The Alegro 3955B Micro-step stepper driver

    Micro-step driver parts list

 (2) 74LS244 
 (2) 74LS373
(11) 4N35
 (4) Allegro A3955SB
(16) D1 - 1 amp, Schottky, 50 PIV

 R1 - 390 - 470
 R2 - 680
 R3 - 30k
R10 - 10k trimpot
R11 - 10k
R12 - 470
R20 - 10k trimpot
R21 - 7.2k
R22 - 2.2k
Rs - 0.5 1w 
All resisters 1/8w, except for Rs which is 1/2w or 1w

C1 - .05uf to .22uf
C2 - 47uf 50vdc, larger if possible
C3 - 470pf to 1200pf
C4 - 1uf to 10uf