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PC Power Problems Special Report on the Conspiracy Behind Bad Power Supplies |
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PC Power Problems Special Report on the Conspiracy Behind Bad Power Supplies |
We have provided this page for those who are experiencing the symptoms of BAD POWER in a PC. If you do not know whether you have such symptoms, or if you want a solution, read on.
(But, maybe something can be done...)
Copyright © 1992 -
and All rights reserved by
by Robert Hurt
If you do, then your system POWER SUPPLY may be to blame, and that may be the result of a world-wide CONSPIRACY and fraud! To find out more, READ ON.
In this article I will tell you a few important things I have learned about PC power supplies and the weird, insidious problems they cause. Then I will recommend some steps you can take to identify, cure, and prevent them. I will even tell you where to get some GOOD power supplies.
Here is an overview of the power supply. The power supply is that shiny metal box bolted in place in your PC's case, at the back. Its purpose is to convert high voltage alternating current (110 VAC in the USA, 240VAC or more in Europe) into low voltage direct current needed by the computer's internal components.
The power cord from the wall plugs into it. It has a fan in it. A bundle of wires come out of it and plug onto your motherboard. The original PCs had TWO connectors that plug onto the motherboard. The black wires of each go adjacent to each other. The orange wire goes toward the back of the computer. Some other plugs are available for connecting power to the floppy and hard drives. That is the power supply.
While the rest of the PC uses low voltages (+5, +12, -5, -12), DANGEROUS HIGH VOLTAGES are inside the power supply, so you should never remove the cover unless you are a qualified power supply repair technician.
This is no joke, and the conspiracy is very real. IBM provided the original PC power supply (remember, this is way back in 1981, possibly before many of you were BORN) with specifications that limited the deviation of its voltage outputs to approximately 5% or 10% of its outputs, 5% for positive voltages and 10% for negative voltages. IBM was saying: "These voltages will not vary more than 5% of what they are supposed to be". 5% of +12 Volts is .6 V (six tenths of a volt). And, way back when, power supplies were very expensive.
Today however, the +12 VDC output is not at all regulated in 90% or more of the supplies that are made, and the +12 VDC output cannot be relied upon to stay with .6 Volts of 12 Volts. Why do you suppose this is?
The reason is simple: USA buyers almost NEVER test the power supply outputs to see if they are correct. Most of them think the power supply is rock solid and never fails and has perfect outputs. Well, guess again.
Today, you can buy a power supply wholesale for $20 or less. Think about this. You have a wiring harness, heavy-duty switch, fan, and metal box. All that costs money. It does not leave much for ELECTRONIC CIRCUITS, does it?
Plus, you have one more cost: SHIPPING FROM CHINA! That's right. Most of the world's power supplies are designed and built in Taiwan, mainland China, Korea, and other far east countries. One thing they know is that WE, the American and European consumer markets, the biggest computer markets today, NEVER TEST POWER SUPPLIES. They know that WE think if we plug the power supply into the motherboard and turn power on and nothing starts smoking, the power supply must be perfect. So, they have stripped every possible component out of the power supply, and they manufacture it in the fastest possible way, and they sell it at the lowest possible price so no one can compete against them.
These power supplies are under-regulated, noisy, and provide little protection against bad incoming AC voltage variations. IBM never provided a specification for noise (AC voltage on the DC outputs), but the ISA (industry standard pc architecture) specification by the Institute of Electrical and Electronic Engineers, IEEE P996, specifies the noise to be a maximum of 1% (one percent) of the output voltage. The +5 VDC output should have no more than 50 miliVolts of AC on the DC outputs. When we ran our own test on an assortment of of 30 new power supplies, we found that 70% of those supplies had more than 1% noise on one or more outputs.
In order to sell a power supply in the USA, a manufacturer must submit the system containing it to a testing laboratory approved by the Federal Communications Commission (FCC). The lab tests it to ensure it does not emit high frequency signals into the air or back into the AC power line because such emissions will interfere with Radio and Television reception. The requirements are tougher on consumer computers (FCC Class B) than they are for business computers (FCC Class A) because radios and TVs are not often found in businesses.
