3 Apr
2012
3 Apr
'12
6:07 a.m.
All well and good. One tiny point. I worked for DEC Terminals Product Line
when those items where in current production.
The tubes were just fine without the face plate and met all implosion
requirements. Some (Green I think) did not have them at all.
However certain national safety specifications required the second screen
and its anti splinter layer. This was regardless of if the underlying tube
met the implosion spec. The spec was that it was present and its materials
met the requirements.
I think they put them on all the white ones to save having two different
cases.
I am perhaps a bit over familiar with the way I handle CRT's. However in the
time when I was a student apprentice in the 1960's I did work in a High
Voltage test lab (Anybody for a bit of 500KV?) and the guy I worked for had
been part of the original EMI television development team in the late 1930'.
Guess who got stuck with mending cranky 1950's TV's with live chassis?
"Isolation Transformer Rod? What do you want one of those for?"
I passed all of the safety tests. In those days they consisted of still
being alive when you left.
Regards
?
Rod Smallwood
?
?
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Tony Duell
Sent: 02 April 2012 20:16
To: cctalk at classiccmp.org
Subject: Re: how do you crack (open) a Rainbow mono monitor?
Whilst I do agree your safety concerns. I would say not all tubes have th=
is
arrangement and that the thin bits are at the other end. The point is the
tube is being supported as intended at the four front corners by the meta=
l
band made for that purpose.
I am sure the tension band is also part of the implosion protection, and
you are leaving that alone. However, I've seen CRT data sheets which stat
that the CRT has a 'twin panel faceplate' or soemthing similar and that
this is also part of the implosion protection system.
My view is that unless you _know_ the CRT can't implode violently even
with the outer faceplate removed, you should not leave it off.
Unfortunately, no manufacture is going to say that (even if it is true),
due to liabiltiy concerns, so I don't know how to be sure.
Having spent some time in a re-gunning facility maybe I'm just used to CR=
T's
I am not commmenting on the fact that yuou're doing things that could be
dangerous if doen incorrectly _while you are doing them_. Let me give you
an analogy. I think we all agree that 400V DC at essentially unlimited
current is lethal. And yet many of us routinely work on SMPUs that have
that sort of voltage derrived directly from the mains. I try to be
careful when I;m working on one...
But, no way would I leave a device in service with the 400V rail exposed.
It's one thing to have it l;ike that on the bench when you're the only
person around, it's quite another when other people might ocme into
contact with it. I would not have a machine 'in use' with safety covers
on the PSU remvoed or missing.
And IMHO it's the same with CRTs. If you know what yo are doing, it is
almost certainly safe to cut trhoug hthe bonding, remvoe he faceplate and
rebond it. But I feel you should end up wit hthe CRT in as safe a
condition as it was when it was made. Not with protecive parts remvoed.
-tony