If it's a 486, it's probably an AT. AT mobos have a single row of pins in their power connectors, usually with two connectors from the power supply place end to end. ATX have a single power connector from the power supply, but with a double row of pins.
To measure the current on supply lines, connect an ammeter in series with the power line to measure on.
[ 12-15-2001: Message edited by: Rob Withey ]