Most FCC-approved testing laboratories now take photographs of the internal component layout of the power supplies they test and approve. The reason is: historically, a power supply will fail their tests the first time through the lab, and the manufacturer must rework the circuits or metal housing in order to prevent the emissions. Such rework and the necessary retesting is very expensive. Then, once the supply passes the tests, the laboratory will issue an FCC certification number to the manufacturer. Quite often, the manufacturer will go right back to Taiwan or China, switch the circuitry back to its original noisy configuration and manufacture the power supply THAT way in order to SAVE MONEY. They really don't care if the power supply interferes with our TV and radio reception. If you think this is wrong, try using a portable wireless telephone near your computer, and you will KNOW there is unwanted electromagnetic noise nearby.
Today, all PC manufacturers must have FCC class B certification on computers being sold to consumers for the home market, and that constitutes most of the computers offered for sale. When have you ever seen a sign saying "this computer is for use in the office only"? You can build your own computer and not get it certified, but anyone who sells one legally MUST have it certified. That is why most PC component suppliers sell the case and power supply as a combined unit.
When the FCC officials actually test a computer in the consumer market and find that it does not pass certification, they issue an order that prevents the computer from being imported into the USA, and the fine is $2000 per system sold in violation of FCC emission limits. They will take the system back to the certification laboratory and demand an accounting as to why that system was granted the certificate. Without the photos, there would be (and has been) finger-pointing, with the manufacturer saying "It's not MY fault - the lab certified it", and the lab saying "We certified Something, but not THAT". The photographs often show conclusively that the power supply was altered and the one being shipped is NOT the one that was certified.
You know how efficient and effective the Government is, don't you? The FCC has very few field officials to police the conformance of systems to FCC regulations. For every one caught in violation, thousands escape detection. So, America is loaded with systems that fill the air with electronic noise.
But, guess what? The FCC does not care about noise and poorly regulated voltages INSIDE the computer! There are no regulations for that. There is NO ONE AT ALL testing for that, and especially no one (or virtually no one) testing for that in the field, AFTER the PC has been sold to the consumer.
Except us. But more on that later.
From the above you should realize that even big computer makers have power supply problems. They cannot compete effectively against Chinese manufacturers, so guess where most of them buy their power supplies? Don't be surprised to find junk power supplies in ANY PC these days, whether from IBM, Compaq, Digital, Packard Bell, Dell, Gateway 2000, Micron, or anyone. I am sure they WANT their systems to be good, and the industry is always changing to meet and deal with sales, marketing, support, and cash flow pressures. As more become aware of the problems, better solutions will be developed. Meanwhile, all YOU can do is trust them, AND TEST YOUR OWN POWER SUPPLIES.
Now, let's see what the power supplies actually do and how that affects you.
The power supply creates 4 or 5 DC voltages, used as follows:
+5 VDC - Logic circuits (the computer chips), some notebook drive motors
ATX systems are new in the industry. Intel's ATX specification was created to allow more convenient access to built-in I/O devices on the motherboard, and to accomodate power supplies that generate +3 VDC for use with modern low-voltage CPUs and chipsets. An ATX-compatible power supply offers a 20-pin motherboard connector and provides +3 VDC. The original ISA-compatible supply offers a 12-pin connector (normally two 6-pin connectors side by side) and NO +3 VDC output. All non-ATX systems that require +3V have an on-board power supply and regulator (on the motherboard) that convert +5V into +3V for the new CPUs. The +3V CPUs consume less energy and generate less heat than the +5V parts.
The power supply output wires are different colors to identify which voltage they are. The colors normally (but not always) used are:
The connector Pinout on an AT supply is as follows:
From the above you can tell what parts of the computer do not work if different voltages go out or become unstable. +5 or +3 can go out and the computer will not work at all. +12 can go out and the drive motors will not spin but the system will try to boot; also, the serial ports will not work.. -5 can go out and you will never notice any bad side effect. -12 can go out and the serial ports will not work but everything else will be okay.
Most PC power supplies are known as "switch mode" supplies because of the technology that allows them to create high current outputs at low weight. The circuitry inside a power supply consists of three sections: voltage reduction, voltage regulation, and voltage conversion and output.
The voltage reduction circuit converts the high 110 to 250 VAC input to a lower voltage. It should protect the rest of the circuitry from voltage surges on the input and cleanly shut off the power supply outputs if the input voltage drops too low.
The voltage regulation circuit monitors the DC output levels and adjusts the amount of current flowing in the output transformer to keep the DC output levels constant. There should be one regulator for each output voltage.
