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