# Stopping RFI from a PC

W

#### W. Watson

Jan 1, 1970
0
I replaced a PSU in my PC, and the result is that the new PSU is more
reliable; however, the RFI seems to have dramatically increased. The PC is
in a building about 100' from the house and 75' from the garage. If I turn
my car AM radio on in the garage, the interference is quite noticeable. Same
with aa AM radio in the bedroom. Since the PC is already in a metal chassis,
what can I do to reduce the interference? Of course, turning off the PC
helps a good deal, but the PC needs to be in operation 7/24.
--
(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

E

#### ehsjr

Jan 1, 1970
0
W. Watson said:
I replaced a PSU in my PC, and the result is that the new PSU is more
reliable; however, the RFI seems to have dramatically increased. The PC
is in a building about 100' from the house and 75' from the garage. If I
turn my car AM radio on in the garage, the interference is quite
noticeable. Same with aa AM radio in the bedroom. Since the PC is
already in a metal chassis, what can I do to reduce the interference? Of
course, turning off the PC helps a good deal, but the PC needs to be in
operation 7/24.

A couple of things come to mind that might help:
Check to make sure the ground at the receptacle is good.
Also, wrap the power cord through a ferrite choke,
as many turns as you can fit. An old TV yoke might
be a source for a large enough ferrite core.

Ed

J

#### John Popelish

Jan 1, 1970
0
W. Watson said:
I replaced a PSU in my PC, and the result is that the new PSU is more
reliable; however, the RFI seems to have dramatically increased. The PC
is in a building about 100' from the house and 75' from the garage. If I
turn my car AM radio on in the garage, the interference is quite
noticeable. Same with aa AM radio in the bedroom. Since the PC is
already in a metal chassis, what can I do to reduce the interference? Of
course, turning off the PC helps a good deal, but the PC needs to be in
operation 7/24.
If you mount a die cast box on the side of the computer and run the
power cord through it, with a good EMI filter inside, you should see
significant improvement, assuming that the noise is getting out
through that path.

A good filter might be something like:
http://rocky.digikey.com/WebLib/CII-Corcom/Web Data/Q Series.pdf

Pick one with a generous current rating (say, double the expected RMS
current to the supply), to keep the inductors from saturating on the
peak current pulses through the line rectifiers.

W

#### W. Watson

Jan 1, 1970
0
ehsjr said:
A couple of things come to mind that might help:
Check to make sure the ground at the receptacle is good.
Also, wrap the power cord through a ferrite choke,
as many turns as you can fit. An old TV yoke might
be a source for a large enough ferrite core.

Ed

Are you thinking of the AC receptacle for the PC?

Note that one of the radios could be considered a portable. The one in the
car. The noise in the house radio is still there when I unplug the radio and
let it operate from batteries. It seems odd that the PC would radiate
through the metal chassis. Of course, it might cause radiation through the
circuit from the outside building into the house. They are all connected.

--
(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

W

#### W. Watson

Jan 1, 1970
0
John said:
If you mount a die cast box on the side of the computer and run the
power cord through it, with a good EMI filter inside, you should see
significant improvement, assuming that the noise is getting out through
that path.

A good filter might be something like:
http://rocky.digikey.com/WebLib/CII-Corcom/Web Data/Q Series.pdf

Pick one with a generous current rating (say, double the expected RMS
current to the supply), to keep the inductors from saturating on the
peak current pulses through the line rectifiers.
Ah, I see now the respondent above you was driving at the PC and not the the
locations where the radios are, since you clarified where to put the filter.

--
(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

W

Jan 1, 1970
0
Sounds like you did not spend $65 retail for that supply. To discount inferior supplies, important functions get forgotten. Sounds like the AC line filter that must be in every minimally acceptable supply was forgotten to cut costs. You would be buying expensive line filters because the line filter did not come in that supply - as is required to meet FCC regulations. What other critical functions are also missing from that supply? Functions discovered later after damage has occurred. J #### Jasen Betts Jan 1, 1970 0 As a rule PC motherboards radiate most at much higher frequencies than AM radio, and since the change made was the power supply it's most likely coming from that. Note that one of the radios could be considered a portable. The one in the car. The noise in the house radio is still there when I unplug the radio and let it operate from batteries. It seems odd that the PC would radiate through the metal chassis. Of course, it might cause radiation through the circuit from the outside building into the house. They are all connected. the wiring could be acting as an antenna or a transission line... do all you can to keep that interferance inside the PC'S box. Bye. Jasen W #### W. Watson Jan 1, 1970 0 w_tom said: Sounds like you did not spend$65 retail for that supply.
To discount inferior supplies, important functions get
forgotten. Sounds like the AC line filter that must be in
every minimally acceptable supply was forgotten to cut costs.
You would be buying expensive line filters because the line
filter did not come in that supply - as is required to meet
FCC regulations.