The voltage conversion and output circuit converts 50 or 60 Hertz AC to 30 kiloHertz AC through an oscillating dual-transistor "switcher" and transformer coils. It then converts the AC to DC. Finally, it filters all the AC ripple out of the DC voltage to make it perfectly smooth, flat DC. The DC output circuit should monitor the output and shut off the voltage if the outputs get shorted together by accident.
In addition to providing +5, -5, +12, -12, +3 (on ATX supplies), and ground signals, it also provides a "Power Good" signal which should go to +5 VDC if the output levels are correct for proper operation of the computer. If the Power Good signal goes to zero volts, it causes the circuitry on the motherboard to issue the system Reset signal and shut off clock to the CPU. The result of this is the same as your pressing and holding the reset button on the front panel: it stops the computer from running. If the Power Good signal goes back to normal, the computer starts running and reboots.
Efforts to reduce the cost of power supplies have resulted in fewer components. Designers sometime make mistakes in the design that cause the protection, regulation, or fltering, or protection circuits to work improperly or not at all. For example, some designs have no regulator on any voltage but +5 and +3 VDC outputs. Some have no "brown-out" protection, and produce dangerously low output voltages if the inputs fall too low. Some have no input surge protection and allow power line spikes to be fed to the DC outputs. Some may become damaged if you short the outputs together. Some emit high frequency electromagnetic radiation, or allow high frequency AC signals from the motherboard to be fed back into the AC power line to interfere with television and radio running off the same AC power. Some do not properly filter the 30 kHz ripple (often referred to as "noise") from the output voltages uniformly for all levels of load (current consumption) on the outputs. Many of these flaws are undetectable except under extreme or unusual circumstances.
The effort to reduce cost also pressures manufacturers to make mistakes in component selection or assembly. Such manufacturing defects prevent proper operation of the supply, cause the voltages to be incorrect or noisy.
Power supplies get hot because of the high current flowing through them. As certain components get older, the do not operate as well as they originally did, causing outputs to be incorrectly filtered or regulated.
A clogged air flow path or defective fan can increase the heat inside the supply and the whole system. Higher heat shortens component life, and it makes some components not operate properly till cooled down. Many modern systems require special additional fans to be fitted to the CPU chips in order to keep them cool enough for reliable operation.
This topic will summarize the main types of power supply failure and explain the effects.
Regulation is the act of keeping the power supply's output voltages constantly at a particular DC level.. To do this properly, each output voltage must have its own regulator. Most power supplies today only regulate +5V, but some are available that regulate all of them.
Current drain from the power supply is known as "load". When the hard drive heads move to a new position, the load increases momentarily because of the current to the head positioner motor. Because of power supply design, the increase in load causes the output voltage to drop momentarily. It is the job of the regulator circuit inside the power supply to push the voltage back up instantly, so the drive motor does not "see" a fluctuating voltage. If the regulator is operating properly, the output will be a constant DC level, regardless of the changes in load.
One major problem with modern cheap power supplies is that +12 VDC and +5 DC circuits share the same output transformer, but the only the +5 output has a regulator. Thus, if the load on +5 is low, as is the case in most systems, the +5 output tends to rise, the regulator pulls it back down by reducing current in the transformer, and as a result, the +12 VDC output is pulled down right along with it. This causes the +12 VDC output to be too low. In case you are wondering,, low +12 VDC will affect drive motors.
A side issue to regulation is the Power Good signal. It is supposed to be present when the DC outputs are good and not present when they are not good. Obviously, if the +12 VDC output drops too low, the power is not good. However, many power supply manufacturers only cause Power Good to go away when the outputs are so catastrophically bad that the system will not run at all. I have seen power supplies with the Power Good signal completely removed, and the adjacent +5V signal jumpered over to the Power Good pin in the motherboard connector.
Brown-out is a dramatically reduced AC source voltage. It is caused by excessive load on the power company, such as during hot summer days when everyone in town is running the air conditioner.
In a good quality power supply, brown-out will not affect the DC outputs at all until it drops to a certain level. Exactly at that level, the power supply cleanly shuts off all DC outputs, immediately shutting down the system.
In a bad quality power supply, brown-out makes the DC outputs drop too low, but the supply does not cleanly shut down. When the outputs drop, especially +5V, some of the circuits in the system begin to malfunction, causing data loss and data corruption, especially when writing to disk drives. It also makes the drive motors overheat, thereby reducing their expected life or burning them up (yes, LOW voltage causes overheating and premature failure). The system can continue operating and unbeknownst to you, the data is being corrupted and parts are being damaged.
