"Arfa Daily" wrote in message
...

"Jim Yanik" wrote in message
.. .
"Arfa Daily" wrote in
:


"Franc Zabkar" wrote in message
news On Thu, 15 Jun 2006 23:48:02 GMT, "Arfa Daily"
put finger to keyboard and composed:

Most shot used in clay shooting is no longer lead, I seem to recall.
Anyway,
the point is that if it is, it is not recycled, so remains lying
where it is. Solder accounts for less than 1% of the world's mined
lead, over 80% going to car battery manufacture. The car battery
industry have managed to organise virtually 100% safe recycling, so
are allowed to carry on using lead on this basis, and the contention
that there is no suitable alternative. With the coming of the WEEE
directive shortly, end of life electronic equipment will have to be
safely recycled in much the same way, so where's the difference ? If
the car battery people can do it, I'm sure that the electronic people
can also do it with less than 1/80th the volume.

I wonder how much lead is in a typical CRT? BTW, I googled for "lead
free CRT" but got very few hits.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

First to Jim two posts above. You are missing the point. The
electronic waste will no longer sit in landfill, because the new WEEE
directive, in Europe at least, will make sure that the equipment is
recycled, and any lead content removed. Electronic equipment in
landfill will soon become a thing of the past. Anyway, just how
soluble is lead in water ? I'm not too sure, but I expect some clever
chemistry graduate will tell us. In the past, water was delivered to
all households in the UK via lead pipes. In a lot of older properties,
it still is. Certainly, the house that I grew up in had lead pipework.
I am not aware of people of my generation all dying of lead poisoning,
or having suffered intelligence lowering due to lead-induced brain
damage. In fact, since lead piping has been being removed here, the
kids have been getting progressively thicker ... !! I have heard
people say that delivering water via lead pipes is of no consequence,
because the pipes quickly get an internal coating of limescale, that
insulates the water from the lead, but some areas of the country have
very soft water, with little or no calcium content, so I'm not sure
that this argument " holds water " ( ouch !! ).

Even if lead is soluble in water, I can't imagine that it is extremely
so, and I would have thought that water treatment plants would have
removed any in their raw input, or could be made to do so fairly
easily. Of much more concern, I would have thought, must be the
organic fertilizers and such that get into the water supply. I don't
know what the situation is your side of the pond ( I'm assuming you
are US based ) regarding landfill. All we ever hear over here, is that
your glorious leader is not a very eco-friendly guy, but I'm sure from
what I've seen on my frequent visits, that isn't the case amongst the
general population.

To Franc. I'm not sure what the percentage of lead is in the
lead-glass that is used for CRT faceplates, but as far as I am aware,
it's another technology that has been deemed not to have a viable
alternative, so has been granted an exemption from the RoHS directive.
Total recycling of this glass should be possible, with no
lead-to-environment contamination. As well as the faceplate glass, I
seem to recall that there is some issue also, with getting a
vacuum-proof seal between the CRT pins and the glass, that involves
possibly some other hazardous substance covered by the directive.
Interesting stuff. If anyone has any strong objections on the grounds
of this being off-topic, say so, and I'll stop raising new points ...

Arfa




I believe the lead in CRT glass does not leach out.
It's probably the monitor electronics is where the lead is coming from.
Also,it's not just the faceplate the lead-glass is used,as the lead is
intended to attenuate X-rays which I believe scatter BACK from the
target.

--
Jim Yanik
jyanik
at
kua.net

Now I come to think back to my college theory days ( blimey, that was a
long time ago ! ) I seem to recall that the x-ray emissions from a
monochrome tube are barely detectable, and those from a colour tube, only
fall into the weak and soft category, due to there only being around 25kV
available for acceleration, and that the electron beam is not streamed
directly onto a target anode. Indeed, the beam doesn't impact on a
physical anode as such, at all, but requires a DC path for the spent
electrons to return to the power supply, and that seems to ring distant
bells in the cobweb-y recesses of my brain, as being the reason that lead
doped glass is used for the faceplate ie to make it sufficiently
conductive that it forms a high impedance return path back to ground via
the rimband.

On the other hand, going back to the early days of colour television, when
a GY501 HV rectifier and a PD500 shunt stabilizer were used, these two
thermionic devices *did* produce significant x-radiation due to the
electrons impinging on a genuine tungsten anode, hence the reason that if
you were working on the HOP stage with the cage removed, you needed to put
a lead glass shield around the shunt stabilizer tube, but if you were just
working on the set in general, no such protection for your nuts from CRT
x-radiation was required. Must've worked tho' as I've got three kids ...

I also seem to recall that in order for *useful* hard x-rays to be
produced, a proper x-ray tube runs with 90kV + ??

Arfa


Those were hatefull sets to work on - I held onto my day job until the
setmakers started to introduce designs with (non shunt) regulated EHT!