BACK  HOME  NEXT

Lesson 8: Phono Plugs and Alligator Clips

Lab 4: Installing Phono plugs

This lab involves preparing a patch cord.

Note: Include your completed patch cord with your Section 1 assignment.

Supplies

• two phono plugs (also called RCA plugs)

• 0.6 m patch cord (two conductor 18-guage stranded wire)
• utility knife
• wire stripper (optional)
• soldering iron and solder (TV or radio solder)
• needle-nose pliers
• metric ruler

Method

Unthread the outer cord end of the phono plug from the main part. Slide the outer cord end of the plug over the patch cord.

Use a utility knife to separate the two conductors of the 0.6 m patch-cord wire. Make the cut in the center of the insulation, between the two conductors. Separate the wires for 15 mm. Be careful not to damage the insulation.
Carefully strip 7 mm-8 mm of the insulation from each conductor of the patch-cord wire. Be very careful to not cut or nick any of the conductor strands. Tightly twist each of the stripped strands. Trim any uneven edges.

3. Why is only 7 mm-8 mm of insulation stripped from the ends of the leads (conductors) when attaching a phono plug?

Compare your responses with the Suggested Answers

Carefully examine the two conductors. One of the conductors (wires) will have a mark, lettering, and/or be a different colour. For instance, the wire strands may be silver colour instead of copper. The insulation may also identify the type of wire, as shown in the following diagram.

Place the stripped end of the marked conductor through the hole in the terminal for the center pin of the phono plug, from the inside forward.

Bend the conductor back along the terminal. Use the needle-nose pliers to press the wire tightly against itself.

Place the stripped end of the other conductor (the unmarked lead) through the hole in the crimp-tab terminal of the phono plug from the inside outward. Bend the wire tightly back along the terminal. The wire should now be positioned so the crimp tab will be around the insulation of this conductor. Do not crimp the tab yet.

Solder the central conductor in the place on the centre-pin terminal.

Note: Take care that you do not heat the components too long as the insulation on the cord and on the phono plug may melt. (Recall the three-second rule!) Refer to Lab 2 for soldering technique. Make sure your iron is HOT! Carefully check to make sure the centre-pin conductor does not touch the crimp-tab conductor.

Next, solder the second (unmarked) conductor in place on the crimp-tab terminal. Again, be careful not to overheat the wire.

Use a pair of pliers to crimp the tab over the insulation of the second (unmarked) conductor. Make sure the cable is firmly held by the crimp tab.

4. What is the purpose of the crimp tab on a phono plug?

Compare your responses with the Suggested Answers

Alligator-Clip Test Leads An alligator-clip test lead is another common type of electrical cable. It consists of one multi-stranded wire with (usually, matching colour) alligator clips on either end (for example, black leads usually have black alligator clips on them; red leads have red clips). Alligator clips are useful for temporarily connecting power supplies or components together. Alligator-clip test leads can be made using fine, multi-stranded wire and attaching the alligator clips. Follow much the same procedure as you used for attaching the lead to the outer tab on the phono plug. Insulated alligator clips have a plastic sleeve that slides over them to help prevent short circuits.

Lab 5: Installing Alligator Clips This lab involves preparing alligator-clip test leads. Note: Include your completed alligator-clip test leads with your Section 1 assignment. Supplies four alligator clips utility knife or wire stripper needle-nose pliers metric ruler soldering iron and solder (TV or radio solder) 1 m of 18-guage stranded lead wire (single-conductor wire) or 0.5 m two conductor wire Method Locate the alligator clips and the red wire in your supply kit. Cut the lead wire into two pieces, each 0.5 m long. Strip the insulation for 7 mm-8 mm from each end. Twist the wire strands firmly. (If there is an insulating sleeve for the clip, slip the sleeve down the lead wire.) Place the stripped end of one conductor through the hole in the base of the alligator clip. Bend the conductor back along the base. Solder the wire and crimp the tab(s) in place. Slide the insulating cover back over the clip. Repeat this procedure with the other three ends of the lead wires. If possible, use the same colour alligator clips on the ends of each conductor. These clips can now be used to connect power to other projects. Include the alligator-clip test leads with your Section 1 assignment for evaluation.

These alligator-clip leads will prove valuable for future activities.

5. Explain why alligator-clip test leads are useful when building electronic projects.

Compare your responses with the Suggested Answers

Banana-Plug Test Leads

A banana-plug or banana-clip test lead is another type of electrical cable. It consists of a single multi-stranded wire with a banana plug or clip on one end and a probe or alligator clip on the other end. Banana plugs are used to connect the test lead to the meter on many multimeters.

Banana-plug leads can be made up if necessary, using a procedure similar to the one used for the phono plugs. Attach the lead wire to the centre-rear part of the banana plug.

If you are making a banana-plug test lead for a multimeter, you may connect a probe or an insulated alligator clip to the other end of the lead wire.