The Apple II’s CPU clock has jitter or a glitch. This issue is not new—it has been present since its original design in 1977! Bald Engineer uses an oscilloscope to show how often the glitch occurs and how to correlate that jitter to its source—which is useful when you are not testing 40-year-old devices. The device under test (DUT) in this video is the Mega IIe project. It’s a fully compatible Apple IIe built around the Mega II chip.

Did you know that TTL chips do not output 5 volts? 74LS, 74HC, and 74HCT all have different input and output thresholds. Switching between logic families can be difficult if you are not careful. In this video, learn how different 7400-series logic families compare with input threshold, output voltage, frequency, rise time, and propagation delay.

Check out this TI Application Guide for a great resource on logic families.

The 555 is a very popular chip, and for good reason. It is such a versatile timer. Learn about 555 measurements like how to measure the voltage divider inside the chip and what is going on with the signals in an astable multivibrator (clock) circuit. The key to a 555 circuit is connecting the threshold and trigger pins together. But, until you see the schematic and waveforms it may not be obvious why.

Measuring the effectiveness of a heatsink or the thermal load of a CPU requires thermal test tools. In this episode, learn how an IR Thermometer and a Thermocouple could be used on an electronics workbench. Many multimeters (DMMs) include the ability to measure temperature with a K-type thermocouple. See examples of when each measurement could be used.

Behind the scenes of Thermal Tools Tutorial

Originally intended to use the episode to show how hot the Pi 4 would get. However, by the time I got around to producing it, a new version of Raspbian came out, resolving the temperature issues. To heat up the Pi, I used this toolset from GitHub: XXXXX.

See show notes on element14

A multimeter is the go-to-tool for electronics measurements. Knowing how to use it to measure voltage, current, diodes, and transistors can save time (and frustration) while troubleshooting. In this video, James explains how the multimeter works, so that you can understand them better. After watching, you will gain a solid DMM basics understanding.

Behind the scenes of wbw’s DMM Basics

The first Workbench Wednesdays episode covered a pen-style DMM. Back when we were first developing the show, the intent was to be more of a review show and less of a tutorial show. That episode became a mix of both. So we decided to do a straight-up tutorial on DMM basics. Measuring voltage usually has not tripped up too many people, especially on an auto-ranging meter. The main thing to remember with current is to move the red lead back to the voltage input immediately after making a measurement. I touched on continuity briefly but hope to come back and cover that more in the future.

After watching this episode, I would recommend moving to the bench power supply tutorial. After a DMM, the bench supply is one of the most used tools.

See show notes on element14