PC-power-supplies.txt					05/12/98

	If your PC is DEAD in the water and you aren't even
	getting BIOS beep codes, one of your problems probably
	is the power supply.

	Get a DC voltmeter (available at any electronics store like
	Radio Shack, etc) and connect a streched out paper clip 
	to the positive leed (Red).  Now connect the ground leed 
	(black) to the shiny metal sheild of the power supply itself.

	Now, turn on the machine and carefully insert the 
	paper-clipped postive leed to each of the wires going to the
	plastic power supply connector on the motherboard.  Verify
	that these voltages are the same as depicted here.  If ANY 
	of the voltages drastically differ from this text, your
	power supply is defective.


	Note:  All power supply voltages vary a little.  Any voltages
		that are +/- 1 volt from what is depicted here should 
                be ok.


	**NOTE**:  If the two power connectors on the motherboard
		   have been SWAPPED (ie.  the black wires are
		   are *NOT* ALL together) then the machine is 
		   realistically toast.  You have probably permanently 
		   damaged the motherboard, the CPU, and possibly 
		   EVERY card and device in the computer as well.
		   Sorry!  Yes.. it IS a stupid design but it was
               fixed with ATX power supplies.
	

	Classic AT-style Motherboard power connector:

                +--+
                |  |    Red    --  +5 volts
                +--+
                |  |    Red    --  +5 volts
                +--+
                |  |    Red    --  +5 Volts
                +--+
                |  |    White  --  -5 Volts
                +--+
                |  |    Black  --  GND (0 volts)
                +--+
                |  |    Black  --  GND (0 volts)
                +--+
                |  |    Black  --  GND (0 volts)
                +--+
                |  |    Black  --  GND (0 volts)
                +--+
                |  |    Blue   --  -12 Volts
                +--+
                |  |    Yellow --  +12 Volts
                +--+
                |  |    Red    --  +5 Volts
                +--+
                |  |    Orange --  +5 Volts (power good signal)
                +--+

	ATX Power supply Style:

		Thanks to billho@pacific.net.sg for this one:

		Orange +3.3V 11	|o||  1 Orange  +3.3V
		Blue    -12V 12	|o|o|  2 Orange  +3.3V
		Black    GND 13	|o|o|  3 Black   GND
		Green  PS-ON 14	|o|o|  4 Red     +5V
		Black    GND 15	|o|o|  5 Black   GND
		Black    GND 16	|o|o|  6 Red     +5V
		Black    GND 17	|o|o|  7 Black   GND
		White    -5V 18	|o|o|  8 Gray    PS-OK
		Red      +5V 19	|o|o|  9 Purple  +5V Stand-By
		Red      +5V 20	|o|o| 10 Yellow  +12V



	PC Device power connector:

            +----------------+
           /  O   O   O   O   \
          +--------------------+
              
    Yellow    |   |   |   |     Red
   +12 volt --+   |   |   +-- +5 Volt
                  |   |
       Black      |   |     Black
    GND (0 Volt) -+   +- GND (0 Volt)
         



--	Written by David Ranch (dranch@ecst.csuchico.edu)