sci.electronics.repair@googlegroups.com

Today's topics:

* Running a PC outside of a computer case - 4 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/767389e3dda5bc79?hl=en
* Recommendation for electronics forums? - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/a2a97ca7806d8277?hl=en
* hello - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/9035e7f08583f66f?hl=en
* USB device interfering AM radio - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/3ab7201fcff1b0c6?hl=en

==============================================================================
TOPIC: Running a PC outside of a computer case
http://groups.google.com/group/sci.electronics.repair/t/767389e3dda5bc79?hl=en
==============================================================================

== 1 of 4 ==
Date: Sun, Mar 20 2011 7:23 pm
From: D

On 3/20/2011 5:30 PM, David Nebenzahl wrote:
> On 3/20/2011 3:15 PM D spake thus:
>
>> Thanks for the replies. I only have one ATX case, which currently
>> contains my working computer, which I want to have available until I
>> get the new bits checked out, OS loaded, up and running, etc. I have a
>> momentary contact switch from an older machine which should do nicely
>> for powering up, although I've heard of people simply using a small
>> screwdriver for this. I'd rather not run the risk of accidentally
>> shorting to the wrong terminals, though. Agreed care is in order,
>> probably don't want to have my pitcher of Koolaid on the same table as
>> the spread-out bits, but I think it should be OK.
>>
>> I gather then that there's no need to ground the PSU case & other bits
>> together with clip leads?
>
> No, the case isn't required as a ground. All needed grounds are already
> in the connection betwixt PSU and motherboard.
>
> Of course, you won't have an FCC-compliant setup without the case, RF
> emission-wise, but no need to sweat that so long as you don't plan on
> running the "naked" setup more than a short time.
>
>

Hadn't considered the RF emissions. If that pitcher of Koolaid I
mentioned starts to boil (or my garage door keeps going up and down),
I'll now something's up! ;-)

Thanks again everyone for the helpful replies.

Dan

== 2 of 4 ==
Date: Sun, Mar 20 2011 7:38 pm
From: Grant

On Sun, 20 Mar 2011 14:54:26 -0700, D <none@hotmail.com> wrote:

>I've built one computer, and will soon be building another. I would
>like to initially set up & test this new machine on the bench, outside
>of a computer case (simply connecting the PSU, etc., w/o all the bits
>being in a case). Seems straightforward, but I have a couple questions.
> First, am I correct that the front panel on/off switch generally used
>to start the PC is simply a momentary contact switch that briefly
>connects the "PW+" and "PW-" terminals on the MOBO? Same with the
>reset/reboot switch function, using "res+" and "RES-"? Also, is it
>necessary to run a ground wire between the PSU case, and one of the MOBO
>pads where the screws go to attach the MOBO to the case when installed?
> Since the metal case would "ground" these 2 together, I was wondering.
> If this is required, should all metal cases (HDD, DVD drive, etc) be
>so "grounded together"?
>
>Any other helpful points about running a PC on the bench this way would
>be greatly appreciated.

I do temporary lashups like that to test gear, need to put the mobo on a
book or something non-conducting to raise the edge where NIC and display
cards go. Don't need extra grounds. The power is momentary contact, low
voltage, shorting out the connectors in that area shouldn't do a damage as
they're either switch inputs or current limited LED outputs.

Put the hard drive where you wont bump it, probably on top of the optical
drive. When in doubt, sticky tape stuff down. You want LEDs in the power
and HD positions to get an idea what's happening. Speaker too, for the
beeps. Pair of momentary switches or wires for power and reset... I keep
an old switch + LED harness from a discarded case around for controlling a
bare mobo.

