More about SATA Cables & Connectors

SATA cables are long, thin, 7-pin cables.

One end plugs into a port on the motherboard, usually labeled SATA, and the other into the back of a storage device like an SATA hard drive.

Power Supply Ratings

The 300-watt and larger units are recommended for fully optioned desktops or tower systems. These supplies run any combination of motherboard and expansion card, as well as a large number of disk drives and other peripherals.

BTX (for Balanced Technology Extended)

BTX (for Balanced Technology Extended) new power supply standard by Intel in 2004. It is replacement of Micro-ATX power supply. Basically it designed for Pentium 4 and core systems. In addition 24pins mother board connector and connector for SATA devices. 

BTX Main Power Connector

Description: sata-powerDescription: BTX1

Power Supply Troubleshooting

Troubleshooting the power supply basically means isolating the supply as the cause of problems within a system and, if necessary, replacing it.

In many cases a parity check error message can indicate a problem with the power supply. This might seem strange because the parity check message specifically refers to memory that has failed. The connection is that the power supply powers the memory, and memory with inadequate power fails. It takes some experience to know when this type of failure is power related and not caused by the memory. One clue is the repeatability of the problem. If the parity check message (or other problem) appears frequently and identifies the same memory location each time, it would be indicated that the defective memory is the problem. However, if the problem seems random, or if the memory location the error message points to as having failed seems random, it would indicate the defective power supply. The following is a list of PC problems that often are related to the power supply:

  • Any power-on or system startup failures or lockups.
  • Spontaneous rebooting or intermittent lockups during normal operation.
  • Intermittent parity check or other memory-type errors.
  • Hard disk and fan simultaneously failing to spin (no +12V).
  • Overheating due to fan failure.
  • Small brownouts cause the system to reset.
  • Electric shocks felt on the system case or connectors.
  • Slight static discharges disrupt system operation.

Irregular system problem indicate that the supply is defective.

Following symptoms point right to the power supply as a possible cause:

  • System is completely dead (no fan, no cursor)
  • Smoke
  • Blown circuit breakers

If you suspect a power supply problem, some of the simple measurements and the more sophisticated tests outlined in this section can help you determine whether the power supply is at fault. Because these measurements might not detect some intermittent failures, you might have to use a spare power supply for a long-term evaluation. If the symptoms and problems disappear when a known good spare unit is installed, you have found the source of your problem.

Following points can help to zero in on common power supply related problems: –

1. Check AC power input. Make sure the cord is firmly seated in the wall socket and in the power supply socket. Try a different cord.

2. Check DC power connections. Make sure the motherboard and disk drive power connectors are firmly seated and making good contact. Check for loose screws.

3. Check DC power output. Use a digital multi-meter to check for proper voltages. If it’s below spec, replace the power supply.

4. Check installed peripherals. Remove all boards and drives and retest the system. If it works, add back in items one at a time until the system fails again. The last item added before the failure returns is likely defective.

Many types of symptoms can indicate problems with the power supply. Because the power supply literally powers everything else in the system, everything from disk drive problems to memory problems to motherboard problems can often be traced back to the power supply as the root cause.

Voltage Tolerance of Power supply

Continue by measuring the voltage ranges of the pins on the motherboard and drive power connectors. If you are measuring voltages for testing purposes, any reading within 10% of the specified voltage is considered acceptable, although most manufacturers of high-quality power supplies specify a tighter 5% tolerance. For ATX power supplies, the specification requires that voltages must be within 5% of the rating, except for the 3.3V current, which must be within 4%. The following table shows the voltage ranges within these tolerances.

Voltage ranges for an ATX power supplies

Loose Tolerance                    Tight Tolerance

Desired Voltage            Min. (10%)Max. (+8%)   Min. (5%)Max. (+5%)

The Power Good signal has tolerances that are different from the other voltages, although it is nominally +5V in most systems. The trigger point for Power_Good is about +2.4V, but most systems require the signal voltage to be within the tolerances listed here:

Voltage Ranges for the Power_Good Signal

Power_Good (+5V)3.0V6.0V

Replace the power supply if the voltages you measure are out of these ranges.

Again, it is worth noting that any and all power supply tests and measurements must be made with the power supply properly loaded, which usually means it must be installed in a system and the system must be running.


Uninterruptible Power Supplies (UPS)

Short for uninterruptible power supply, a power supply that includes a battery to maintain power in the event of a power failure. Typically, a UPS keeps a computer running for several minutes after a power failure, enabling you to save data that is in RAM and shut down the computer gracefully. The UPS is also a line conditioner (power stabilizer)Many UPSs now offer a software component that enables you to automate backup and shut down procedures in case there’s a power failure while you’re away from the computer.

In a true UPS system the computer is always operating from the battery, there is no switching circuit. A voltage inverter converts from 12V DC to 220V AC. It is essentially a power system that generates power independently of the AC line. A battery charger connected to the line or wall current keeps the battery charged at a rate equal to or greater than the rate at which power is consumed. When the AC current supplying the battery charger fails, a true UPS continues functioning undisturbed because the battery-charging function is all that is lost. Because the computer was already running on the battery, no switching take place, and no power disruption is possible.

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