Motherboard capacitors need to be tiny

I read your article about the explosive motherboard capacitors, in the May 2003 issue. Unfortunately, I read it a little too late. I manage the network for an Internet cafe and I recently (a month ago) diagnosed the capacitor problem on 20 of our motherboards. You have covered the problem but not enough about the solution.

You mentioned the low-ESR capacitors you can buy from RS but unfortunately they were all too big to fit on these boards (about 20 capacitors need replacing per board). I imagine most motherboards will have a similar problem as everything is squished in as close as possible.

After many interstate phone calls and confused sales people, I found a suitable replacement. The Rubycon ZLH series provide a range of 1500μF capacitors which I managed to be able to get in an 8mm package. See www.tenrod.com.au for contact details. The capacitors cost 60c each but minimum order quantities are a problem.

Aaron Russell,

via email.

Mars Rover should have dust wipers

After reading the article about the Mars Rover mission, I almost fell off my chair when I read that the mission must ultimately end after 90 days because of dust accumulating on the solar panels. There might be other reasons why the mission will not last forever but it certainly should not be because of a bit of dust.

Why are there no simple dust wipers to keep the panels clean? Ultra-light wiper arms carrying carbon fibre bristles, similar to those used to get the dust off LP records, could avoid a billion dollar project becoming useless after only 360 duty hours. I don't see much chance of it discovering anything significant in the 13km it is proposed to travel in that time anyhow.

The wipers would move slowly (1cm/s) across the panels once an hour to avoid dust build-up and run a little bit over the edge so the collected dust could be removed from the bristles. Only tiny motors would be sufficient for this purpose and they would only be needed for about one minute per hour. Their power consumption would be negligible compared to the power gain achieved by keeping the panels as clean as they were on day one.

The six motors and wiper arms would probably mean an extra 500-1000g in weight depending on how ultra-light they can be built. I have sent a letter to NASA making this suggestion.

If NASA can't fit the wipers in time for the second launch at least, I honestly believe the second Rover should be postponed until the next opportunity in 26 months, instead of blasting useless billions into the sky.

Peter Mendelson,

Coffs Harbour, NSW.

Comment: that's sounds like an excellent idea, Peter. Bloody brilliant, in fact! Obviously, NASA needed some Aussie ingenuity long before this.

Neat process for plastic boxes

I'm not sure if it is correct etiquette to give free plugs for advertisers in your magazine but I am pleased to have found a solution to a problem with plastic boxes.

I have been looking for a good way to cut rectangular holes in plastic boxes, accurately aligned with the components that need to fit through the holes. I asked several experts but the job seems to be surprisingly difficult. For businesses specialising in signs, the box was too high, while for those specialising in furniture, it was too small. One could accept files only in a very old version of CorelDraw.

Some people seem to be able to do it successfully with a mini drill. When I tried this and when I showed my handiwork to my friends, they asked, "Why did you use a chainsaw to make such a tiny hole?"

I have now developed a procedure that works impressively well whereby the holes are cut by my PC board maker, Instant PCBs. I pretend that my box is a (peculiar) PCB and prepare the artwork for the hole(s). I send the file by email and the box by snail mail to Instant PCBs. They send back the box with very clean, very professional holes, located to PCB precision.

Because we both use PCB software, then any shape that can be cut into a PCB can be cut into the box and I don't need to learn the idiosyncrasies of yet another software product. And there is no hint of a chainsaw!

Keith Anderson,

Kingston, Tas.

Comment: inquiries about this process can be directed to George at Instant PCBs. Phone (02) 9974 1189 or email instantpcbs@aol.com

Pointers for home entertainment PCs

I have some feedback on the "Silent Running" article in the April 2003 edition of SILICON CHIP. The author of the article mentioned using a silent-running PC as part of a home entertainment system (MP3s and DVDs). The following information may be helpful to others, as I have done some experimenting in this area.

To play DVDs successfully with no jumping or "micro freezes" with a software DVD decoder (such as WinDVD or PowerDVD), a 1GHz minimum processor is required regardless of type (AMD, Intel, etc) as pure maths processing power is needed (950MHz produces some jitter). If a hardware decoder card is being used, then processor power is irrelevant.

