F
Franc Zabkar
My PC is located within two metres of my TV set. With covers off, I
see vertical "banding" interference on one particular UHF channel.
This interference disappears when I turn off the PC.
- Franc Zabkar
My PC is located within two metres of my TV set. With covers off, I
see vertical "banding" interference on one particular UHF channel.
This interference disappears when I turn off the PC.
- Franc Zabkar
K
kony
I"ve seen plenty too, with almost any newer system. Seem to
be more a matter of whether the user has susceptible
equipment nearby rather than whether there is _potential_
for interference.
S
scharf.steven
DaveW said:
There is no requirement for a metal case. If you could pass FCC class
B, you could make it out of cardboard.
A common method of shielding plastic cases is to spray them with
conductive paint.
That said, it is quite difficult to pass FCC with a plastic case, but I
have done it. It was no cheaper that using a steel case, after all the
stuff we had to do in order to get it to pass.
S
scharf.steven
Mxsmanic said:
It would not keep it cooler. A closed case allows forced air to be
drawn in the front and expelled out the rear, with positive pressure in
the case.
It's very common in a lab environment to have things open. But we
usually have to have fans blowing on the system.
Mesh wil solve the EMI problem, not that anyone that's building a
home-made systems worries about it much.
The full tower cases are fine for this, but they are not that common
anymore because people want cases that fit into their existing
furniture.
I recently made a system for my son with an Antec SX-1040
(http://www.antec.com/us/productDetails.php?ProdID=81046) precisely
because I wanted a case with plenty of space, and good cooling. It has
excellent cooling, using four 80mm fans, in addition to the power
supply cans. I had to add some cooling fans to the desk, otherwise the
heat just built up in the space for the tower, though the fans only
took 5 degrees off the interior temperature, and 3 degrees of the CPU
temp.
The SuperMicro SC762 is even larger
(http://www.supermicro.com/products/chassis/tower/?chs=760).
But a lot of people are interested in stylish cases, rather than more
functional ones.
Ooh, I want some of those powerful silent fans!
K
kony
Yep, metal paint ain't cheap, it's often done with metal
sheeting attached to the plastic when possible.
D
David Maynard
kony said:
Yes. I've got an old 486 system made by Compudyne, I think it is, and it's
a plastic case with metal sheets all over the place inside for EMI shielding.
Looks like a case, pun, of 'engineering' gone amok as it's loaded with
'clever ideas' that seem to univerally make things more of a nightmare than
'better'. Not the least of which being that half of it is structurally
plastic, necessitating the myriad of attached metal panels (cost),
resulting in a case that resembles a half cooked flippy floppy hinged
noodle when opened and that prefers any orientation other than properly
aligned when you try to close it.
It 'works', though, and you can tell that an incredible amount of
engineering and design effort went into the thing. It's just that a plain
metal box would have been infintely superior from just about any standpoint.
T
ToolPackinMama
David said:
LOL! BTDT.
B
bhoover
David said:
Interesting though. This may seem bizarre, and I kind of like the idea
of an "open air" computer, so not to knock it, but hell, you could put a
computer in just about anything. For instance, nature worshipers could
go au natural, put their hardware in an old dried up tree hole or
something. Prolly take some serious discipline, and violent cleaning to
turn it around, into something half way decent, and hospitible though.
I know. Way off topic. But still..
http://www.hypography.com/article.cfm?id=34241
Study probes ecosystem of tree holes
Web posted Jun 16 2004 @ 02:09 by Tormod Guldvog
If you think your place is a dump, try living in a tree hole: a dark
flooded crevice with years of accumulated decomposing leaves and bugs,
infested with bacteria, other microbes, and crawling with insect larvae.
"It's a war inside a tree hole"A biologist at Washington University in
St. Louis has studied the ecosystem of the tree hole and the impact that
three factors ? predation, resources and disturbance - have on species
diversity.
<> Jamie Kneitel, Ph.D., Washington University in St. Louis post
doctoral researcher in biology in Arts & Sciences, and Jonathan Chase,
Ph.D.,Washington University assistant professor of biology, found that
tinkering with any of those factors changes the make up of the
community.