Grant.
>
>TIA
>
>Dan

== 3 of 4 ==
Date: Sun, Mar 20 2011 9:31 pm
From: stratus46@yahoo.com

On Mar 20, 2:54 pm, D <n...@hotmail.com> wrote:
> I've built one computer, and will soon be building another.  I
would
> like to initially set up & test this new machine on the bench,
outside
> of a computer case (simply connecting the PSU, etc., w/o all the
bits
> being in a case).  Seems straightforward, but I have a couple
questions.
>   First, am I correct that the front panel on/off switch generally
used
> to start the PC is simply a momentary contact switch that briefly
> connects the "PW+" and "PW-" terminals on the MOBO?  Same with the
> reset/reboot switch function, using "res+" and "RES-"?  Also, is it
> necessary to run a ground wire between the PSU case, and one of the
MOBO
> pads where the screws go to attach the MOBO to the case when
installed?
>   Since the metal case would "ground" these 2 together, I was
wondering.
>   If this is required, should all metal cases (HDD, DVD drive, etc)
be
> so "grounded together"?
>
> Any other helpful points about running a PC on the bench this way
would
> be greatly appreciated.
>
> TIA
>
> Dan

I've built a few dozen PCs over the years. I would never bother
running the system out of the case. Mine nearly always work fine ( one
exception ) and then you'll have to unplug and mount it anyway and
plug together again. You're more likely to screw it up OUT of the case
so why take the chance and waste the time? BTW the case / power supply
I'm using now - the wife's machine - is on its 4th motherboard. The
latest change 2 weeks back took an hour - so short because the old and
new boards are nearly identical and didn't require any re-installation
of the software. The newer board can use the higher power/speed Phenom
II processor now in it.

G²

== 4 of 4 ==
Date: Mon, Mar 21 2011 1:02 am
From: D

On 3/20/2011 9:31 PM, stratus46@yahoo.com wrote:

>
> I've built a few dozen PCs over the years. I would never bother
> running the system out of the case. Mine nearly always work fine ( one
> exception ) and then you'll have to unplug and mount it anyway and
> plug together again. You're more likely to screw it up OUT of the case
> so why take the chance and waste the time? BTW the case / power supply
> I'm using now - the wife's machine - is on its 4th motherboard. The
> latest change 2 weeks back took an hour - so short because the old and
> new boards are nearly identical and didn't require any re-installation
> of the software. The newer board can use the higher power/speed Phenom
> II processor now in it.
>
> G²

I rely quite heavily on my PC on a daily basis, and don't really want to
be without a functional machine. In order to load the OS & see if
everything is operable, I only need to connect 1 HDD, 1 DVD drive, the
vid card & monitor, keyboard, mouse & PSU. The only bit I'll need from
the existing machine is the vid card, an easy R&R in either direction.
No big deal, and if there is a problem, a DOA component, perhaps, it's a
lot less trouble finding out this way and dealing with getting a
replacement than removing the new board & completely reassembling my
working unit so I have it in the meantime.

==============================================================================
TOPIC: Recommendation for electronics forums?
http://groups.google.com/group/sci.electronics.repair/t/a2a97ca7806d8277?hl=en
==============================================================================

== 1 of 2 ==
Date: Sun, Mar 20 2011 7:39 pm
From: D Yuniskis

Hi Jeff,

On 3/20/2011 4:11 PM, Jeff Liebermann wrote:

[attributions elided]

>> But, illustrates the point, well. Yet, doesn't say how accessible
>> those "4" are nor where their interests lie.
>
> Actually, very accessible, if they're interested. We have a local

-----------------------------^^^^^^^^^^^^^^^^^^^^^

I seem to recall making comments to that effect ;-)

> startup, Elecraft, that makes ham radio kits and accessories. Most of
> the qualified hams in the area are now working for them.
> <http://www.elecraft.com>
> There's not much design work being done locally, but the engineers and
> techs certainly know how the radios operate.
>
>> E.g., you would be
>> hard-pressed to get me to help you design an audio amp out of
>> discretes -- but, could probably keep me obsessed with trying to
>> cut power consumption by half a milliwatt on a battery powered
>> device! (and I'm a *helpful* soul ;-)
>
> I have a similar problem. When I was still designing electronics, the
> major obsession was reducing the cost. At that time, it meant
> reducing the component count. If you get my attention, I can waste
> enormous amounts of time, on futile exercises in component count
> reduction. Same with unusual ways to implement simple things.

