Naked Science Forum
Non Life Sciences => Technology => Topic started by: syhprum on 12/09/2014 16:53:55
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Seventy years ago when I was making my living fixing radios one of the chief sources of annoyance was faulty valve sockets that were laborious to replace and good quality ones were difficult to obtain so one often resorted to soldering the valves in !.
In the present hi tech world where semiconductors and valves are reputed to last up to 50 years and disk drives to run 50,000 hours between failures connectors seem to get poorer and poorer , I have just spent about a day sorting out disk drives that got corrupted by loose connections.
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Not cost effective : more-robust connectors will cost more to produce , increase size and weight on a device which will probably be replaced for a superior one in about five years.
http://en.wikipedia.org/wiki/Moore%27s_law
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Some of the challenges for modern connectors are:
- Number of contacts: Higher data rates encourages parallel connections (such as on CPU chips). But this means more points of failure, and more force required to insert the connector.
- Small size: They have to fit inside smaller and smaller devices, which means less contact area, and any bit of corrosion or grit could break the contact. It also makes it hard to get good spring force on the contacts.
- Higher frequencies: They must carry square waves containing frequencies of a GHz or more.
- Impedance Matching: At these frequencies, electrical signals start to act more like sound waves than a steady flow of water, and any small impedance changes cause echoes and cancellation zones. The connector must be matched to the cables and circuitry on either side.
- Crosstalk: When high frequencies are carried in a small space, some of the signal "leaks" across to adjacent pins of the connector due to the capacitance between wires, causing interference. This often requires some form of shielding in the connector.
- Voltage & power: Today's high-frequency electronics runs off lower voltages and currents, so any signal loss in the connector will break the connection. This is especially a problem in low-power portable devices.
- Cost: Gold connectors are less likely to corrode, and provide wide contact area. But there is always cost pressure to reduce the plating thickness.
- Mechanical shock: Portable devices are subject to mechanical shocks, and connectors being inadvertently knocked out by the cables.
Some connectors have improved: It sometimes takes me 3 or more attempts to insert a traditional rectangular USB connector. Despite criticism at the time, Apple's symmetric USB connector has made this about 3 times quicker.
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If I compare the cable and connectors that connect the monitor to the computer with the cable and connectors that connect the motherboard to the drives the comparison is ludicrous yet a monitor connection coming loose will only cause a moments annoyance while a loose HDD cable can result in hours of work to undo the damage.
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With new higher-speed interfaces, error-detecting and error-correcting codes become more important.
By monitoring the error rate across an interface, degrading connectors can be detected (and potentially fixed) before they fully fail.
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Having just soldered up 4 pairs of relatively-new headphones from the Naked Scientists office, I'd say that I agree; we seem to inhabit a totally throw-away world these days. All of them had faults with the cables into the earpieces. Bad design leading to tension on the cables every time they are taken on and off. Yet the headphones I have from a decade ago are still going strong...
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Valves are another case in point when all glass valves were introduced in the fifties we had three decades of TV,s that had to be banged on top to make them work due to corrosion on the valve pins, the only ones that were reliable were the Russian ones that had gold plated pins.
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So I had my "dependable" Maytag brand washer just about five years, when it stopped running the first time. The repairman's $400 quote to replace the logic circuit board to fix it, basically gave me Carte Blanche to tear it apart to see if I could find a way to fix it myself for cheaper. I had never done something like this with a major appliance and online guidance was very valuable. I traced the actual problem to a faulty safety interlock reed switch. I don't know if you have ever seen a reed switch, but it is this tiny tiny resistor looking electronic component. I found I could bypass the switch to get the washer running. But I discovered that it wasn't the reed switch that failed, but the wire that connected it to the circuit that corroded and rusted through and just snapped off. This wire that snapped was so thin just a single strand. Soldering in a new more robust piece of wire to reconnect the reed switch to the circuit was the final fix. Put it all back together and buttoned up and the thing worked like a charm, safety interconnects intact. I had grown up with a clothes washer that lasted 25 years without a problem, but when I buy a name brand with a reputation for dependability it fails for a switch design with a piece of wire as thin as a strand of hair not really designed for the damp environment or the inherent vibration of a washer machine. If Maytag had designed the part with a five cent piece of wire instead of the half cent piece of wire, their reputation would've been intact. The machine finally gave up the ghost with a final clunk this past month...and I replaced it...with a Maytag.
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Join the Grumpy Old Men club.
I've always driven diesel Ford Mondeo Estates (Taurus Station Wagon, for those in a different time zone). Time was, the engines had mechanical injectors, just like an old tractor, and worked until the bodywork rusted away. The advent of dual-mass flywheels meant that takeoff was a lottery: too quick and the engine stalled, too slow and the clutch dsintegrated. Then came electronic fuel management and a host of other delights that could go wrong for no reason: the engine won't run fast and the "diagnostic computer" won't tell you which of the fifteen or so sensors is misbehaving, so repair is a matter of very expensive trial and error. Why do I stick with them? Because the seats are more comfortable than anything comparable, and you can put a double bass in the back.
And don't talk about washing machines in my presence. I'd rather bash my dhoti on a flat stone.
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My £30,000.00 BMW that I purchased 12 years ago that has not yet done 50,000 miles but the SSG gearbox keeps playing silly and dangerous tricks that no one seems able to fix to the extent that I am contemplating a new cheap car.
I had two BMW,s previously with regular gear boxes that ran over 100.000 miles with little trouble but although a SSG is sweet to drive when every thing works properly I miss my old 1300 cc VW beetle