Re: Stopping RFI from a PC
First, let me note that I am in a community where electronic supplies are
not readily available--6K people in the Sierra foothills miles and miles
from Sacramento. I'm 60 miles from the nearest really full scale vendor, and
45 miles from a good used electronic parts store. While you wer complaining
that I wasn't following pdelete's dictum, I was trying to find a reasonable
coil to put around the the AC cord per other suggestions. None were readily
availble. Hence, it the intervening time I certainly felt that is worth
pursuing other avenues in this thread.
Second, pdelete asked if the unit had PFC, so not knowing I tried to contact
the vendor. The answer is now known as "No". Only their units distributed to
Europe have them I am told. Further, I talked to the vendor on the phone
finally, they have no spec sheets or circuit diagrams to distribute. What
one sees on the box is it.
Third, I decided to pull the new supply and put in the old one to find out
if my observation was correct. Yes, the old unit did not produce any RFI. I
then decided to turn on another computer in the room. It did not produce any
noise in the AM radio I was using to test interference. I then plugged that
computer into the outlet for the other 'noisy' computer. Voilla. Noise galore.
Finally, this prompted to look for other noise sources in the three rooms of
the building and examine the ground on outlet just mentioned. Since I had no
clue as to how the four circuits in the small building worked, I mapped all
the outlets, switches, and lights to the circuit breaker panel. Then I began
experimeinting by turning parts of the circuit on and off, etc. The best I
could do using this approach (so far) is to note that the one circuit that
has the most devices on it is fairly noisy. I found one device, a network
hub, that was a bit noisier than anything else.
Where I plan to go from here is likely to see if I can just plain quell the
noise at the questionable outlet and devices plugged into it. Beyond that,
I'll live with the ruckus caused on the AM portion of the dial that distrubs
me the most. In the meantime, I'm close to being off this little project,
and getting onto other things of higher priority. The obvious disturbance in
the AM signal attracted me enough to put this much time in on it, but not
enough to keep me going for days trying to squelch it. Other things first.
When they are out of the way, I'll look into this further. Summing it up I
seem to have an RFI problem of unknown origin.
As far as the new PSU unit is concerned, I'm keeping it. At least, it
doesn't just belly up every 3-4 days.
Since you are curious about this, I'll try to do you the favor of
photographing the inside of both PSUs and posting it. That's not likely to
happen today.
If nothing else, at least I now have the circuit panel mapped. Thanks for
your interest.
w_tom wrote:
If manufacturer and vendor did not provide numeric specs up
front and in writing when you bought the supply, then neither
will. Appreciate why so many power supplies are selling at
less retail price and at greater profit. They are marketing to
MBA types who somehow are experts and therefore do not ask for
numerical specs BEFORE making a purchase. As long as those
functions are not in writing, then problems are all upon you.
Why then would they even want to waste time providing
specs? They have your money which is the only purpose of
selling power supplies missing essential functions. Should
you return it, then you may only get credit towards further
purchases (maybe after a restocking charge) assuming they are
willing to accept returns on electronics. Either way, they
still have your money. Next year they may be selling this
supply under a different name.
Let's apply your technical reasoning to another homeowner.
His lights worked just fine. Therefore house electricity was
completely OK. Except that his house electricity was wired
completely wrong. Fortunately the resulting gas meter
explosion occurred when he was not home. Just because a
computer appears to work fine means the new power supply is
OK? Nonsense. The new supply was creating RFI from day one.
Therefore it was always defective. You are using the same
flawed logic of that homeowner. You assume one can 'test' for
quality which even students of W E Deming generations ago
understood to be false.
Why did the previous supply become erratic? We don't even
know that supply was problematic. For all we know, system was
fixed by breaking and remaking connections which cleans
contact corrosion. Why, with numbers, was the old supply not
working? Shotgun solutions only provide enough information to
*speculate* that the old supply was defective. Meanwhile RFI
function (another power supply function) was not defective in
that old supply - according to what you have posted.
Apparently an RFI filter function is missing in the new supply
- as even suggested by its retail price.
A grounding solution is bogus and an obvious waste of time
if power supply even interferes with a car's radio reception.
I had provided one good reason why.
No RFI leak will be that powerful. Power supply would be a
perfect transmitter if missing that essential function.
Shielding or grounding will not accomplish anything sufficient
- would only be time wasted. Power wires would be a perfect
transmitting antenna for a 'defective by design' power
supply. How will you identify AC power wires as a leak? They
are suppose to 'leak' if the internal line filter does not
exist - as pbdelete's inspection would reveal immediately.
But again, pbdelete told you how to address the problem
quickly. (I have suggested how to avoid the problem next
time).
ATX power supply is already inside a metal box. Therefore
supply already has shielding and grounding. Just another
reason why grounding will not be a solution. If you have no
intention of turning this into an electronics project, then do
the filter inspection that pbdelete requested ... now. Or buy
a minimally sufficient supply from a responsible vendor.
Waiting for a manufacturer to respond is a fool's errand -
also called trying to take the easy and convenient way out.
Power supply is a big square wave oscillator typically
running at a base frequency of 20+ KHz. Any wire connected to
that power supply without filters is an antenna. When power
supply is off, then oscillator is not working - therefore no
DC power to computer. DC power to computer comes from that 20+
KHz oscillator. A defective and powered on power supply
becomes an RF transmitting station.
If power supply does not state up front that it meets FCC
Part 15 requirements and European equivalents, then you can
bet the farm. It will not meet specs if it was designed for
bean counter customers. Was FCC requirement and other
critical functions even printed on the power supply's label?
If those functions exist, then they would be printed on that
label.
How would I solve the problem at less cost and time? Go buy
a responsoble supply from a responsible vendor. Throw the RFI
supply in the trash. Chaulk the experience as money spent to
learn the difference between product people verses a bean
counter mentality.
"W. Watson" wrote:
As I think I mentioned above, in another part of this thread, the
vendor has not responded yet. There is no list. I'm waiting for a
reply.
If you are convinced that the power supply is at fault, then I can
simplify matters by taking it back. However, you have not
explained why the original power supply, which is virtually the
same as the one that's giving me the problem, did not have this
problem. It certainly had a problem, but not this one. It
functioned quite well for many months, and then became erratic.
It never caused this much RFI.
...
Ah, I missed part of his message. I saw the part about PFC and put
that to the venodor. As said above, no answer yet. I called the
store where I bought it and they couldn't tell me.
If you don't mind, I'll just wait for the vendor to chime in before
responding to pbdelete's:
"Check the front of the PC box for RFI leaks. It's usually plastic
fantasic all the way.. And above all make sure grounding is
appropiate. Use a multimeter to verify it's working as it should.
Should all other approches fail. Build/buy a sufficient steelbox.
A cheap approach is a wellpap box with tinfoil on the inside."
While we are waiting for that magic moment, perhaps you, or someone,
can tell me: 1. how I'm going to check for RFI leaks 2. make sure
grounding is appropriate, 3. verify it's working as it should? A
wellpap box? Huh? Build or buy a steel box? No thanks. I either
spend money for a better PSU or exchange this for one that does
work. I have no intention of turning this into an electronic
project. If you plan to respond to these questions, because I
really do not intend to follow them. I would like to know though
what a wellpap box is?
...
Well, while I'm waiting to get the answers above, perhaps you can
give me a clue about the following. I plugged the previous PSU
into the wall with the computer turned off. No RFI. I presume
that's because the PSU needs a source to actually power up, right?
--
Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet
"... astronomy is useful because it shows [not only] how small
our bodies are, but how large our minds are." -- Henri Poincare
Web Page: <home.earthlink.net/~mtnviews>
.
