Handy Electronics Youtube Videos

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Static checks before live checks.
Check +V
Check all ground locations
That's all (it's a short video. Notable bonus is the way the text twiddles in at the start. Obskur4tionz Styl3.)

Run wires as short and parallel to each other as possible.
Color-code wires
Keep component leads far enough apart that they don't short
Try to avoid going over the top of ICs
Be aware of adjacent rows' stray capacitance
Diagnose in stages (!) Either one at a time in sequence, or BinaryChop Debugging

Doesn't like mini phono plugs (because they can short during insertion), does like barrel plugs (which don't)
Set MM to continuity, place one lead on plug and the other on the opposite wire termination, then hold them and move the wires around at different angles to test for intermittent connection
To find ground, connect one lead on the shielding of a serial port terminal, then probe using other lead. Anywhere on the circuit you get a beep is a ground connection.
Also, continuity testing fuses (out of or in-circuit)

AC-to-AC Unregulated: Just a transformer; measures higher without load than with.
AC-to-DC Unregulated: Transformer, bridge rectifier; measures higher without load than with.
AC-to-DC Regulated: Transformer, rectifier, filter caps, voltage regulator.
AC-to-DC Switcher: Bridge rectifier, HV filter cap., stepdown transformer, pulse width modulator, switching transistor, rectifier diode; Probably lighter than the transformer version.

Valence shell <-> Band Gap <-> Conduction band
Energy required to move from valence to conduction band defines insulation/conduction. Home run hit vs. Cannon vs. Thump.
Silicon doping:

Silicon has 4 valence electrons, creates strongly bound electrons
Boron, aluminum, gallium = 3 valence electrons; dope with these and you have one electron "missing", hence P-type
Nitrogen, Phosphorous, Arsenic = 5 valence electrons; opposite: N-type

Electrons going from N-type to P-type gives off energy: different wavelengths for different band gaps
Doping with other substrates gives different band gaps, e.g., Gallium Arsenic, Aluminum Gallium Arsenide (=Red: 620-780nm), Aluminum Gallium Phosphorous (=Green: 490-570nm)
Wikipedia elaborates (http://en.wikipedia.org/wiki/Band_gap)

Gap is measured in Volts.
The reverse: "the band gap determines what portion of the solar spectrum a photovoltaic cell absorbs."

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