[Amps] Resistors

[David Kirkby]

Ian White GM3SEK wrote:

> Even a small low-noise fan (ex-PC power supply, for example) will do 
> wonders in keeping the whole thing cool. 

Just be aware the mean time before failure (MTBF) of small fans is 
orders of magnitude smaller than most components, and considerably 
shorter than decent fans.

Most PC power supplies have fans with sleeve bearings, which generally 
have even lower MTBF's than those with ball bearings. Couple that with 
the fact the fan is used, and generally made very much to a price, I 
personally I would steer well clear of them.

AC fans normally have much longer lives, but they tend to be bigger and 
more expensive.

I have a PC here, which I bought from work for £25 or so. Two fans had 
failed - one on one of the two 450MHz CPUs, another on the hard drive 
caddy.

On my Sun workstation, two small of its 5 fans have failed on that too. 
One was on the Celeron processor of a "PC" that fits on a PCI slot of 
the Sun (a PC inside a Sun) and the other was on the DC-DC converter 
that supplies power for the CPUs (I think). The former fan I removed 
(decided it was next to useless and Celerons are dirt cheap) and the 
latter I replaced with another fan.

*Generally*, I find Sun workstations run fine for years without fan 
trouble, despite the fact they run 24/7, but fan failure on PCs seems 
very common.

-- 
Dr. David Kirkby,
G8WRB

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/