In the mid 70's, I had to design a replacement "front panel"
for a Nova (2 or 3... I can't recall) minicomputer. This is
the vintage equipment where you "bit-switched" (toggled) data
into memory (real core!), forced a value into the program counter
and then hit "run".

The actual front panel was bulky -- all those "bats" on the front
panel switches plus plastic molding, etc. Since the machine
only had to do certain very fixed things (I guess it qualified as
an "embedded system" -- even though the processor was the size
of a small washing machine!), it was silly to ship the bulky
panel with the unit.

The panel worked by driving values onto an "open collector" bus
and stroking control lines. So, any replacement "front panel"
needed logic to interface to a few dedicated switches (reset,
IPL, etc.), decode logic to drive the right values onto the
bus, some crude timing (remember, we are emulating things that
a human being does "by hand") and, of course, open collector
drivers to actually *drive* the bus.

I ended up with a design that used a 7 segment decoder (!)
wired in a bizarre way to (coincidentally) get the right
values onto the bus based on an examination of the switch
states connected to the BCD inputs thereof. (this predates
FPGAs, GALs and even *PLAs*!)

My boss was impressed -- but too scared to risk such a bizarre
implementation: "How will anyone ever know how it is *supposed*
to work?" (to me, that was pretty obvious: the devices work
just like any other devices... read the data sheet!)

>> A lot also depends on how dense that population of "experts" is,
>> as well. E.g., our county is 9,200 sq mi with a population of just
>> over 1,000,000. So, 90 people / sq mile. *If* we have those 2800
>> hams, here (no idea), that would be one ham for every 4 sq mi. That
>> can make accessing that "expert" a bit problematic (I find learning
>> is usually faster "in person").
>
> You can get a fair idea of the number of hams by diving into the FCC
> ULS database and searching for counts by your local zip codes.
> <http://wireless2.fcc.gov/UlsApp/UlsSearch/searchAmateur.jsp>
> For 95005 (Ben Lomond, CA), it shows 61 licenses. Unfortunately, the
> FCC updates the data perhaps every 10 years, so some hams that have
> moved out or died are still listed.

Lots of ZIP codes in 9000 square miles. I'll leave that as an
exercise for the student...

>> And, if the hams (and population, in general) are not evenly
>> distributed throughout the county, it only gets worse (potentially).
>
> Worse, most hams seem to live in post office boxes.

Yes. Though, if you're smart, you use a non-USPS "p.o.box"

>> E.g., there are *no* electronic suppliers, here, within driving
>> distance. The closest possible (overpriced) retailer is clear across
>> town (and would never have the types of components that I am
>> interested in).
>
> We have one local supplier (other than Radio Shock). They're
> expensive, but not outrageous.
> <http://www.santacruzelectronics.com>

I bought some small lytic's for ~$2/ea. C'mon, now... (then
they complain when folks buy mail-order from firms out-of-state!)

>>> This is the age of specialization.
>>
>> Exactly! The days of being able to keep a drawer full of transistors,
>> diodes, resistors, etc. and hack together an amplifier -- or a logic
>> gate (!) -- are long behind us.
>
> Yep. Just finding the part in my mess is difficult. However, I do
> have a fairly good collection of 1980's vintage discrete parts, which
> are useful for raising the dead and repairing the antiques.

I find more use for *hardware* (screws, connectors, etc.) than
"components". As I get older, time is more valuable to me than
"mundane cost saving experiences" (though I replaced a power
cord on a make-up mirror, yesterday... can you spell "mindless"?).
So, if anything "complex" dies, I typically just recycle it and
replace it (I collect "spares" of lots of things so this often
just means taking another off the shelf). To invest any serious
amount of time, it either has to be a really interesting problem
*or* something of considerable value (including "irreplaceable")

> One problem with specialization is that it tends to create some rather
> bizarre implementations. I once reverse engineered a microprocessor
> design that could have been replaced by a quad op amp.

