Power Supplies

The PC Power Supply and the Super7 System

Problems with your PC’s power should not be overlooked as a potential source of virtually any hardware-related PC troubles.  While most of us tend to never give our Power Supply a second thought, it is good to have at least a basic understanding of the computer’s Power Supply and power requirements.  There can also be problems with your power external to the PC itself which should also bear some consideration.

Between the Wall and Your PC
The raw power sent to your home or office by your local electric company while susceptible to spikes, surges, line noise, brown or black-outs is for the most part is just fine provided you use a good quality surge protector or UPS (uninterruptible power supply) but you should be aware that problems can occur between the wall socket and the PC power supply.  The first place to look for a power problem is in the black power cord supplied with your PC case.  Most of these are equal to the task but if you bought an inexpensive case you may have a substandard power cord.  If the cord is warm to the touch you may want to look into purchasing a more heavy-duty one.  Also, where your computer resides can have some effect of the quality of power it receives.  Proximity to radio transmitters or electric motors – even of the household variety can affect the line noise and EMI (electromagnetic interference), so keep your distance from items such as CB or HAM radios, fans, air conditioners or refrigerators. Some devices in your own home or office produce line noise then pass it on to other devices throughout the power system. Better quality surge protectors, power filters or UPS systems will isolate devices that plug into them to prevent this type of power contamination.  It is also wise to avoid overloading your surge protector or extension cords. If you even wonder that you have too many devices plugged in to a single source, you probably do and this is one area where it truly doesn’t pay to be cheap.

The Power Supply
Your PC’s internal power supply is responsible for converting your standard household current into a form of electricity that your computer can use. Since the power supply is responsible for providing power to every device in your computer; if it has a problem or is of substandard design or quality you may experience problems that you may not realize are actually the fault of the electrical system.

Switching power supplies, though capable higher efficiency and reduced size, were until very recently notorious for generating excessive electromagnetic interference (EMI) that affected the normal operation of nearby electronic equipment such as the circuitry on your mainboard. Methods utilized for reducing EMI use circuit design approaches such as adding snubbers and input filters, adopting special pulse-width-modulation strategies, etc. While these methods reduced EMI, they complicated the design process as well as increased the production cost. In the past, these anti-noise components were added on a trial-and-error basis during the final stage of the design process when EMI was found to exceed the compliance limits (e.g., FCC and VDE). While adding to the cost of earlier power supplies, many of these components were standardized into today’s modern ATX power supply.

A high quality power supply with sufficient output capacity to meet the demands of your system should provide years of service and is essential for the proper operation of your PC.  It is interesting to note the cost of good replacement power supplies is near to, and can sometimes even exceed the cost of a new case.  What does this tell us???  Poor quality power supplies can cause numerous problems in both your hardware components and the way your software performs.  Another consideration is your future expandability.  High wattage, quality power supplies afford you all of the options available on today’s modern PC such as multiple hard drives, CD rewriters and DVD players and internal ZIP drives. 

 Your PC’s power supply also plays an integral role in cooling your system.  The fan integrated with the power supply’s housing is for many PCs the major force in moving air into and out of the case. 

Power supplies support either 110v, 220v or, more often, both. Dual-voltage supplies normally have a selector switch mounted in the back that sets which voltage you are using. If the power supply has a 110/220 switch, make sure it is set correctly!!! An improperly set switch will prevent the power supply from operating.  Here in the US, the possibility of damaging the device with an improperly set switch is slim but a power supply set for 110v that receives 220v can easily burn up.

Not simply a power converter (such as your printer or scanner might use), the PC power supply is responsible for the conversion of standard household current (110v AC at 60 cycles per second here in the US) into a variety of low-voltage DC currents of varying degrees of strength.

Booting Up
A PC switching power supply will only function properly if there are components attached which will draw power from it.  This is why a system without a hard drive installed will normally fail to power up properly.

Depending on the form factor of your system your PC needs some form of switch to turn itself on.  While older 386 and 486 systems used a switch that was housed within the power supply itself, today’s AT form factor system use physical pole/throw switches mounted on the front of the case to send current to the power supply.  ATX form factor systems use a somewhat different design in that the switch on the outside of the case is connected to the mainboard rather than the power supply.  This gives the BIOS located on the mainboard control of the power supply as mentioned above. Since the ATX form factor power supply is controlled by signaling from the mainboard and BIOS, you should be aware that power is being supplied to the mainboard even when the system is off. You should never work on a PC without first disconnecting the power cord from the back of the case.

When you first power-on your machine the power supply requires a brief period of time to stabilize all of the required voltages so it lets the mainboard know when it is ready broadcasting a “power good” signal.  Until the mainboard receives this signal it prevents the other components from using the unstable power thereby offering a measure of protection.  While this period of time is brief – half a second or so – when you consider that a modern 600MHz CPU can process 300 million instructions in that amount of time, improper power levels could cause myriad problems.  The power supply can switch off the power good signal in case of power surges or steep reductions in the current coming to it from the wall socket.  When this occurs the mainboard shuts down and will not start until the power good signal is once again broadcast.  Most of the time, when this happens, you will need to reset the system

Troubleshooting the PC Power Supply 

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