Item  Description
[1]  Core: PC40EE25-Z, TDK or equivalent Gapped for AL of 335 nH/T2
[2]  Bobbin: EE25, Vertical, 10 pin – Yih-Hwa part # YW-360-02B
[3]  Magnet Wire: #30 AWG
[4]  Magnet Wire: #26 AWG
[5]  Triple Insulated Wire: #26 AWG.
[6]  Tape: 3M # 44 Polyester web. 2.0 mm wide
[7]  Tape: 3M 1298 Polyester Film, 2.0 mils thick, 8.6 mm wide
[8]  Tape: 3M 1298 Polyester Film, 2.0 mils thick, 10.7 mm wide
[9]  Tape: 3M 1298 Polyester Film, 2.0 mils thick, 4.0 mm wide
[10]  Varnish (applied by dipping only, not vacuum impregnation)

1.Bobbin Set Up
Orientation
Set up the bobbin with its pins oriented to the left hand side.
2.Margin Tape
Apply 2.0 mm margin at the pin side of bobbin using item [6]. Match combined height of shield, primary, and bias windings.
3.WD1 Cancellation Winding
Start at Pin 1. Wind 14 bifilar turns of item [3]from left to right. Wind with tight tension across entire bobbin evenly. Cut the ends of the bifilar and
leave floating.
4.Insulation
1 Layer of tape [7] for insulation.
5.WD#2 Primary winding
Start at pin 3. Wind 28 turns of item [3] from left to right. Apply 1 Layer of tape [7] for insulation. Wind another 28 turns from right to left. Wind with
tight tension across entire bobbin evenly. Finish at Pin 1.
6. WD #3 Bias Winding
Start at Pin 4, wind 6 trifilar turns of item [5]. Wind from left to right with tight tension. Wind uniformly, in a single layer across entire width of
bobbin. Finish on Pin 2.
7.WD #4 Bias Winding
Start at Pin 2, wind 6 trifilar turns of item [5] from left to right with tight tension. Wind uniformly, in a single layer across entire width of bobbin. Finish on Pin 5.
8.Insulation
1 Layer of tape [8] for insulation.
Margin Tape Apply 2.0 mm margin at the pin side of bobbin using item [6]. Match
combined height of secondary windings.
9.WD #5 Secondary Winding
Start at Pin 8, wind 7 turns of item [5] from left to right. Wind uniformly, in a single layer across entire bobbin evenly. Finish on Pin 6.
10.Outer Insulation
  3 Layers of tape [8] for insulation.
11.Core Assembly
Assemble and secure core halves using item [1] and item [9]
12.Varnish
  Dip varnish using item [10] (do not vacuum impregnate)