I had a colleague design a state machine for an LCD controller
using a 64KB EPROM (back when a 64K EPROM was *big*!). When I
dumped the EPROM, I discovered it implemented a simple logic
function of *3* variables (despite all the "inputs" that
were wired to it's address lines). I.e., it could have been
replaced by a quad _______ or, perhaps, a dual AOI.

<shrug> He didn't care. On to the next design...

>> Sure, you can still do it, but there
>> is no point. I can recall building 8 digit counters out of discretes
>> with nixie displays... would I bother wasting my time on that *now*??
>> (though I *have* been sorely tempted to build a Difference Engine).
>
> Hint: I never build or design anything that I can't sell or turn into
> a sellable product. When I do build something for myself, I usually
> build 3 to 5 extras, to sell to friends and recover my expenses.
> Expertise in PCB layout is a must.

I tend to take the *opposite* approach. I like building "one of
a kind" pieces. Especially as gifts. I.e., the value of the
gift is the fact that it is unique. And, sufficiently expensive
to undertake "duplication" that it would need to have a significant
number of "buyers" to make it worthwhile (i.e., it is not
economically feasible for a "competitor" to make something like
this, thereby rendering the uniqueness of the gift meaningless).

Difference Engine would be cool as it would require lots of
*mechanical* skill/assembly/fabrication -- not something you
could just run off a set of Gerbers!

Anything that I design lately that would appeal to others
I just release as "open source" (hardware and software) so
anyone who wants to invest the time/energy can copy at will.

> Note that it's still possible to have fun with electronics:
> "How to blow up a microwave"
> <http://www.youtube.com/watch?v=V9Gn0auLFUA>

I've thought about setting up a tesla coil proximate to
the hummingbird feeder to zap the *woodpeckers* when they
try to use it. But, it would be hard to control where
the discharge went... :<

(I wonder what burnt woodpecker smells like?)

== 2 of 2 ==
Date: Sun, Mar 20 2011 9:29 pm
From: "Michael A. Terrell"

David Nebenzahl wrote:
>
> On 3/20/2011 1:10 AM Michael A. Terrell spake thus:
>
> > David Nebenzahl wrote:
> >
> >> I'm looking for an online electronics forum (web-based) where I can post
> >> some questions.
> >>
> >> Don't get me wrong: I love, and usually prefer, Usenet. But I'm trying
> >> to educate myself here, am working on a project, and a web forum that
> >> allows one to post pictures would be better for my purposes. At least
> >> I'd like to try it. (The subject of my current research is the ins and
> >> outs of op amps.)
> >
> > news:sci.electronics.basics or news:sci.electronics.design are both
> > good. You get more hand holding in the .basic group, but you see the
> > same people from the .design group. They have more patience on the
> > .basic group which is intended to teach electronics, while the .design
> > group is to trade ideas between professional designers.
>
> How did you miss that I specifically requested an online forum, not
> other Usenet newsgroups? It's right up there in the very first sentence
> I wrote, for chrissakes.

My suggestion still stands. Online forums drop like flies, so I've
stopped even trying to find one that's useful. Do whatever you like.

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

==============================================================================
TOPIC: hello
http://groups.google.com/group/sci.electronics.repair/t/9035e7f08583f66f?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Mar 20 2011 8:54 pm
From: jaya kala

http://123maza.com/75/latest149

==============================================================================
TOPIC: USB device interfering AM radio
http://groups.google.com/group/sci.electronics.repair/t/3ab7201fcff1b0c6?hl=en
==============================================================================

== 1 of 1 ==
Date: Mon, Mar 21 2011 12:09 am
From: Man-wai Chang

> My guess(tm) is that you have both the USB power adapter
> and the radio plugged into the same outlet or power strip.
> Conducted radiation, through the power lines is another
> component of the problem. Your radio may be susceptible
> to junk pickup from the power lines, or for really cheap
> junk, use the power cord as an antenna.
> Clamp on ferrite beads (more like ferrite blocks) are
> available to block conducted radiation and pickup.

> A switch to non-switch mode supply would cure your problem.

Thank you both

--
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/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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^ ^ 15:07:01 up 2 days 18:41 0 users load average: 1.12 1.12 1.13
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
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