What other critical functions are also missing from that
supply? Functions discovered later after damage has occurred.
Well, almost. It cost me $49. It's a CE 350 watt PSU, CODEGEN version 3.02. The previous PSU was a CODEGEN 350 watt. -- 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> P #### [email protected] Jan 1, 1970 0 Well, almost. It cost me$49. It's a CE 350 watt PSU, CODEGEN version 3.02.
The previous PSU was a CODEGEN 350 watt.

Does it say if it got PFC? (Power Factor Correction)

Make sure there is a line filter. Like those with two inductors in serial
to the mains.

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.

W

#### W. Watson

Jan 1, 1970
0
I'm checking on the pfc. The version # above is incorrect. It's 2.03.

--
(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

J

#### Jamie

Jan 1, 1970
0
W. Watson said:
I replaced a PSU in my PC, and the result is that the new PSU is more
reliable; however, the RFI seems to have dramatically increased. The PC
is in a building about 100' from the house and 75' from the garage. If I
turn my car AM radio on in the garage, the interference is quite
noticeable. Same with aa AM radio in the bedroom. Since the PC is
already in a metal chassis, what can I do to reduce the interference? Of
course, turning off the PC helps a good deal, but the PC needs to be in
operation 7/24.
get an RFI line filter for the AC cord.
when grounding the case, try to use shielded
ground, that is a piece of coax using the
center as the actual earth ground and connecting
the shield to the ground also at the ground end only,
but not at the computer end..simply pull it back a
bit so that it does not touch and tape it up.
get some Toriodal cores and wrap the cords through
them also.
all of this helps top keep the RF using the cords
as antennas.

W

#### W. Watson

Jan 1, 1970
0
W. Watson said:
I replaced a PSU in my PC, and the result is that the new PSU is more
reliable; however, the RFI seems to have dramatically increased. The PC
is in a building about 100' from the house and 75' from the garage. If I
turn my car AM radio on in the garage, the interference is quite
noticeable. Same with aa AM radio in the bedroom. Since the PC is
already in a metal chassis, what can I do to reduce the interference? Of
course, turning off the PC helps a good deal, but the PC needs to be in
operation 7/24.
Could this difficulty be caused by damage to the chassis? When I bought the
chassis, the owner sold it at a low price, since it had been dropped off a
table. The frame was slightly bent but easily fixed. A year later I began to
suspect that the PSU had also got damaged. Until I put in a new PSU, the RFI
problem was not noticeable.

Is it possible that in putting in the new unit that something didn't get
grounded properly.

--
(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

W

#### w_tom

Jan 1, 1970
0
If RFI noise is that strong, then grounding is irrelevant.
Follow ground wire from computer, through walls, to breaker
box. That long wire an antenna for RFI. So what has grounding
accomplished? Nothing. Your problem exists at the source.
From your own provided information, the power supply was
defective when purchased. Price alone suggests that.

However, did power supply vendor provide a long list of
numerical specs - in writing - including things such as:
Specification compliance: ATX 2.03 & ATX12V v1.1
Short circuit protection on all outputs
Over voltage protection
Over power protection
PFC harmonics compliance: EN61000-3-2 + A1 + A2
EMI/RFI compliance: CE, CISPR22 & FCC part 15 class B
Safety compliance: VDE, TUV, D, N, S, Fi, UL, C-UL & CB
Hold up time, full load: 16ms. typical
Dielectric withstand, input to frame/ground: 1800VAC, 1sec.
Dielectric withstand, input to output: 1800VAC, 1sec.
Ripple/noise: 1%
MTBF, full load @ 25°C amb.: >100k hrs
If not, then again, you all but know that power supply does
not contain many 'essential' functions. Does it even claim -
in writing - to meet those FCC requirements? Quote that text
exactly.

