Common Component Mounting Instructions

Toroid Coils

Toroids

Identifying the toroids becomes simple once you figure out the coding. The toroids are designated using the pattern "T-NN-M". The critical pieces are the "NN", representing the outside diameter of the "donut" in hundredths of an inch, and the "M", representing the type of material used to make the core. Tony uses the following toroids in his kits:

• T30-2 (red)
• T37-2 (red)
• T25-2 (red)
• T25-6 (yellow)
• T30-6 (yellow)

Toroids are used in single-winding coils and multi-winding transformers. In either case, the number of turns must be counted. Any pass through the center of the Toroid is counted as a "turn" (see below).

The winding of a single-winding toroidal inductor is fairly straight-forward. Each turn counts as a turn. The windings should be spaced evenly around the circumfrence of the toroid, ideally leaving about a 15 degree "wedge" between the beginning and ending of the winding. The image below is of a 22 turn coil wound on a toroid.

Occasionally, you may find that there is not enough room on the toroid toplace all of the windings without having to go back and add a layer of winding. Tony Parks suggests that you overlap some turns as you put on windings around the circumference of the core so that all turns are on the core by the time you get back to the start end of the winding. This should have negligible effect on the coil's performance in the radio.

Winding toroidal transformers usually involves 2 to 3 windings on the same core. The most common is a transformer with a single winding (primary or secondary) over which two "bifilar" windings are superimposed (two secondaries or primaries). See the Toroid Winding Hints from the Experts for good tips on how to wind a toroidal transformer.

When you have finished winding, stripping, and tinning the toroidal transformer's windings, you will two leads for each winding. Each lead will come out on a different side of the toroid. For example, consider a three-winding transformer with one primary ("P") and two secondary windings ("S1" and "S2"). It will have a total of six leads, three on one side of the toroid and three on the opposite side:

• The two primary leads, "Pa" and "Pb" ("P" stands for primary; "a" is one side of the toroid, "b" is the opposite side)
• The two leads for the 1st secondary winding, "S1a" and "S1b" ("S1" stands for the 1st secondary winding; "a" is one side of the toroid, "b" is the opposite side)
• The two leads for the 2nd secondary winding, "S2a" and "S2b" ("S2" stands for the 2nd secondary winding; "a" is one side of the toroid, "b" is the opposite side)
• 

To mount the transformer you insert the leads into the holes annotated on the board as "P", "S1", and "S2". The holes may also be annotated as to the "row" ("a" row or "b" row) which corresponds to the leads on the "a" side or the "b" side of the toroid.

the builder should start with the single winding, inserting its two leads into the appropriate holes and then do the same with the first of the two bifilar windings, and finally do the same with the second of the two bifilar windings

After inserting the leads, the builder should pull each lead pair through the holesuntil the transformer is snug to the board. Soldering the leads completes the process.

Binocular Transformers

Binocular cores

• One is the actual winding of the coil. Bino cores can be wound either:
  • with all leads coming out of the same end or
  • with some leads coming out of one end and some coming out of the other.
• All Tony's kits - so far - have used the winding convention where all windings come out of one end of the binocular core, with one turn counted each time the wire goes in one hole and comes out the other, at the same end (see below).
• 
• The other aspect is the correct polarity. That is a little easier, since Tony has designed the boards such that the polarity is pretty well handled for you.
  • The key is to start each winding in the same hole of the bino core and end each winding in the other hole (on the same end of the core).
  • When you finish winding the typical bino transformer with one single wire winding and one bifilar (i.e., twisted pair of wires) wire winding (yielding two windings), you have three wires coming out of each hole on the same end of the core, corresponding to the leads of the three windings.
  • You should carefully strip the insulation from the leads (up to within an eighth of an inck of the core) and tin the leads. Sandpaper can be used to strip the insulation, or you can use an Exacto kinfe toscrape it off. Note that the insulation on the wire Tony provides is Not the heat-strippable type.
  • In most of Tony's kits the core is mounted "standing up" vertically and the windings' lead pairs are inserted into the holes corresponding to the winding.
  • For example, if you wind a transformer with one primary (P) and two secondary windings (S1 and S2), you end up with three leads (Pa, S1a and S2a) coming out of one hole and three leads (Pb, S1b, and S2b) coming out of the other hole.
  • The board layout in the enhanced builders notes will usually have annotations on the six holes (for a common transformer) that indicate the lead pairs for the primary, and each of the 2 secondaries.
  • The builder then needs to match the holes with the appropriate winding leads. This graphic is an example:
  • 
  • T201 (above) has one primary and two secondary windings. When wound, it will have 6 leads in all:
    • two leads (Pa and Pb) and
    • four secondary leads (S1a, S2a, S1b, S2a).
    • 
  • You should use an ohmmeter to identify each winding pair.
  Then slip a 1/8" pice of hookup wire insulation onto the Pa and Pb leads to temporarily provide identification of the primary. Also slip a 1/8" piece of insulation onto the S1a and S1b leads to act as a "spacer for the actual mounting.
  • To mount the core, the builder typically starts with the Primary leads, removing the insulation piece and orienting the core such that (in the above instance):
    • the core hole from which Pa lead exits is aligned with the P hole on the top row of the holes and
    • the core hole from which the Pb lead exits is aligned with the P hole on the bottom row.
  • Then insert those primary leads into their corresponding holes.
  • Then take the first pair of S leads (e.g., S1a and S1b) and similarly align with and insert into the "S1" holes (S1a on the top and S1v on the bottom row of holes in the graphic above).
  • Finally do the same thing with the remaining lead pair (S2a and S2b).
  • Then pull through all of the leads from the bottom of the board to ensure no leads have any loose ends or loops topside and the transformer is nice and snug on the board and the 1/8" spacer
  • Solder all leads and you're ready to test them.
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