Chapter 19. Ten Circuit First-Aid Techniques and Supplies

Circuitbuilding skills come in extra handy when you can apply them on the spot to make repairs or rescue a broken gadget. You'll have to be prepared, though, and that's what this chapter is all about. By assembling an electronics first-aid kit, you'll be ready to tackle a lot of the "Murphy bites" that seem to occur at the most inopportune times.

Common Replacement Transistors and ICs

Somewhere in your toolbox, keep a small plastic box with a selection of common transistors and ICs. Many circuits can be made to work, although possibly not at peak performance or under all conditions, with a substitute chip or transistor. Here's a good starter list of handy parts; add more that suit your specialty:

  • Bipolar transistors — 2N3904, 2N3906, TIP41, TIP42;

  • MOSFETs — 2N7000, IRF510;

  • Diodes — 1N4148, 1N4001, 1N4007;

  • Analog ICs — 741, LM324, 7805, 7812, LM386. (Sketch the pin configurations on a piece of paper you keep in the same box.)

Clip Leads

Definitely useful in a pinch, a small bundle of various types of clip leads should be in your tool kit. Have a couple with heavy clips and wire that can handle currents of a few amps. A clip lead with a banana plug on one end can often replace a broken or lost multimeter probe.

Electrical Tape

Every toolbox should have a least one good-sized roll of quality electrical tape, such as Scotch 33+ or 88. Use it to replace heat-shrink tubing in a splice, to insulate a terminal (each layer is rated at 600 V ...

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