Even fanless bricks can and do make noise!
It's the transformer, itself, that's buzzing or humming. The internal mount has come loose, is deteriorating, or the transformer is just a cheap unit to begin with.
Strangely, the 4-pin 12V CPU adapter from mini-box that the Athlon and Pentium M's need only comes with bare pigtails.
I've actually found the reason for this. Upon close examination, the PW-200-M (but not the picoPSU-120) has a set of four empty holes on the pc board connected in parallel with the output lines. The idea is that P4 or Athlon users who need the extra 12V connector can solder the pigtails directly into the board. Of course, this assumes that the pigtails are long enough to reach the 12V socket, which may not be the case. In fact, the the power input lines on the PW-200-M aren't even long enough to reach the back of the case where the socket needs to be mounted! In order to install the PW-200-M the way it was intended, I had to replace the two 6-inch wires with 18-inches wires.
The real problem with the PW-200-M that mini-box.com sells
is that because of it's right-angle layout, very few boards will accept it directly (BTW, two MBs that will are the AOpen i855GMEm-LFS
for Pentium M and AOpen MX3S-T
for Pentium III). To make matters worse, even though an extender cable is available, there are no mounting holes on the pcb. However, it turns out that the same PSU is available on a long strip
with holes designed for mounting inside a case. You'll have to add a pair of stand-offs, as well as an extension cable adapter, but it's a much better solution for a lower price (USD $45). It's the model called PST-ITX-3
and they say it comes equipped with a 4-pin 12V connector.
In any event, paired with the right brick, the picoPSU-120
is a more elegant solution, since you can use it with virtually any board available.
Update (19 Aug):
In doing a direct comparison between the PW-200-M
and the picoPSU-120
(same motherboards and drives, same 80W AC/DC brick), there is no difference in power draw at the outlet. Given the dearth of fanless bricks above 100W, the picoPSU-120
still seems to be the best choice in low power PSUs.
Update (11 Sept):
Having now purchased and installed the 100W brick from Mouser (mentioned above), I can verify that it works perfectly with the picoPSU's. Its only real drawback is it's price.
Also, mini-box does sell the long strip version of the 200W PSU mentioned above. They call it the model PW-200-V
. The main reason to mention this is that I have one motherboard, a PC Chips M599LMR
for socket 7 CPUs, that was unstable with the picoPSU-120 (the system kept rebooting for no apparent reason), but which works perfectly with the 200W version. Considering that the PC only draws 50W (with a 550Mhz AMD K6-2+ CPU installed), it's not clear why this should be.