Re: Monitors, Power Supplies and APANA

[Telford Tendys <telford@eng.uts.edu.au>]

> I don't want to be a worry wart, but I would be careful in repairing 
> things like power supplies and monitors without professional supervision
> If we are putting these computers into peoples house, I would be 
> concerned with the liability issues.
> Faulty power supplies and monitors have been known to cause fires.
> I don't think it would be worth the risk.

I would not expect a power supply to be able to do much damage
when it goes, especially regarding fire because the supply is in
a steel box and that steel box is in another steel box (the computer
case). They can sometimes blow in a violent manner but first the box
takes the brunt of the energy and then your fuse blows.

Some of the very old ones sometimes overvolt the motherboard if you
turn them off and on fast enough or during mains ``brown outs''.

Monitors are a more serious fire hazard because they somehow magically
attract dust and people tend to have them sitting uncovered (which you
MUST do to keep them cool) where lots of dust will enter them. The result
is that inside an old monitor is usually filthy with dust and this can
make a discharge path for high voltage, especially on humid days.

It's still a BAD idea to attempt repair on power supplies or
monitors (other than replacing fuses) because it is quite difficult to
do and quite time consuming. It also requires an oscilloscope and sometimes
a circuit diagram, depending on the fault. Getting into this sort of
repair is taking time and effort away from the main thrust of activity
for the sake of easily replacable equipment.

Work that is easy to do is to pop the back off a monitor and use a
vacuum cleaner and a dry duster to clean up the dust buildup. This
improves airflow and reduces the chance of discharge, it's fast to do
and requires no skill (just a little care). Most equipment has an
internal fuse which is socketed, these fuses are usually standard 1A, 2A,
5A etc so an identical replacement can easily be purchased.

Trying to do anything more than that is just a waste of time.
The same holds for rewiring cables, realigning disc drives,
replacing switches in mice or other similar repairs.
Completely aside from liability, if the job is more difficult than
cleaning contacts, twiddling some adjustment or something immediately
easy then it is probably better not to do it.

	- Tel