's only a small minority that want to get everything for free.

Adam Hawes,
via email.

Making cutouts in plastic boxes

I noted the letter in Mailbag (July 2003) concerning the reader having difficulty cutting rectangular holes in plastic boxes.

As an electronics enthusiast I had the same problem and like Keith Anderson from Tasmania, I could do something about it. I personally redesigned our range of popular Jiffy ABS boxes so that there is now a pre-scored grid inside the lids. This gives the option of a large variety of rectangular hole cutouts.

You can simply use a sharp hobby knife to cut all the way through the lid. The result is an accurate hole perfectly aligned to the edges of the box.

Gary Johnston,
Jaycar Electronics.

Electrician's licence does not guarantee safe work

I have been following the debate on the need to have an electrician's license to do electronics work. Recently, I purchased a split system air conditioner from a large local electronics retailer. They arranged for the installation by a licensed electrician. I was unhappy with the installation and am still annoyed. Some of the problems were:

(1) Damaged brickwork on the wall where a new earth stake was installed. This presumably happened when the stake was being hammered in. Seven bricks were damaged. This damage would have been easy to avoid by placing a piece of timber or cardboard against the wall.

(2) The new switch for the air conditioner was loose when installed in the power box. It appeared that the self-tappers used to attach the switch had stripped their threads after being over-tightened.

(3) The power cable in the ceiling was not installed according to the official wiring rules, (AS/NZS 3000: 2000), as I understand it. The wire ran unprotected across the ceiling, where it could be walked on. The electrician blamed the apprentice, a statement which opens a whole can of worms.

To correct the matter, after I complained, the electrician cut the existing cable in the middle and added an extra length of cable using two junction boxes. This allowed the wire to be rerouted. This is contrary to the book "Electrical Wiring Practice" by K. Pethebridge and I. Neeson, 3rd Edition, Volume 1, page 86, McGraw-Hill, 2002, which states "Arguably, the most vulnerable components of an electrical installation are the electrical connections. For this reason, it is good wiring practice to arrange an installation with as few connections/joints in the cable as possible".

I conclude that this licensed electrician does not follow the rules and in any case, when challenged, does not adopt good wiring practice, even when relatively large currents are involved.

(4) Apparently, while the air conditioning manufacturer has no policy regarding the attachment of air conditioning units to Gyprock wallboard, the current unit was attached to the wall using hollow wall bolts (similar to toggle bolts), where the wallboard bears the weight of the air conditioner. The Gyprock company informed me that they definitely discourage this type of installation. It would have been very easy at the time of installation to attach the unit to the wall studs, which would have provided much better support. The electrician informed me that the use of hollow wall bolts is common practice.

I have further problems with the installation but enough has been said. Having a licensed electrician do the installation has not in any way assured me of good or safe workmanship. Quite apart from having requisite knowledge, so much depends on the individual doing the work.

Where has pride in workmanship gone?

Name and address withheld at writer's request.

Quartz halogen lamps and UV light

Your editorial about the inefficiencies of low voltage halogen lamps (June 2003) happily coincided with my reading a book entitled "Why the Watermelons Won't Ripen in Your Armpit" by one Ben Selinger, noted on the cover as being a leading chemist and science populariser. In a section about UV lighting in discos, he makes the following observation.

"The quartz halogen lamp operates at a higher temperature than conventional globes and produces ultraviolet radiation which its quartz envelope lets out. In the midday summer sun, the recommended daily exposure for UV is reached in about 15 minutes. At 25 centimetres' distance (one foot), a 50-watt quartz halogen globe without filter can deliver the same amount of UV in about 15 minutes. This increases to 40 minutes at 50 centimetres, two hours 40 minutes at 100 centimetres, and a full working day at 175 centimetres (inverse square law)."

Also coincidentally, my daughter mentioned that she and her husband were contemplating fitting a quartz lamp over the top level of a bunk bed, to do duty as a reading lamp. I need hardly spell out what I thought of that idea!

I find it very frustrating that remarks such as yours and of Mr Selinger are only read by a very small section of the community. They are, in my opinion, matters that should be given much wider publicity, along with a lot of other information that should be of concern to all of us.

I. R. Anderson,
Albany, WA.

50 years of electronics magazines

Can I say how important SILICON CHIP is to me. I purchased my first "Radio and Hobbies" copy over 50 years ago, in May 1953. It was the very first book I ever purchased and was the only technical thing I had ever seen.

Nobody I knew understood anything about such things and it was without doubt the beginning of my technical life. I went on to study engineering and read for a PhD at Cambridge on a scholarship. I became a civil engineer but I have never lost my interest in things electrical.

I still have almost ever copy of R&H and the rest of that series and of SILICON CHIP. Forgive me if I think of the two publications as one Australian popular electronics magazine. I read recently a high-level US technical national planning group noted with concern the demise of the electronic hobbyist. They went on to say they believed such activities were very important initiators of vocational paths that were themselves vital for the technical soul of a nation.