The minimum graphics requirement is an Nvidia TNT2 32MB card or similar and it must be an AGP version, as the PCI slot cannot provide enough data transfer speed. Preferably, the graphics card should have a TV output and you should use a TV-out interface program that enables the use of keyboard shortcuts to enable/disable the TV out, as the monitor usually produces no picture when TV out is being used. The TV is generally in a different room as the computer fan is too noisy. I use "TV Control Center" (TVCC 2000) or "TV Tool".

When decoding DVDs, the processor operates at 100% and the temperature can rise considerably after awhile, so efficient heatsinking is required. To play MP3s successfully (no skipping or jumping), you need at least a 133MHz Pentium or 586 processor. I found it best to use a DOS program (MPX Play - available free from the web), as the boot time of the computer is much reduced.

If you must use Windows (to run Winamp, etc), it is best to use Windows 95 as the program overhang and thus boot time is reduced - as well as lower system requirements. If you use Windows 95A instead of Windows 95B, there is a 2GB limit on the size of the hard drive (as well as no access to FAT32 formatted drives greater than 2GB).

If the processor speed is less than about 500MHz, then the age of the motherboard may come into play if a hard drive greater than 8GB is used (some motherboards have an upgradeable BIOS though). If the size of the disk drive is an issue, it can be partitioned into 2GB or 8GB partitions, or you can use the appropriate "boot loader" or "disk master" program to enable oversized disk drives to be used. The VIA motherboard mentioned in the article does not have this problem.

Philip Chugg,

Rocherlea, Tas.

Halogen lamps waste resources

I was pleased to see that at last someone has raised the issue of the proliferation of low voltage halogen lamps. While I totally agree with what you have said in the June 2003 "Publisher's Letter", you overlooked one important aspect. That is the huge waste of natural resources (copper and steel) that goes into the heaters, sorry, transformers to power these things.

Sure, low voltage halogen lights may be "trendy" and offer interior designers more creative answers but a plain old incandescent light is cheap, technically dead simple, and only needs a pair of wires connected to the 240VAC mains to operate.

Leon Williams,

via email.

Filter for sound card interface

I am writing in response to the letter in the "Ask Silicon Chip" pages in your April 2003 issue about the noisy sound card interface. I also built the EA project and found it very noisy. The noise was coming in on the 5V supply from the computer.

The sound card interface has a filter capacitor on the supply line but needs some series reactance to be more effective. I experimented with various chokes in series with the 5V supply from the computer but found that a 1kW resistor reduced the noise to an (almost) acceptable level without reducing the voltage too much.

Mike Hammer,

via email.

Old wireless sound deficient in bass

I have just read your "Ask Silicon Chip" (March 2003) suggestions in response to reader R. W.'s query (Reproducing Old Wireless Sound) about how to reproduce a "wireless" sound from the 1930s for his amateur theatre company.

Your comments make a lot of sense but if I may, might I suggest in addition to limiting the top-end frequency response to 5kHz as you say, you would also impart a lot of realism to the "wireless" sound by rolling off the bottom-end response starting at, say, 300Hz. The old speaker transformers in the 1930s radios were fairly hopeless at the low end too and this I believe was a major limiting factor for reproducing low audio frequencies in the average home wireless.

Stan Hood,

Christchurch, NZ.

Comment: the bass response depended more on the cabinet than the loudspeaker transformers - some were really quite good, particularly the bigger console radios. However, there would not be much output, if any, below 100Hz.

Vintage radio speaker repairs

The Vintage Radio column in the April 2003 issue mentioned repairing tears in speaker cones. I've used another method for some time now and had success every time.

What I do is cut a piece of supermarket shopping bag to the correct shape to cover the torn cone area (this works if it's basically intact, with no pieces missing) and glue it to the rear of the cone. The glue I use is a "never drying" vinyl floor adhesive which was made by Carson Adhesives in Brookvale who recently sold out to Bostick. I believe they are continuing the Carson brand of adhesives.