Kneitel uses the Richard the III reference - "subtle, sly and bloody,"
Richard III's mother's description of her son as a little boy - when
talking about the ecosystem he studies. A tree hole can be found in
nearly every forest and is an ecosystem surprisingly overlooked by
ecologists.
Created by a lost tree branch or deformed trunk, the tree hole collects
water, which supports an aquatic community that lets an ecologist like
Kneitel address fundamental ecological questions. In this small
ecosystem, bugs and leaves fall into this pool of water and decompose
which provides the energy for hundreds of species, including bacteria,
protozoa, and mosquito larvae. It's a generally thriving community where
these critters battle each other in a mini-survival-of-the-fittest.
To perform his study, Kneitel recreated the tree hole ecosystem in the
laboratory, which allowed him to change the parameters to create
different ecological situations. The most common disturbance for a tree
hole is lack of water. Resources equate to the food supply, and
predation among the three basic organisms - protozoans, rotifers and
mosquito larvae - is rampant, and varies depending on resources and
disturbance.
"Predators, resources, and disturbances are the most common factors that
affect communities, but few studies look at all these factors together"
Kneitel said. "Not surprisingly, predators, resources, and disturbances
all had really strong effects, but the interesting finding was how these
various factors interacted. Community composition was altered by all
treatments, depending on which treatments were present.
Certain species were associated with each of the treatments - those in
predator treatments were those tolerant of predators, those in
disturbance treatments were tolerant of disturbances, and so on."
Kneitel studied between 20 and 25 protozoan species and four rotifers;
protozoans are single-celled organisms, rotifers, multi-celled, yet some
protozoans are bigger than rotifers and will prey upon them. Mosquito
larvae browse and filter-feed and will attack either of the groups of
species.
'It's war inside a tree hole," Kneitel said. "We found that predation
has the strongest effect when there are no disturbances. Disturbance has
the strongest effect when there is little predation. When there is no
disturbance or predation, competition is the primary source of
extinction. A disturbance - a dry tree hole - pretty much kills
everything but certain protozoans that can go dormant and survive the
cycle."
The results will be published in a forthcoming issue of Ecology. The
work was supported by NSF. Kneitel said most studies of this sort look
at two factors, compared with the three he and Chase studied.
"Our results show that if you change any one of the three factors, you
alter the face of the community," Kneitel said. "We found that we had a
group of species that were good competitors, another that is good at
tolerating predators, and yet another that can survive and tolerate
disturbances.
"These traits (niche) differences allow many species to coexist with one
another at different spatial scales. This is true for this community,
but also many other communities work in this way."
Kneitel said the scale of the tree hole system allows him to ask "big
picture" questions of ecosystems that can't be asked on a large scale.
"You can't really ask these types of questions using long-lived
organisms like wolf and deer populations," he said. "It takes years and
years to see the effects of predation and disturbance on population
dynamics. With these communities, you can do an experiment in a month."
The source of this story is Washinton University in St. Louis.
S
scharf.steven
That plastic case is from Palo Alto Design Group, if it's the big
squarish desktop case I'm thinking of. I did the Compudyne
motherboard/case combinations for CompUSA when I was product manager
for the U.S. office of a very large Taiwanese motherboard company,
many years ago.
It involved every CompUSA store becoming a UL certified "factory,"
since the systems were assembled in the store, plus we had to get FCC
class B for them, for every motherboard/case combination, with a worst
case set of add-on cards.
One day I got a call from a CompUSA, stating that a UL inspector was at
the store, and that he found non-UL approved lithium batteries in the
systems. Some braniac in Taiwan had decided to save money by having
"housewives assemble batteries into plastic cases." We had to take back
thousands of these batteries, and sell them to customers that didn't
care about UL.
squarish desktop case I'm thinking of. I did the Compudyne
motherboard/case combinations for CompUSA when I was product manager
for the U.S. office of a very large Taiwanese motherboard company,
many years ago.
It involved every CompUSA store becoming a UL certified "factory,"
since the systems were assembled in the store, plus we had to get FCC
class B for them, for every motherboard/case combination, with a worst
case set of add-on cards.