A transient is a voltage surge of short duration that exceeds the nominal voltage by a large amount, perhaps 10% to 20% or more. A transient is commonly referred to as a "spike" or a "glitch". There are many kinds of transients, some dangerous to your computer, and some dangerous only to your data. Transients are bad and should not occur on the DC outputs of a power supply.
Transients on the DC outputs are usually caused by surges in the AC power feeding the power supply. A defective power supply can cause transients too, but it is rare compared to AC transients. AC transients are caused when the power company switches power off and on, or by a motorized appliance (air conditioner, refrigerator, air compressor, etc) near the computer switching on or off. Lightning strikes near or on the power lines also cause them.
The power supply should prevent transients from passing through to the DC outputs. A transient that passes through the supply can damage the motherboard or drive motors. This happens all the time with lightning, and it is forgivable for a power supply to pass THAT through (lightning burns out modems attached to phone lines, and through the modem it burns out the computer, as well). But the more common circumstance is for the transient to interrupt operation of the system in some way.
Noise is unwanted AC signal riding on the DC level. It is commonly referred to as power supply ripple.
The input section of the power supply has to filter out the AC line frequency of 50 Hz to 60 Hz. Inside the power supply a pair of power transistors that switch on and off at a relatively high frequency, usually around 30 thousand times a second (30 kHz). The output filter is supposed to block the 30kHz AC signal.
Sometimes the filtering does not work properly, thereby allowing AC power line frequency or internal switching frequency to be mixed with the DC outputs. This can create severe problems in operation of the system.
If you look on your motherboard you will see tiny components adjacent to each chip. These are filter capacitors, and their job is to filter out high frequency switching transients produced inside the chips, to prevent transients from being put on the DC power lines and thereby affecting adjacent chips. The switching transients are rather like the water hammer you hear in some houses when you turn the water on and off quickly. The filter capacitors absorb the shock wave of the "electronic hammer".
These filters are NOT intended to filter out power supply ripple. When you have power supply ripple entering the motherboard on the +5V or +3V power lines, that ripple can so alter the DC voltages that it causes the transistor circuits to malfunction. The result is lost or corrupted data.
The power supply not only has to filter noise out of the DC outputs, but it also has to prevent its own switching noise AND any high frequency or radio frequency motherboard or disk drive noise from feeding back into the AC power line. Such feedback will not affect the computer, but it can affect nearby radios, televisions, cellular phones, and portable phones. Such emissions are a violation of FCC regulations and similar regulations outside the USA.
Radiation is the radio frequency electromagnetic energy in the air. If the power supply and computer are not properly designed, the radio frequency energy generated by computer components can leak out into the air and affect radio and television type devices nearby. This also is a violation of the governments' emissions regulations.
When components inside the power supply start getting old or deteriorating from excessive heat, they break down and fail to function properly. Often the power supply will keep on working, but not correctly. One indication of an aging supply is when you hear noise other than fan noise coming from inside the supply.
The most typical kind of such noise is a repeated chirping sound. A less typical one is a low hiss or hum. Such a supply should be replaced. Note: the power supply's internal switcher circuit can issue a high-frequency sound, but it is normally beyond the range that humans can hear.
This important device mounted inside the back of the power supply pulls air through the supply from the ducts inside the computer. If the fan stops working, the air flow will stop, the power supply and the computer circuits will overheat, and the computer will die. The power supply may die too, and the damage may be permanent. Before it dies, it may operate erratically, causing mysterious hangups, data corruption, and data loss.
Computer cases normally are not outfitted with air flow filters, so any dust and dirt in the air adjacent to to the computer will flow into the system. Normally, the particles catch onto the edges of the air flow holes on the case and on the power supply, building up as time goes by. It also collects on PC boards and circuit components. The thicker it gets, the more heat is trapped inside the components. As they overheat, they begin to malfunction, and they fail prematurely. The system must be blown and vacuumed out occasionally to prevent this.
While it is not a problem with the supply itself, it may be that some device in the system is shorting a DC output to ground. Good power supplies simply shut off that voltage till the short is removed. Cheap power supplies may blow an internal fuse (DANGER: don't try to replace one unless you are a qualified maintenance technician - the voltages inside the supply can kill you), or become permanently damaged.
