How to Test a Circuit Board

Key Takeaways

• Testing a circuit board starts with visual inspection and multimeter checks, progressing to more advanced diagnostic techniques for complex issues.

• Simulation tools like PSpice help catch faults early through analyses like DC Sweep, Transient, and Monte Carlo before physical boards are ever built.

• OrCAD X enhances circuit board testing with built-in features like signal integrity analysis and design rule checks.

Diagnosing and troubleshooting electronic circuits requires a blend of confidence, skill, and the right tools. When a circuit board isn't performing as expected, systematically testing and debugging is the only way to identify faults.

While physical testing is essential, modern design tools like OrCAD X and PSpice simulation software let you test your designs before they ever hit the manufacturing floor. We'll first walk through the traditional methods of physical circuit board testing, then explore how simulation tools and specifically PSpice offer a powerful alternative to those methods. Let's look at how to test a circuit board, both in the real world and in the digital realm.

Tools for Circuit Board Testing

Before you start probing around, make sure you have these basic tools handy:

• Analog/Digital Multimeter: A must-have for measuring voltage, current,  resistance, and testing continuity.

• Soldering Gun: For repairing broken connections and replacing components.

• Desoldering Station: To safely remove components without damaging the board.

• Magnifying Glass: Helps you spot tiny defects like cracked solder joints or broken traces.

These are your first line of defense against common problems like short circuits, broken traces, or faulty components. But you can go further during the design phase to ensure your designs are robust.

How to Test a Circuit Board for Failures

When a circuit board stops functioning, it’s rarely random—most failures stem from a handful of well-known culprits. To effectively troubleshoot, follow a structured workflow that not only inspects the board visually but also probes specific failure-prone areas using precise tests.

Step 1: Perform a Visual and Thermal Inspection

Use a magnifying glass or microscope to inspect the board for:

• Burnt or discolored components, especially around power circuits, typically a sign of overcurrent or overheating.

• Cracked or bulging capacitors, electrolytic capacitors are especially prone to failure due to aging or ripple current stress.

• Lifted or broken PCB traces, often caused by overheating or physical stress.

• Cold solder joints (dull, cracked, or inconsistent solder), frequently responsible for intermittent issues.

• Corrosion around pins or connectors, often from moisture ingress or flux residue.

Then, power up the board briefly and use an infrared thermometer or your hand (carefully) to detect:

• Hot ICs or regulators, which may indicate shorts or overloading.

• Cold spots in circuits that should be active, often a sign of an open circuit or dead driver.

Step 2: Check the Power Rails

Use a digital multimeter (DMM) to measure voltages at key nodes:

• Measure voltage at voltage regulators’ input and output. Common issues include:

• Input voltage missing = blown fuse, open circuit, or faulty input connector.

• Output voltage low or zero = shorted load, failed regulator, or incorrect feedback resistor.

• If the regulator is a switching type, use an oscilloscope to verify switching activity and output ripple, excessive ripple often means a failed output capacitor or poor layout.

Check for:

• Shorted power rails (measure resistance from rail to ground), a very low value (e.g., <10Ω) suggests a shorted IC or capacitor.

• High dropout across a linear regulator, it could indicate excessive current draw or bad regulator.

Step 3: Validate Oscillators and Clock Signals

Use an oscilloscope to check:

• Main crystal oscillators or external clock sources—absence of waveform means the microcontroller or clock IC won’t boot.

• PLL or frequency synthesizers—verify correct output frequencies if your design uses them.

Common issue:

• No clock = the microcontroller may appear dead, even though power is present.
  
  

Step 4: Probe Input/Output Interfaces

I/O failures can be subtle but impactful. Check:

• Voltage levels at digital I/O pins when idle and active.

• Stuck high or low = possible damaged GPIO, failed buffer, or short to power/ground.

• Pull-up/pull-down resistors: verify presence and correct value; missing or wrong value resistors can cause logic errors.

• If inputs are protected with TVS diodes, Zener diodes, or series resistors, test for shorts or open connections.

