Student Testing Audio Circuit in Electronics Laboratory, San Francisco State College

What the person is doing:

This person appears to be:

• Testing or troubleshooting an audio circuit, possibly an amplifier or tuner stage
• He’s using a signal tracing method—a process where audio signals are injected into a circuit and then followed through various stages to check performance or isolate faults
• Wearing monitor headphones, he’s likely listening to the output at various points to detect:
• Signal distortion
• Component failure
• Proper frequency response

          This is a classic bench test/training setup—part of audio electronics education or diagnostic work.

Identified Equipment on the Bench:

1. Headphones

• Used for audio monitoring directly from the test circuit
• This was a common method in analog labs before digital scopes or FFT analyzers

2. Circuit Under Test (foreground, center)

• This open frame component (near his hands) is probably:
• A radio receiver module
• Or a small audio amplifier

          It’s being probed and powered with test leads

3. Tube Tester / Variable Power Supply (left)

• The metal device at the front left with rotary controls and ventilation looks like:
• A tube-based audio generator
• Or a bench power supply providing variable voltages to the test circuit
• It may also house a signal tracer or tone generator

4. Bench Multimeter / VTVM (center back)

• The boxy unit with a meter display is likely a vacuum tube voltmeter (VTVM)—used for high-impedance measurements across audio or radio circuits
• Could be reading:
• Input/output voltage
• Gain
• Signal strength

5. Signal Generator or Modulated Source (center-right)

• A likely audio signal generator—used to inject sine/square waves into the test board
• Helps trace signal flow through the system

6. Patch leads and clips

• Classic banana plug and alligator clip jumpers are routing signals from one instrument to the next
• These allow flexible, repeatable testing setups without hard-wiring

Likely Educational Context:

This image captures a person in a practical electronics lab, engaged in:

• Diagnosing audio circuitry
• Measuring and listening to waveform behavior
• Practicing real-world skills for work in broadcast engineering, radio communications, or consumer electronics repair

Credits: 

Some technical descriptions and historical interpretations were developed with the assistance of ChatGPT, an AI language model by OpenAI.