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Salvage It! By BRUCE PIERSON Harvesting a Dead PC Motherboard for Parts Last month we looked at the goodies we could salvage from a dead PC supply. But what about the motherboard? There’s a lot of useful parts on there, too . . . but getting them off sometimes proves difficult! I t’s estimated that the average life of a desktop computer these days is little more than two years. After this time, its performance can be agonisingly slow compared to “the latest and greatest” to the point where, if it is being used in a business environment, it is likely to be actually costing money – merely in “wait” time. Even worse, it is probably not able to keep up with the latest software. Or consider the other scenario: your computer has “died” – the power supply still works but there is an obvious motherboard failure. In either case, your choice is to either replace the motherboard (along with memory, probably a new hard drive, etc) or simply replace the whole thing. Financially, replacing the motherboard is often the best solution (though not always!), so let’s assume you’ve gone that route and in the process, ended up with an old one. You could just discard it, or you could wreck it for parts and get a bunch of useful components from it for the junk box before tossing the skeleton. What parts can you salvage from a dead motherboard? Well, it depends on the type of motherboard you have to start with. We can categorise motherboards into four broad categories. (We’ll forget about really old types!) (1) Older motherboards that use SD RAM. These boards tend to have more, smaller sized and smaller value electrolytic capacitors of a higher voltage, typically 330F 25V, no USB headers and not much in the way of heatsinks (if any). (2) Not-quite-as-old motherboards that use DDR RAM. These boards usually have several physically larger electrolytic capacitors of higher capacity and lower voltage, 82  Silicon Chip typically 2200μF 6.3V and a number of smaller capacitors, USB headers and inductors. 3) Newer boards that use DDR-2 RAM. These are similar to the DDR boards. 4) Newest boards using DDR-3 RAM. These usually have solid capacitors of smaller physical size and sometimes a few of the older electrolytic capacitors, more heatsinks, more choks and more headers for USB, fans and other connectors. The photo above shows a typical older motherboard that takes SD RAM. This was the only dead motherboard available for “harvesting” at the time of writing, so it has been sacrificed for this article. Motherboards are multi-layer fibreglass in construction, with layers of track-work buried inside. With platedthrough holes, de-soldering components can be quite difficult, due to the heat transfer through the multiple layers of track-work throughout the board. So, how do we remove the components? Well, components with only two leads, such as capacitors, can generally be removed with a 40W soldering iron, by heating each lead in turn and bending the component gently to the side after the solder has melted. This procedure is repeated several times, until the component is free. However, this method won’t work for multi-lead components, such as ICs or header pins, etc. A blowtorch to the belly motherboard The best method I have found for releasing such components is to use a small gas blowtorch set on the lowest siliconchip.com.au level possible, with the flame angled across the board, in order to melt the solder and minimise heat transfer to the components. If you are using this method to salvage parts, you need to take a lot of care and proceed in a manner so as not to endanger life or property. Firstly, it should be noted that using this method produces a lot of smoke and the board will often catch fire during the procedure. However, this presents minimal risk to the salvager, if the proper precautions are taken. It goes without saying that this procedure must be carried out outdoors in a well-ventilated area, away from flammable material. Make sure you have a bucket of cold water on hand in case of burns (or fire!) and wear safety equipment: insulating gloves, protective glasses and so on. Quite often, small SMD components may “explode” off the board and be projected in any direction and the last thing you need is an extremely hot component landing in your eye. Overheated “normal” components can also explode. It sometimes happens that a ball of solder will drop from the board, so make sure you don’t get in the way, nor have any skin exposed. Remember, this solder will be very hot – hotter than you are used to with an iron – and can make quite a decent burn hole in your skin (and/or clothes). Hot air gun alternative An alternative to the blow torch (and an arguably safer) method) is to use a hot air gun, (a real one, not a hair drier!) set on high heat. It is a slower process and can actually heat the components even more than a flame (due to the fact that the heat must be applied for longer). Hot air guns are still quite capable of heating a PCB to the point where they catch fire and can, of course, also cause you damage if you get in the blast! Another possibility is an SMD re-work hot air station but not many readers are likely to have one of these! Removing connectors When removing items such as USB headers and IDE connectors, it’s a good idea to plug an old cable into the header. This helps to minimise the heat transfer to the plastic base and keeps the pins straight and aligned, as well as providing a convenient “handle” to remove the header with. After the header has cooled, it can be removed from the cable and stored for future use. USB headers are handy when making a power supply and fan connectors can be added to a project to enable the use of a computer fan in the project. Depending on what motherboard you start with, you will most likely end up with a different assortment of components to those shown above. The above selection is somewhat minimalistic, due to the age of the board that was wrecked. A better selection of components will be obtained from newer motherboards. However, we salvaged the following components from this exercise, so it was still worthwhile. The alternative would have been to bin the dead motherboard and all those components would have gone to waste: 1 ceramic capacitor 2 large inductors 1 small inductor 1 header strip 1 battery holder 1 battery (probably dead if it’s an old motherboard) 5 3-pin headers and 5 jumpers to suit 1 20-pin power connector (not overly useful!) 3 transistors of unknown type 1 32-pin IC socket (great if you have any 32-pin ICs!) 1 PROM (useless unless you have an identical motherboard) 1 floppy header (what is a floppy?) 2 IDE headers – these can be used with cables to connect PCBs 1 8-way DIP switch (not usually found on newer boards) 1 dual USB port 1 crystal (unlabelled but probably around 8MHz) 2 serial ports and 1 parallel port – probably not much use for anything? 1 fan connector which can be used in a project to plug in a fan Various screws and nuts A bunch of SMD components which fell off by themselves in the process of heating the board. (They could still be useful later if you can identify them and test them). As with all salvaged parts, be sure to test anything before you use it for a project or a repair. If you don’t know a component is good, don’t use it, because it could be faulty and you don’t want to be introducing faults into a repair or a project and causing unnecessary problems. After the one we stripped for this article we also acquired a newer motherboard (shown below), using DDR-2 RAM. It has a much better selection of parts than the old one. The number of electrolytic capacitors is much greater and there are USB headers and more fan connectors. As yet it’s still intact, as this board is still in working order – even though it is an older board, it could still prove useful SC for a repair or an upgrade of something even older. 25 Electrolytic capacitors, mostly 330F 25V (a better selection is on newer boards), 1 3A diode 2 1A diodes (which fell out by themselves) siliconchip.com.au February 2014  83