Comment on 'boardswapping' as part of the computer culture.

I'll wade in with my comments now....... Board swapping is a useful method for high reliability systems (I work in air traffic control engineering), and leads to a very high availability of the system, especially when coupled with high levels of redundancy, we use the "three level" service/maintenance regime that has already been discussed. However, for the system to provide the required levels of service, it needs a serious investment in spares, logistics and training, for example: Spares. All spare boards in the system must be tracked to a known state of serviceability and modification - as Tony has pointed out, just because it says the same thing on the box, it isn't always the same! Logistics. You need to have the right parts in the right place at the right time - because of the different skills required for 1st, 2nd and 3rd level repair, at least the 3rd level, and often second level workshops are of site. You need a good stores and transport system to move the stuff around fast, and to track where it is (a computer is NOT always the answer....). You also need an organisation to keep the repair centres fed with the correct spare components, and to provide a "lifetime buy" service for components which are about to become obsolete (I know of some systems that are nearly 40 years old, and are kept at extremely high levels of service with this kind of service). Training. Even the first line technicians need a high level of training, you have to be able to interpret the fault symptoms and work out which board to change. I have some system training so ingrained that I can diagnose faults over the phone 10 years after I last worked "hands on" on the equipment. Now back to our systems! With the above in mind: 1. we rarely know the state of any parts we have - a board that has been un-used for 20 years is quite likely to be faulty! 2. We are self trained on these systems. If we can narrow a fault down to a board, we can often take it down to the component. 3. We are lucky to have any spares! Looking at a less than vintage system, for the most part, it is difficult if not impossible to go below board level ( I can sympathise with Tony here), and nigh on impossible to get information on how that board is working, or even get test equipment that can capture the signals involved (I have a 100MHz (valve) scope with a 4 trace plug-in, or I can borrow a very old logic analyser from work). At this point, we are reduced to board swapping as the only option, though often with little measurement to back it up - the only thing we have over the teenager in PC World, is that at least we have a multimeter and can check the power supply voltages........ We are also at the point where PC components are so cheap they are not worth repairing - I can buy a LAN card for less than ?10. It costs me more than that to pay an engineer to replace it, let alone try and repair it. Even the kid in PC world expects ?5 an hour - if you try and charge some one ?50 for changing a LAN card, you'll soon be out of business I'll duck know. Jim.