One day I got a call from a CompUSA, stating that a UL inspector was at
the store, and that he found non-UL approved lithium batteries in the
systems. Some braniac in Taiwan had decided to save money by having
"housewives assemble batteries into plastic cases." We had to take back
thousands of these batteries, and sell them to customers that didn't
care about UL.
D
David Maynard
ToolPackinMama said:David Maynard wrote:
LOL! BTDT.
Hehe. We all (meaning engineers) have. It's natural to seek the most
complex solution to a trivial problem because, frankly, the easy one isn't
'fun' and doesn't use the latest toys
M
Mxsmanic
David said:
The accountants probably told the engineers that a plastic case was
mandatory for cost reasons, and then ignored the engineers when they
explained all the additional work that would be required to make the
case compliant.
D
David Maynard
Could be. It's a tower that looks like, from the upside down arrangement
with 5 1/4 inch bays on the bottom, they intended it to sit on a desk top.
That might explain the clamshell idea because, as I looked at it, I got the
definite impression someone had 'easy to assemble' and 'easy to debug' as
an intended goal.
It's well made inside. It's neat, routed and cable tied with a place for
everything, everything is in it's place, and precisely the right length.
Oh man. I've been through those 'inconsequential change' things too.
D
David Maynard
Mxsmanic said:
Well, accountants do some strange things from time to time but specifying
hardware design isn't usually one of them. Their approach is generally much
simpler, such as explaining you have a 1 lb budget for a 10 lb box and the
rest is your problem.
Manufacturing then tells you they ain't got tools to make 10 lb boxes, R&D
tells you it's not technologically possible to make 10 lb boxes, marketing
says 10 lbs ain't big enough because the competition has 12 lb boxes, with
bells, the buyer says lead time for the one indispensable part with no
substitute is 200 years but contract admin has forbidden purchasing from
them anyway, Q&A suddenly announces a new standard requiring 10 lb boxes
survive a nuclear blast with the mega-tonnage TBD, which generally means
some time significantly after your scheduled delivery, and the board
doesn't know what a 'lb' is but wants the arbitrary schedule you couldn't
make to begin with cut in half.
None of which you can find in the conceptual drawings, statement of work,
or specifications for the 5 lb box you were asked to design.
Other than that it's a piece of cake
S
scharf.steven
They were very easy systems to assemble, because the case was big and
open. IIRC, the motherboard in the 486 based system used a UMC chipset,
and a separate card for the SuperIO functions (serial/parallel/game
port).
open. IIRC, the motherboard in the 486 based system used a UMC chipset,
and a separate card for the SuperIO functions (serial/parallel/game
port).
S
scharf.steven
There have been instances of all of those types of PCs. They fail
because while everyone says how great they would be, no one wants to
pay a big premium. Adding interconnect cables, separate power supplies,
etc, adds cost. I.e., you used to be able to buy a PC with the CD-ROM
and floppy drives in a separate desktop cabinet, since there was no
need for the whole PC to be easily accessible. But this involved two
cases, two power supplies, a host of cables, etc.
The trend now is to not have a gazillion pieces strewn around the room,
connected by cables. So stuff like integral media readers, removable
drive bays, etc., are becoming more common.
One way to achieve what you want is to set up a client-server
environment, with a separate server. But thin clients have
traditionally been rather low performance, and not cheap because they
require specialized thermal solutions, and low power processors (10
watts or so) to be able to be silent and to fit into small cases.
I worked on one high performance thin client at my last job, and the
demand was very high (we could not manufacture components fast enough
for the customer). When I go to my local library, and use their
extremely slow thin clients, it makes me wish that they would buy the
higher performance machines, but they were very expensive (as well as
being fanless).
because while everyone says how great they would be, no one wants to
pay a big premium. Adding interconnect cables, separate power supplies,
etc, adds cost. I.e., you used to be able to buy a PC with the CD-ROM
and floppy drives in a separate desktop cabinet, since there was no
need for the whole PC to be easily accessible. But this involved two
cases, two power supplies, a host of cables, etc.
