Fanless computer / 0dBA Project rev. 2

    Power supply unit
    I must admit that I came in nowhere with the power supply unit. As I’ve said, the initial plans to manage without hand-made components failed because of absence of Zen on sale. As a result I had to lose myself into reading reviews for some days. I chose the top model of Epsilon – the correlation of its price, quality, power and coefficient of efficiency was better than in competitive models. Why have I chosen such powerful supply unit for the system not demanding much energy? First of all, I took it to “grow into” – there are reserves for enlargement of radiators area even now. Second, I made this to move away the boundary of temperature stability: in theory, such power unit could provide the required 250 watt even being heated up to 100°. But this was in theory… In practice the power unit construction had some “delayed-action mines” which were not mentioned in the reviews, and because of them all my calculations became unavailing... The first “present” of its creators lied in the fact that transistors of high-voltage section were screwed directly to the radiator, without standard in such cases dielectric spacers. Perhaps, this positively affects the heat sink, but this adversely affected my power unit. As I didn’t expect such unpleasant surprise from FSP, I without dissembled thought got into the device with thermocouple in order to measure the temperature of radiators and accidentally short-circuited one of them on the case. In a second I lost two power units. I lost two units because high-voltage power surge affected the net and the main computer was endangered; at that time it was 0dBA rev.1. Fortunately, I didn’t have to make Powerman anew. I merely changed safety device. The Epsilon examination showed that it passed away to the world of evercold processors without a return ticket. There were burnt channels, SMD-components slithered down from their places… I could give it up as a bad job and find a new object for pacification, but not on the cards – the construction had already been elaborated and illustrated, the component parts had been bought and I was too lazy to redesign the construction.  I took the same but less powerful unit – the 700s had also disappeared from sale by the moment. In a week I had such a device.

 
    Cooling is made in the same way as in Powerman from the rev.1 with the only difference: radiators here are composite, not cast. Presence of 300V in two out of three radiators demanded correction. As the edge radiator is placed near the wall, I didn’t expend the pipes (again of Tt Schooner) on it – I lengthened it with a patch on radiator. I pasted thermal block for two pipes, made of copper halves of several schooner type, to the neighbouring radiator (also flat, finless and under tension). I implanted the pipes into the biggest radiator in classical way; but the finning was too thick and I had to treat it in barbarian way: I took away the board, rest the edge side of radiator against the window-sill and carve out one fin from every side with a thin chisel. Taking into consideration the fate of the first power unit, I used rubber washers-spacers in the place where the pipes passed through the grating, and skewered the radiator plates (which I took off СМ Blue Ice II) in a staggered arrangement in order the fins of “dangerous” radiator didn’t touch the fins of “safe” radiator. The case of the unit had been preliminary cut in thick nearly in one centimeter: it fitted between the video adapter and side cover, but very close, without gaps – as a result video adapter was locked in a non-ventilated pocket. In general, the device turned out to be frightful in terms of taking it with hands, but quite runnable. And there we discovered the second “mine”: the unit had unmentioned in the reviews overheat protection which switched it off when the temperature exceeded 55°C. What for did I overpay for the 600 watt device? To the point, I haven’t solved the problem yet, as nobody can understand how this protection is realized and whether it is protection at all and not a by-effect. The power unit sustains the load from computer in the air temperature range up to 25-30°C, but in extreme hot weather it switches off when playing the games and we must add a cooler.