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Handy Electronics Youtube Videos

MIT OCW - Fundamentals (and Misc) - Oscilloscopes - Reactive Components - Active Components - WA2KWL (Jonathan Gordon), who is the man: - Microcontrollers - Circuit Troubleshooting - TV Repair: - Just interesting (as in, not necessarily useful): - Totally Irrelevant:


MIT OCW 6.002 Annotations

Fundamentals (and Misc)(Edit) - Oscillation

Radio Wave Production?

Quaint Radio Basics

Wire Antenna Currents


Testing An Electronic Circuit - Making A Circuit Board

Tube Radio Repair Essential Tools

No video for this one, just a tip:

SMD Soldering


Choosing an Oscilloscope (Afromod)

Basic Tutorial (Afromod)

Sine wave vs. Square wave

Reactive Components(Edit)


Electroluminescent Backlight (Or, how to get 100V AC @ 150 Hz from 5V DC)

  • Video starts at 1:14 and ends at 2:00, or just skip straight to their web site
  • Inductors resist change, so if their output is suddenly cut off (as in when the first MOSFET is switched off, controlled by the AVR microcontroller's internal timer), a voltage spike occurs while the inductor "tries to keep the current flowing".
  • When this happens, the monster diode passes the kick-back voltage into the capacitor (I don't fully understand that storage part. Capacitors hold a charge, but how exactly does that relate to a high voltage?). The reverse-bias of the capacitor works as a peak detector.
  • As the other MOSFET oscillates (at a much lower rate, also controlled by the AVR), the negative terminal of the electroluminescent device is pulled low and current flows through it.
  • A higher frequency for the first MOSFET gives less time for the inductor to build its magnetic field, so the resulting voltage spike is smaller.
  • Driven by this C code

All-American 5 Radio---Transformer Basics

  • Current in primary flows opposite the secondary
  • Lowering voltage in primary (or moving the two further apart) causes secondary to flow with primary
  • Factors: # of turns, how wound, gauge of wire
  • Collapsing magnetic field reverses current
  • Cores:
    • Air core: More in high-frequency (such as Radio Frequency)
    • Iron core: More in low-frequency (audio and power). Can transfer much more power
  • Step-down transformer, e.g. AM radio to use high-impedance circuit to drive 8Ω speaker
  • Step-up transformer, higher voltage on secondary (but lower current, of course)
  • Both step-up and step-down
  • At 7:02, he shows two air-cores on an oscilloscope.
  • Side-by-side:
    • Windings in same direction = AC out of phase
    • Windings in opposite directions = AC in phase
  • One inside other
    • Windings same = AC in phase
    • Windings opposite = AC out of phase

Olympic College

  • Fewer turns in the primary means: secondary current less, voltage more
  • Vin * Iin = Vout * Iout (power of both is roughly equal)
  • Vout/Vin = Iout/Iin = Coilsout/Coilsin (mechanical advantage)

How It's Made---Pole Transformer

  • Not terribly informative, but mesmerizing as all industrial manufacturing videos are.


Animated Capacitor Charging @ 2ns, 1ps/frame

Images of Bad Capacitors (e.g., capacitor plague)

  • I had a motherboard that had this problem

Scope of Bad Capacitor (info in comments)

My favorite High-voltage Cap Guy, bobdavis321

Discharging a DC Filter Capacitor (wa2kwl)

  • Had bleeder resistor, removed.
  • Then he pops it with a screwdriver.
  • I guess he's just showing what caps charged to 170V can do.

Active Components(Edit)

Very Cursory Presentation

Testing Transistors by a Very Fast Japanese Guy

Haltingly Presented Analysis Prep and, Common-Emitter Analysis

Biasing an Audio Transistor (AllAmerican5Radio)



iPod Amp from Salvaged TV Parts

  • TDA2616Q + 2A regulated 6V DC PS + Speakers + Tupperware

Op Amp primer (by sounddoctorin)

  • "Op" = Performs mathematical operations
  • Comparator: Compares two inputs, inverting (+) and non-inverting (-) to output (will go very high if + is greater, very low if - is greater), plus voltage rail
  • Can hook up voltage follower (output to non-inverting side)

From IRC: <hjohnson> a) there is a virtual short circuit between the + and - terminals (ie the voltage difference between them, assuming a feedback resistor, is zero) and they are also a virtual open circuit (ie, no current goes through it). Using that and KVL/KCL, you can solve almost any op-amp circuit.

<Shpook> hmmm....I'd suggest a book called "op-amps for everyone"

Op Amp Design Basics - Non-Inverting Amplifier - Part 1

  • How to find Vo/Vs:
    • R1/R2 = Voltage Divider
    • Ip (Current @ Vp) = 0, because Vp has infinite impedence
    • Vp = Vs(R2/(R1+R2) {therefore} Vp/Vs = R2/(R1+R2)
    •'s losing me. I don't want to pretend like I understand and keep taking notes.

WA2KWL (Jonathan Gordon), who is the man:(Edit)

User Page

Digital RFI

Tips for troubleshooting a complicated analog circuit on a solderless breadboard

D-type Flip-Flop (computer PSU)

Test for Electrical Circuit Continuity

AC Adapters

LED Semiconductor Physics Made Easy

Ethernet 10Base-T Manchester Encoded Signaling

Parallel ATA Hard Drive Oscilloscope Signals

DSL Broadband Modem Oscilloscope Signals

AC Copper Wiring vs MotherBoard Copper Trace

Harmonic Freq Period Wavelength
1st 166 MHz 6 ns 0.904m (36")
3rd 498 MHz 2 ns 0.301m (12")
5th 830 MHz 1.2 ns 0.181m (7.2")
7th 1.162 GHz 0.9 ns 0.129m (5.4")

Power Factor

Device Behavior E-I Relation Power Curve Power Factor (efficiency)
Light bulb Simple resistor In-phase Also in-phase, device dissipates True Power .9-1
Switched-Mode PSUs, Diode Rectifiers, TRIAC dimmers Creates wasteful harmonic currents In-Phase .5-.8
Motor Very inductive E leads I ("ELI the ICE man") Alternates as magnetic field expands/collapses .4-.7

Computer PSU

Yellow 12V
Red 5V
Orange 3.3V
Black Gnd

Cable TV Signal


L293 Dual H bridge Motor driver IC

Circuit Troubleshooting(Edit)

TV Repair:(Edit)

Dave's TV in Grants Pass, OR

Then there's John from Preher-Tech, who moves faster and zips past more details (though he does drop more advertisements):

Just interesting (as in, not necessarily useful):(Edit)

Totally Irrelevant:(Edit)

Last changed: 2010/11/02 18:31