Test case:

• Sensor line always reads “1”? = input pin may be floating, or pull-down is missing.
  
  

Step 5: Inspect Communication Interfaces

For protocols like I²C, SPI, UART, RS-485, or Ethernet, use a logic analyzer or oscilloscope to capture traffic:

• I²C: Check for proper START/STOP conditions, ACK/NACK, and that SDA/SCL lines aren’t stuck.

• SPI: Verify clock (SCLK) toggles, correct chip select (CS) behavior, and valid data.

• UART: Look for baud rate mismatches, framing errors, or signal inversion.

• RS-485/Ethernet: Check transceiver enable pins and termination resistors.

Common failures:

• Damaged transceivers from ESD or overvoltage.

• Improper termination causing reflections and data corruption.

• Pull-up resistors missing on open-drain lines like I²C.

How To Verify a Circuit Board Design With Simulation Software

Now, what if you could catch many of these issues before they ever made it to a physical board? No need for the “how to test a circuit board” search. That's the power of simulation. Simulation software allows you to create a virtual model of your circuit and analyze its behavior under various conditions before any manufacturing is completed.

SPICE (Simulation Program with Integrated Circuit Emphasis) is the industry-standard simulation language, and PSpice is Cadence's implementation of SPICE. Types of simulation possible to be conducted using PSpice include:

PSpice Analysis Functionality

How To Validate a Digital Twin with OrCAD X 

OrCAD X offers tools for how to test a circuit board –more specifically a digital twin that you can use to compare to the actual circuit board, through signal integrity analysis and design rule checks (DRCs).

Signal Integrity Analysis with OrCAD X

Signal integrity refers to the quality of the electrical signals in a circuit. As signal speeds increase, signal integrity becomes increasingly important. Use signal integrity analysis for the following: 

• High-Speed Digital Circuits: Any circuit with fast clock speeds, memory interfaces (DDR, etc.), or high-speed serial communication (USB, PCIe, Ethernet) needs signal integrity analysis.

• Long Traces: When signal traces are long relative to the signal wavelength, transmission line effects become significant.

• Critical Signals: Apply to any signal path where timing or signal quality is paramount for proper system function.

By simulating and analyzing signal integrity, you're essentially performing a virtual test of your circuit board before it's even built. This allows you to identify and correct potential signal quality problems that could lead to functional failures or reliability issues. Some of the reasons to implement signal integrity analysis into your workflow:

• Reduced EMI: Proper termination and routing can minimize electromagnetic interference, helping you pass compliance testing.

• Improved Signal Quality: Ensures signals arrive with sufficient amplitude and sharpness, reducing the likelihood of errors.

• Fewer Reworks: Identifying and fixing signal integrity problems early prevents costly board re-spins.

Design Rule Checks with OrCAD X

DRCs work by comparing your design against a set of predefined rules. If your design violates any of these rules, the DRC tool will flag the error and provide you with a description of the problem. Here are some common DRCs:

• Spacing Checks: These checks ensure that traces, pads, and components are spaced far enough apart to prevent shorts and other manufacturing defects.

• Clearance Checks: These checks verify that there is sufficient clearance between traces and other objects, such as vias and mounting holes.

• Trace Width Checks: These checks ensure that traces are wide enough to carry the required current.

• Via Checks: These checks verify that vias are properly sized and placed to ensure reliable connections between layers.

Running DRCs is like having an automated quality control inspector examine your design before it goes to manufacturing. By catching these errors early, you can avoid manufacturing defects and reduce the time and effort required for physical testing and debugging. In essence, DRCs provide another layer of virtual testing to ensure a more reliable and easily testable circuit board.

Wondering how to test a circuit board efficiently and with fewer headaches? With Cadence OrCAD X platform, engineers can move from physical probing to virtual simulations and design rule enforcement. By using built-in tools like PSpice simulations and DRCs, designers can catch issues like voltage instability, frequency interference, or overheating before a board ever gets fabricated. Ready to eliminate trial-and-error from your prototyping process? Explore the OrCAD X Platform and kickstart your workflow with the OrCAD X Free Trial today.