The type number is Carson 698 and it is also very useful for "doping" and also repairing silverfish damage to the outer surrounds of conventional paper/cloth surround speakers, as it bonds to paper very well. "Doping" the outer surround makes all conventional speakers much "tighter" in their sound and improves the low-end response.

I've even "doped" old MSPs and Magnavoxes and the improvement in the sound is just amazing.

Brad Sheargold,

via email.

DVD aspect ratios are stupid

Back in the February and March 2001 issues of SILICON CHIP, I read with great interest the letters in "Mailbag" about aspect ratios, even though I didn't understand it all. Because I then didn't own a DVD player, I forgot about it. That is, until yesterday when I went out and bought a new TV (68cm, 4:3 ratio) and a DVD player.

I keenly put my first disc in, pressed PLAY and was confronted by a stupid-looking narrow strip of colour across the middle of the screen covering about 50%, with very large black bars top & bottom. This was 2.35:1.

Now I may be dumb but I have three questions. I can understand the reasons behind 16:9 (mind you the TV sets are still quite expensive, because you need a reasonably large one to look good) but why on earth would anyone produce a DVD aimed at the home user in a 2.35:1 format? I believe not one TV on the market can display this properly, without black bars.

It seems like another case of big companies telling us what we are going to get, even though the vast majority of us still own and buy 4:3 sets. I won't even mention the cropping they do to "reformat" to some ratios.

Also some discs have a section saying "16:9 transfer dual-layered format layer transition may trigger a slight pause". Does this mean it can also be played in 16:9, without stretching everything out of shape?

Is there a way of ripping the disc, then reformatting and burning a new copy to at least 16:9? It doesn't look too bad on a 4:3 set.

Anyway I'd better stop writing, I'm getting angry again!

Neil Smith,

via email.

Comment: we don't blame you for getting angry. 2.35:1 is such a stupid ratio. Nor are there any practical answers to your questions.

Batteries are sometimes preferable

While I agree with the broad sentiments expressed on batteries in the Publisher's Letter in the May 2003 issue, I have to disagree with your qualified suggestion to use rechargeable batteries or plugpacks wherever possible.

I provide toy repair services to a number of organisations in Victoria which serve physically and intellectually disabled children. Battery-operated ("switch") toys, often sophisticated and expensive, are used extensively for therapy, intellectual stimulation and entertainment. Many of these toys incorporate motors, LEDs, LCDs, logic and sound modules, often imposing a substantial current drain. However, battery operation is a valuable feature, permitting use of toys both indoors and outdoors, independent of AC mains supplies.

Operation from plugpacks presents potential safety hazards in a classroom environment. Extra supervision would be required to cover disabled children who habitually chew through the insulation of low-voltage leads, and to monitor plugpacks for inadvertent overheating and possible fire. In addition, there are traffic hazards where leads are festooned around tables and wheelchairs.

Finally, plugpacks may not be electrically compatible with the power supply (or multiple supplies!) required for toys, leaving batteries the only option.

However, there are a lot of questions surrounding battery use. For example, why do toy manufacturers advise "Do not use rechargeable batteries" on the packaging? Does this only refer to nicads? Despite accompanying graphics, battery descriptions such as "super heavy duty", "heavy duty", "long life", and "general purpose" are confusing to consumers.

What about "rechargeable" batteries (eg, nickel-cadmium and other "exotics" such as NiMH)? I assume that safety concerns for children arise from breaching of the case and in the case of nicads, release of highly toxic cadmium and alkali which may cause eye damage and skin burns. This may result from unintended overcharging but perhaps elevated temperatures or mechanical abuse can contribute? Manufacturers also warn that rechargeable batteries should be kept out of the reach of children. This is not necessarily controllable with some children!

Your suggestion to use apparently "dead" batteries in low current devices such as clocks and remote controls is sensible. I do this regularly. However, many toys and other devices are voltage sensitive and may present operating problems. I hope also that people are not encouraged to reuse "old" batteries in smoke detectors! If the battery reuse option is pursued, use of a suitable (loading) battery tester rather than a mere voltage check is absolutely vital.

Brian Graham,

Mt Waverley, Vic,