To solve this, then you did everything that pbdelete
suggested. You never post again until you have opened up that
power supply and verified those line filter coils exist. This
is not a game of selecting only what is easiest or
convenient. This is a game where you do everything and then
post back. He did not waste time posting those actions. You
want to solve the problem. Then do everything he has
recommended.

The power supply did not cost $65 full retail. Therefore it is most likely defective when designed. Again, this is not a number you can fudge as you 'feel'. That was a blunt hard number. What is the full retail price. Less than$65? Then
is it likely missing essential functions. What a
coincidence. Your symptoms are exactly what would happen if
that line filter (as made necessary by FCC Part 15) did not
exist. Common for power supplies marketed to bean counter
types who are experts because they look at two numbers -
dollars and watts. Such supplies are not marketed to those
who deal in reality - demand those numerical specs in writing.

Well you have this supply. Does it have the line filter as
pbdelete said to inspect for? If not, then every other post -
especially those grounding suggestions - is time wasted.

W

#### W. Watson

Jan 1, 1970
0
w_tom said:
If RFI noise is that strong, then grounding is irrelevant.
Follow ground wire from computer, through walls, to breaker
box. That long wire an antenna for RFI. So what has grounding
accomplished? Nothing. Your problem exists at the source.
From your own provided information, the power supply was
defective when purchased. Price alone suggests that.
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.
However, did power supply vendor provide a long list of
numerical specs - in writing - including things such as:
Specification compliance: ATX 2.03 & ATX12V v1.1
Short circuit protection on all outputs
Over voltage protection
Over power protection
PFC harmonics compliance: EN61000-3-2 + A1 + A2
EMI/RFI compliance: CE, CISPR22 & FCC part 15 class B
Safety compliance: VDE, TUV, D, N, S, Fi, UL, C-UL & CB
Hold up time, full load: 16ms. typical
Dielectric withstand, input to frame/ground: 1800VAC, 1sec.
Dielectric withstand, input to output: 1800VAC, 1sec.
Ripple/noise: 1%
MTBF, full load @ 25°C amb.: >100k hrs
If not, then again, you all but know that power supply does
not contain many 'essential' functions. Does it even claim -
in writing - to meet those FCC requirements? Quote that text
exactly.

To solve this, then you did everything that pbdelete
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?

Continued below.
suggested. You never post again until you have opened up that
power supply and verified those line filter coils exist. This
is not a game of selecting only what is easiest or
convenient. This is a game where you do everything and then
post back. He did not waste time posting those actions. You
want to solve the problem. Then do everything he has
recommended. No comment.

The power supply did not cost $65 full retail. Therefore it is most likely defective when designed. Again, this is not a number you can fudge as you 'feel'. That was a blunt hard number. What is the full retail price. Less than$65? Then
is it likely missing essential functions. What a
coincidence. Your symptoms are exactly what would happen if
that line filter (as made necessary by FCC Part 15) did not
exist. Common for power supplies marketed to bean counter
types who are experts because they look at two numbers -
dollars and watts. Such supplies are not marketed to those
who deal in reality - demand those numerical specs in writing. This is not news.

Well you have this supply. Does it have the line filter as
pbdelete said to inspect for? If not, then every other post - Wait as above.
especially those grounding suggestions - is time wasted.
No comment.

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?

--
(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

W

#### w_tom

Jan 1, 1970
0
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

#### W. Watson

Jan 1, 1970
0
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.

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

w_tom said:
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.

--
(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

W

#### w_tom

Jan 1, 1970
0
Noise is 'routinely' blocked inside the metal (power supply)
box by the line filter - if filter exists. You are fooling
yourself if you think some coil on the power cord or grounding
is going to solve the problem. The power supply appears to be
defective when designed. It appears to be another classic
example of power supplies designed for MBAs types who call
themselves 'computer literate'. Overseas manufacturers have
discovered a lucrative market of technically naive computer
'experts' AND have dumped product into that market for higher
profits.

You don't need a local electronics store. The internet is
chock full of responsible vendors who sell minimally
acceptable supplies. Supplies that meet Intel ATX power
supply specs - and say so. Supplies that meet FCC Part 15 and
the even more stringent European standards. Supplies that
must also meet ISO, CE, UL, and other standards - all in the
same box. Where are those approval labels on your power
supply? What other problems will those missing standard
(functions) create?

