Last updated 06 March 2008
The power supply. (09/05/2004)
The power supply (PSU) is a 140w micro-ATX design, small but adequate to drive the motherboard, a network card, the hard-disk and CD-ROM.
I couldn’t find any figures for the efficiency of the PSU so, I measured the current draw on each of the supply rails (5v,12v, 3,3v etc) with a DC clamp meter. (multiplying the current drawn by the voltage of each of the rails, will give the power used by each rail) and estimated the power used at idle was 28.5w. Measuring the mains input gave a power input of 46w, this equates to an efficiency of about 62%.
The power supply (PSU) is a 140w micro-
I couldn’t find any figures for the efficiency of the PSU so, I measured the current draw on each of the supply rails (5v,12v, 3,3v etc) with a DC clamp meter. (multiplying the current drawn by the voltage of each of the rails, will give the power used by each rail) and estimated the power used at idle was 28.5w. Measuring the mains input gave a power input of 46w, this equates to an efficiency of about 62%.
With the CPU running at 100% the whole machine is drawing about 60w which means I have about 22w (60w * 38%) to dissipate in the PSU. I have not been able to find out which bits of the power supply dissipate the most heat but, clearly, the semiconductor parts at the most sensitive to temperature so, it makes sense to ensure that these part are adequately cooled.
It would be possible to remove the major semiconductors (i.e. switching transistor, diodes and regulators) from the PSU circuit board and mount and rewire them on a remote heat sink but, given the modest dissipation and small size of my PSU, I have removed the fan and added heat shunts (made from short lengths of 4mm thick aluminium extrusion) between the semiconductor devices to the two heat-sinks mounted over the fan orifice. I punched a few extra holes in the case just to let the air flow through freely.
The PSU is mounted at 90 degrees to normal to allow the heat-sinks to sit vertically and to clear space above the CPU heat-sink for a clean air flow. This has the slight disadvantage that the power connector now protrudes from the top! The PSU runs quite warm rising to about 48°C at full power.
25/02/08 - New power supply for P4 board.
The old 140w supply would not be adequate for the P4 so the new machine uses the 200w Upguards LC-B200SFX micro-ATX supply that I modified for use in my PVR project
It is bolted to a spare 1K/W heat-sink (identical to the one used to cool the P3’s CPU)
The mains lead no longer pokes out the top of the machine.
It would be possible to remove the major semiconductors (i.e. switching transistor, diodes and regulators) from the PSU circuit board and mount and rewire them on a remote heat sink but, given the modest dissipation and small size of my PSU, I have removed the fan and added heat shunts (made from short lengths of 4mm thick aluminium extrusion) between the semiconductor devices to the two heat-
The PSU is mounted at 90 degrees to normal to allow the heat-
25/02/08 -
The old 140w supply would not be adequate for the P4 so the new machine uses the 200w Upguards LC-
It is bolted to a spare 1K/W heat-
The mains lead no longer pokes out the top of the machine.