I think R&H started me along such a path and I am sure many other readers will relate to what I am saying. In that context, SILICON CHIP is in elite company as I don't think there are many publications like yours anywhere in the world still running and with such a long history.

For almost the full 50 years mentioned above, you have always had a story about servicing. I would purchase SILICON CHIP for this article alone. You seem to find folk who can tell these wonderful stories. My experience is that these two things rarely go together so what comes out each month is even cleverer.

It was rather sad to read the critical remarks in "Mailbag" in the June 2003 issue, about the work habits of your current writer and I was delighted to read the rebuttal and justifications offered; how logical, reasonable and measured.

Can I also comment on the honesty of your current writer? I think everyone who fixes things does things which they later realise were not so smart; like discharging a capacitor by making a transistor conduct with your multimeter and taking out half the board. I can relate to that so very well. Yet I wonder how often I have admitted such follies to myself let alone writing about it in a national publication.

Your current "Serviceman" writer is so refreshing! All of the writers and especially your current writer have provided me and I imagine countless others with endless enjoyment and a great deal of fault-finding wisdom. There are so many lessons to be learnt from fixing things that go far beyond what has actually been gained by whatever it was that was fixed. I have much admiration for people who make a living out of it.

Kenneth E. Moxham,
Urrbrae, SA.

Digital TV is impractical

As a collector and restorer of vintage B&W TV sets, I've been following the "analog TV switch off" question with interest and I am in total agreement with your July editorial concerning the failure of terrestrial digital TV.

There are two points which seem to be conveniently ignored by those trying to force it upon us. The proponents of Digital TV seem to think that we will view it via a large screen TV in the living room (hence the additional push for high definition).

Coming back to reality, a typical Australian house has more than one TV. If the analog signal is switched off, each of those sets will require a digital decoder. For a house with four TV sets, the cost to equip them all with decoders is already around the $2000 mark. The proponents may say to feed all the sets from one box. That's fine if everyone wants to watch the same channel but that's usually not the case. And if someone wants to record a different channel, that means yet another set top box for the VCR.

The second issue of concern is with portable TV sets. How am I meant to use my miniature battery (rechargeable, of course) operated TVs? Am I meant to wear a backpack containing a 12V battery, inverter and digital decoder just to watch my pocket LCD TV set when I travel?

The fact is there is no valid reason to switch off our analog TV service. We are fortunate in having the 625-line PAL system in Australia. It is tried, proven and inexpensive technology. With a decent aerial and a properly adjusted set, it is very hard to fault it.

The sensible option would be to keep digital for pay services where interactivity and multiple channels may justify it but leave the FTAs as they are.

On the subject of domestic halogen lighting, apart from the gross inefficiency, the thought of a hot transformer hidden away in the ceiling catching fire is enough to put me off. That's not to mention the UV radiation.

Finally, has anyone noticed that, sadly, 240V incandescent light bulbs are no longer made in Australia?

John Hunter,
via email.

Blue glow in valve not a death sentence

I would respectfully take issue with you regarding the answer you gave in the July 2002 issue (page 91) to R. R. of Ocean Reef, WA, about discharges in valves.

In a rectifier such as an 80, a mauve to pink glow between the filaments and the plates definitely indicates a gassy tube and it is indeed kaput.

On the other hand, a blue fluorescent glow on the mica supports or the inside of the glass envelope indicates a very high vacuum and a good tube. This phenomenon was also apparent in output tubes when it could be seen fluctuating with the signal. It made a very striking display with the nice contrast between the (electric?) blue of the discharge and the red glow of the heaters or filaments. This pretty display was probably the only advantage that valves ever had over transistors!

Alan March,
via email.

Blue glow in valves OK in some cases

In your reply to R. R., Ocean Reef, WA, in the June 2003 issue, you state that "Any valve with a blue discharge is gassy - it's kaput".

This situation is generally the case where the blue discharge is between the elements of the valve. However, a blue fluorescence on the glass which pulses with the output and often seen on the larger output valves such as 6L6-Gs, 807s and the like, is indicative of a good valve with high vacuum. Less common would be gas-filled rectifiers such as the type 83 in which the gas ionises during normal use.

John H. Wark,
via email.

Visions of the future

Since buying a USB flash memory card recently, I have been having visions of the future while playing with my new toy. The cost at present is about $500 per Gigabyte. Soon it will be $100/Gb. At first I imagined booting up any computer with my own data. But why not the operating system as well?

All those bulky drives, CD, HD, etc, are for the chop. Why not a 10cm cube black box with power and the CPU, to which peripherals can connect? These could be spread all over the world. Why not have all this in a flat-screen monitor in homes, cafes, libraries, offices, schools, telephone boxes, transport, etc? Plug in your USB card and you're away! Costs would be small and go automatically onto your credit card. Sufficient security would be provided by built-in voice operation.

Jim Jacobs,
Engadine, NSW.

Share this Article: 

Digg this story

Seed Newsvine

Post to Reddit

Save on del.icio.us

Email