Internal relay inside the power supply is actuated by the power switch connected to your motherboard. This unit performs just as well as atx power supplies that cost well over $100!. This 350 Watt power supply from is UL Listed and super silent in operating noise. All items in the list are compatible replacements for Bestec ATX0300D5WC Rev B power supplies: The following product(s) are recommended based on the information you provided for Bestec ATX0300D5WC Rev B. Laptop Power Supply Cross Reference Engine.Slim Sata Converter Adapter Power Data Cable.Sheet Metal Hand Nibblers Shear Cutters.Molex IDE to 8 Pin EPS CPU Converter Adapter 24 Pin to Dell 24+16 Pin Converter Adapter.HP Slimline Adapter Small 24 Pin ITX to 20 Pin ATX Converter.HP Slimline Adapter 20 Pin ATX to Small 24 Pin ITX Converter.90 Watt Laptop Power Supply Prudent Way AC90.40 Watt Laptop Power Supply FSP FSP040-1ADF03A.FSP 500W Twins Redundant PS2 Computer Power Supply.500 Watt 1U Power Supply Sparkle SPI500U4BG-ZTG.FSP FSP460-60GLC 460 Watt ATX Power Supply.400 Watt 1U Power Supply Sparkle SPI4001UG.400 Watt Fanless Power Supply FSP ZEN 400.Athena AP-MPS3ATX40 400 Watt ATX Power Supply.Dell Dimension 8100 Power Supply Upgrade.Dell F5114 350 Watt Power Supply Upgrade.300 Watt Fanless Power Supply FSP300-60GNF-R.Compaq 277979-001 Power Supply Replacement.Compaq 244166-001 Power Supply Replacement.Deer DR-150FLEX Power Supply Replacement.NPS-180EB A and NPS-225AB A Power Supply Replacement.MPT-301 ATX-350SD Power Supply Replacement.Athena Apollo 400 Watt Micro ATX Power Supply.300 Watt Micro ATX Power Supply FSP300-60GHS.300 Watt Power Supply FSP250-50NWV Upgrade.300W 80+ TFX Power Supply Sparkle SPI300T8AB.Sparkle SPI300T8HNB 300W TFX Power Supply.300 Watt Micro ATX Power Supply MP4ATX30.300 Watt Flex ATX Power Supply SPI300F4BB.270 Watt Flex ATX Power Supply FSP270-60LE.Athena AP-MFATX25 250 Watt Flex ATX Power Supply.FSP FSP250-60LG 250 Watt Flex ATX Power Supply.R8038 Dell Optiplex R8038 Power Supply Upgrade.

N1238 Dell Optiplex Power Supply Upgrade.

200 Watt Flex ATX Power Supply for Shuttle.

200 Watt Flex ATX Power Supply FSP200-50PLA.

180 Watt Gateway Power Supply for Nin Chassis.

1N405 Dell Dimension Power Supply Upgrade.

Dell Optiplex Power Supply 160 Watt P2721.

Dell Optiplex GX150 Power Supply Upgrade.

120 Watt Fanless Flex ATX Power Supply FSP120-50GNF.

90 Watt Flex ATX Power Supply FSP090-50PL.

Bestec atx0300d5wc power supply open