A previous post listed other functions that the power supply
must provide. For example, does that supply have over voltage
protection (OVP)? If not, then a power supply problem could
destroy every other component inside a computer - later. OVP
was standard even 30+ years ago so that a power supply failure
to 'never' damage other computer parts. And yet power
supplies missing essential functions such as AC line filter
would also 'forget' to include other important functions.

How would you know if that supply has OVP? As pbdelete
noted - open the power supply to identify an AC line filter:
Make sure there is a line filter. Like those with two
inductors in serial to the mains.
If no filter, then you are not going to fix that supply.
Other essential functions, such as OVP, are also probably
missing. A supply designed for bean counters - people who are
so often the reasons for failure.

Noted earlier was how a power supply sells at lower price
for greater profits. OVP is but another function routinely
missing on power supplies designed for bean counter
consumption. Power supply that provides no written
specifications because so many such 'computer experts' only
look at two numbers - dollars and watts. People who will
rationalize their decision rather than take hard and
conclusive actions.

If that power supply does not have an AC line filter as
pbdelete asked to inspect for, then that missing function may
be part of an iceberg. Your only viable solution is a new
power supply from a responsible power supply vendor and
manufacturer. Some computer parts houses don't even stock
such supplies.

Meanwhile, what is accomplished by learning AC house
wiring? Learn which wires are better and worse transmitting
antennas. Again - and it should be so painfully obvious - no
grounding was going to solve your RFI. That ground wire
inside the wall only becomes a transmitting antenna - as was
stated previously.

There is no plug-in or power cord solution for a missing
filter that was required and standard even generations ago.
There is no "coil to put around the the AC cord". A supply is
causing RFI interference. Then the entire supply is detective
by design. Completely unacceptable, a reason for more future
problems, and a classic example of why people with MBA
mentalities create so many failures. Patching a solution on
the power cord is called 'curing symptoms' or a 'kludge'. A
solution must exist at the problem - inside that power supply
box - where the solution would have cost so little money.

P

#### [email protected]

Jan 1, 1970
0
Jamie said:
W. Watson wrote:
get an RFI line filter for the AC cord.
when grounding the case, try to use shielded
ground, that is a piece of coax using the
center as the actual earth ground and connecting
the shield to the ground also at the ground end only,
but not at the computer end..simply pull it back a
bit so that it does not touch and tape it up.
get some Toriodal cores and wrap the cords through
them also.
all of this helps top keep the RF using the cords
as antennas.

Why not shileded power cables?, especially since it's likely not complient to
disconnect earth on the mains connector. Especially if something goes wrong.

P

#### [email protected]

Jan 1, 1970
0
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

Use an AM-radio, disturbances => RFI. (simple but working)
You could also wire a simple directional antenna from steel wires if you
want to get more accurancy easy.
2. make sure grounding is appropriate,

Push down a pole >2meter into the ground measure between jack and pole.
Also check between jack and incoming terminal. Btw, this depend on the specific
electrical code in your country. So be careful.
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?

Maybe the english word is cardboard/pasteboard. Thick paper used in packageing
at least. Combined with household aluminium foil you can create a quick and
cheap faradays cage to block RFI.

However as suggested in later posts. IF the powersupply "sends" it's RFI back
out through the powercord. Then no shielded box etc.. will help. Unless you
add an line filter. I think many are two coils in parallel combined with
suitable capacitors to shortcircuit highfrequencys.

I had a look into this when investigating powercontrol via igbt and mosfet.
Where one technique is modulated pwm to produce sinus. Which is nice.. except
for the RFI

If you have a oscilloscope then you can verify many of these things yourself.
At least PFC and Line filtering should be visable.
Btw, does the disturbances affect FM-band too ?

J

#### Jasen Betts

Jan 1, 1970
0
Why not shileded power cables?, especially since it's likely not complient to
disconnect earth on the mains connector. Especially if something goes wrong.

IT all depends on what mode the RFI takes,

If it;s balanced on the live and neutral conductors the only thing that'll
stop it is a proper EMI filter that filteres each conductor separately.

if it's common to all three conductors then the toroid etc will stop it
abd the EMI filter may not (but I count this as unlikely)

all that shielding does is keep the cable from radiating, if it's plugged
into an outet shared with other unshielded cables they will radiate the RFI...

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