Most people assume the power supply is okay if the system is running. That is a wrong assumption much of the time. Some power supply failures are immediately obvious, but others cause all kinds of problems and ineffective remedial actions before being discovered. Among the many symptoms of a bad supply are: noisey fan (grinding, screeching), NO fan sound at all, chirping sound, erratic system or component operation, intermittent system operation, one part works but another does not, burning smell, and dead system. The problem is: almost anything in the system can cause MOST of these problems.
Aside from the obvious problem of a completely dead system, there are two ways to detect a bad : the HARD way and the EASY way.
You can buy a voltmeter and a storage oscilloscope, learn how to use them, read up on the specifications and testing procedures , then test the supply, replace it if defective, and let that equipment sit around till next time you use it. Cost: $500 to $2000+, depending on how fancy the equipment is.
You can buy pcwiz inc's PC PowerCheck test card. You plug the card into a slot, or plug the power supply directly onto the card, and switch power on. You look at the lights. They tell you what is out of specification. Then you use it to help check out your friends' power supplies (you will get more friends this way), and you use it to make more service money because it is WORTH the price.
The lights tell you the status of the system Reset signal and the Power Good signal. They show you if each of the 4 voltages is
Four summary lights on the rear edge of the card show if any errors occurred. A switch on the rear edge lets you reset the detector circuits to clear any error lights. The circuits on the card are pre-adjusted to IBM's original over- and under-voltage limits for power supply outputs. They are set to detect 2% or more noise (IBM had no spec for that) because too many supplies fail at 1%. They will also detect a transient that is .75 VDC over nominal and lasts for 200 nanoseconds or longer.
Jumpers on the card let the high and low detectors operate in trap or continuous monitor mode. The alarm lights operate as follows:
PC PowerCheck has small load resistors built onto the card, and an ISA motherboard connector so you can plug the supply directly onto the card and load it down enough to test it. This allows you to bench test several power supplies without risking damage to your computer by plugging an unknown supply into it for testing.
And, here's the best part, the price. Including 2 year warranty and unlimited USA-toll-free technical support FOREVER, FREE -
Cost: $299 retail.
To see a picture of the card, visit our web site:
http://www.datadepo.com/pcpck.htm
If you have or suspect you have power supply problems, or if you have to troubleshoot computer problems, then ORDER PC PowerCheck now (order on-line at http://order.datadepo.com. It will save you a lot of guessing as it has thousands of professionals around the world, and it will let you rip those cheap power supplies out by the roots so you can replace them with good ones.
Oh, yes, the "good" power supplies. There are quite a few good ones, and good manufacturers, but I don't know all of them. I can, however, recommend several companies whose products I have tested and found to be much better than average.
1. PC Power and Cooling is America's premier power supply manufacturer, offering a range of top-quality power supplies, cooling fans, cases, and power/temperature monitors.
PC Power and Cooling Inc
5995 Avenida Encinas, Carlsbad, CA 92008
(619) 931-5700, (800) 722-6555, Fax (619)931-6988
http://www.pcpowercooling.com
2. Antron, formerly known as Senstron, is a Chinese-American power supply engineering and manufacturing company. Among their broad range of supplies are some top-quality offerings at reasonable prices.
Antron Electronics
95 Mayfield Avenue, Edison, NJ 08837
(908) 417-0411
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Robert Hurt has served various areas of the computer industry in a number of organizations since 1962, including the U.S. Navy, Control Data Corporation, Hewlett-Packard Company, Fluke Corporation, Orchid Technology, Award Software, Mouse Systems, Deico Electronics, Landmark Research, pcwiz inc, and several other startups. His experiences include technical support, technical writing, hardware and software engineering, manufacturing, teaching, lecturing, sales, marketing, and executive management. He has worked with computing technology including BIOS, diagnostics, and system-level application programming, web site development, missile fire control systems aboard Polaris submarines, 4-bit and 8-bit microprocessor-based systems, desktop computers, PCs, minicomputers, and the world's most powerful mainframes. He has written numerous technical manuals, sales training manuals, magazine articles, data sheets, white papers, and other literary works.
Mr. Hurt developed and acquired the original diagnostic technology for Landmark Research, founded pcwiz inc in 1991, and is now pcwiz inc's president and CEO.
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