The trend now is to not have a gazillion pieces strewn around the room,
connected by cables. So stuff like integral media readers, removable
drive bays, etc., are becoming more common.
One way to achieve what you want is to set up a client-server
environment, with a separate server. But thin clients have
traditionally been rather low performance, and not cheap because they
require specialized thermal solutions, and low power processors (10
watts or so) to be able to be silent and to fit into small cases.
I worked on one high performance thin client at my last job, and the
demand was very high (we could not manufacture components fast enough
for the customer). When I go to my local library, and use their
extremely slow thin clients, it makes me wish that they would buy the
higher performance machines, but they were very expensive (as well as
being fanless).
B
Bob Adkins
Did you ever see an old Kaypro "portable" case? Now THAT was some
"engineering"!
It was an ancient precursor to the laptop. It was huge, with built-in ~9"
CRT, all made from heavy gage aluminum, all aircraft-looking rivnuts and
fasteners. Weighed about 30 pounds. Just the case must have cost more than a
modern computer. I tore one down and salvaged the aluminum sheet metal,
brackets, heavy fiberglass braces, rivnuts, and high quality SS fasteners. I
still use the aluminum for building home made brackets and trays.
Found a nice picture of it here: http://oldcomputers.net/kayproii.html
Even the keyboard was mounted in a heavy gage aluminum tray, which I use for
a shelf in my shop.
K
kony
Did you ever see an old Kaypro "portable" case? Now THAT was some
"engineering"!
It was an ancient precursor to the laptop. It was huge, with built-in ~9"
CRT, all made from heavy gage aluminum, all aircraft-looking rivnuts and
fasteners. Weighed about 30 pounds. Just the case must have cost more than a
modern computer. I tore one down and salvaged the aluminum sheet metal,
brackets, heavy fiberglass braces, rivnuts, and high quality SS fasteners. I
still use the aluminum for building home made brackets and trays.
Found a nice picture of it here: http://oldcomputers.net/kayproii.html
Even the keyboard was mounted in a heavy gage aluminum tray, which I use for
a shelf in my shop.
Wasn't it working? That might've been worth some $$$$ to a
collector, certainly more than the cost of that much sheet
metal if you merely needed materials.
M
Mxsmanic
Bob said:Did you ever see an old Kaypro "portable" case? Now THAT was some
"engineering"!
It was an ancient precursor to the laptop. It was huge, with built-in ~9"
CRT, all made from heavy gage aluminum, all aircraft-looking rivnuts and
fasteners. Weighed about 30 pounds. Just the case must have cost more than a
modern computer. I tore one down and salvaged the aluminum sheet metal,
brackets, heavy fiberglass braces, rivnuts, and high quality SS fasteners. I
still use the aluminum for building home made brackets and trays.
Found a nice picture of it here: http://oldcomputers.net/kayproii.html
Even the keyboard was mounted in a heavy gage aluminum tray, which I use for
a shelf in my shop.
It's interesting to note that the main reason these first portable
computers were so bulky and heavy was that they had to contain large
diskette drives and a CRT. Remove the floppies and the CRT and they'd
nearly fit into a modern laptop. The development of inexpensive,
high-quality, reliable hard disk drives and flat-panel screens is what
made laptops really practical; unfortunately, that didn't happen until
many years after the PC itself was invented.
I remember seeing people lugging those large Osbornes and what-not
around occasionally and thinking that they didn't seem very practical.
However, I did like the old IBM 5100 from a style standpoint, although
it was twice as heavy as the Osbornes and had less horsepower. It had
a nice cartridge tape drive, which I found superior to floppy disks,
and the fit and finish were excellent.
D
David Maynard
Bob said:
Sure, I remember them. And the Osborne. And, of course, making 'portables'
is how Compaq got started.
It's certainly engineered but not in the same way as the Compudyne case I
was talking about. The Kaypro is primarily bend sheet metal, a simpler and
less costly solution than making molds with the attached shielding bits.
B
Bob Adkins
I was in awe of the HDD. It was a 5mb unit, and was very large and heavy. I
should have kept it.