On Nov 1, 1:53*pm, Peter Parry wrote:
On Sun, 1 Nov 2009 02:16:32 -0800 (PST), NT
wrote:

On Nov 1, 9:39*am, Peter Parry wrote:
I haven't come across too many domestic microwave ovens operating in
hostile environments (unless of course you count children as a hostile
environment) but that is why *MIL-HDBK-217F is so much more useful
than data sheets as it models such excursions from the norm. *Using
the ground mobile model - the microwave in a cross country vehicle
used cross country - the reliability does, as you say, drop. *The MTBF
goes down to merely 4,000,000 hours

Do you think all chinese manufacturers adhere to such standards at all
times?

It isn't a manufacturing standard but a method of predicting failure.

every such assessment is based on certain specs or characteristics of
the component under assessment. Why you assume all manufactured leak
resistors conform to it I dont know. It does seem rather optimistic.


More importantly, we have 65 million people in the UK and IIRC around
20 million households. So say around 20 million domestic microwaves.
Each one of those is plugged in 8760 hours per year. Now, how many
discharge resistor failures would you expect to see per year in the UK
in domestic microwaves using your figures?

Now I know for sure you don't understand probability and risk. *Almost
every week in the UK someone wins a multi-million pound prize in the
lottery. *Almost every week in the UK more than one person dies, often
unexpectedly, while going to buy a ticket to enable them to win that
prize.

Should we ban the National Lottery on the grounds it kills so many
people?

Straw man.


Assume your figure of 20million microwaves is correct. *The hours on
figure of 8760 is completely irrelevant as the capacitor is only
energised when the oven is cooking, a averaged figure of about 100
hours is probably more realistic but let's be real pessimists and say
each and every oven operates for 1 hour a day so about 400 hours per
year. *A total of 8,000,000,000 per year

In the UK it is quite likely a dozen or so microwave ovens have faulty
drain resistors. *Let's be real pessimist though and assume 100.

8 billion over 4 million = 2,000. I forget the other figure you had,
but it still assumes all drain Rs are to spec, which for chinese mfred
goods is a bit optimistic.


*That
gives a one in 200,000 chance of your oven having this particular
fault.

Let's further make the extraordinarily improbable assumption that
working on such an oven will invariably be fatal so that 1 in 200,000
is your chance of death. *

but youre still making assumptions I simply dont believe are valid.
And the conclusions you reach just dont tally with real life
experience.


Compare that with the chances of you dying in a road accident of about
1 in 17,000 or the chances of death in pregnancy of about 1 in 8,200.
I wonder how many husbands mention to their wives that pregnancy is
nearly 25 times more lethal than repairing a microwave oven without
precautions?

The reason the death rate from microwave oven repairs is zero is
because the chances of one happening are very remote. *

1. Could that be because so few people are unwise eough to repair them
without discharging the cap

Nope.

2. This kind of foolishness would be found outside of insustry rather
than in it.

You obviously have little experience of industry.

sigh


3. Amulance and fire brigade aren't always called for a dead person.

I'm not aware of any instance where people lying dead on the floor by
the side of a smoking microwave have simply been placed in a relatives
car and delivered to the undertaker for burial but any sudden and
unexpected death requires a coroners inquest. *The results of inquests
also went to the HSE.

And I'm sure that all polish, african etc workers here follow all laws
to the letter. And involve the authorities when its the last thing
they need.

You're trying to asses this, but just making too many assumptions.

And even if we went with your figure, its still dumb to not put a
screwdriver across the terminals first. 4 seconds of trivial action to
avoid the risk of death.


NT