On May 2005 I built "ternary" power supply (discussed in
russian part of our forum) that converts AC 120V to DC +5V & -5V:
Power supply was built from components bought in
RadioShack stores in 2005 (except 7905 and power cable):
$0.99 - power cable (cut from outlet);
$5.00 - enclosure (approximately);
$10.49 - transformer with 2 secondary 6.3V outputs and max. current 3A;
$1.79 - printed circuit board (only 1 half was used);
$2.99 - silver soldering;
$1.99 - diode bridge with max. current 4A;
$1.99 - vinyl enclosures for holes (only one was used - for power cable hole);
$2.29 - fuse holder for using directly in cable;
$2.49 - four 4A fuses (only one was used);
$2.59 - red and black connectors;
$2.59 - another red and black connectors (only red was used);
$1.59 - 4 spacers and 8 screws;
$1.69 - connectors (5 used);
$1.69 - heatsink;
$1.69 - another heatsink;
$1.59 - voltage regulator 7805 (+5V);
$0.42 - voltage regulator 7905 (-5V, bought on
Jameco);
Wires, capasitors, screws etc. were taken from my storage
Adding NY tax 8.75% and we got price over $50...