Oscilloscope vs Multimeter for PCB Repair Malaysia – When Do You Need FNIRSI DSO-152 Plus?

You have a faulty PCB.

The power supply appears normal.

The fuse is good.

There is no obvious burnt component.

But the circuit still does not work.

Should you continue troubleshooting with a digital multimeter, or is it time to use an oscilloscope?

For electronics repair, these two instruments perform different jobs.

A multimeter is excellent for checking:

Voltage

Resistance

Continuity

Current where appropriate

An oscilloscope such as the FNIRSI DSO-152 Plus allows you to see:

How a voltage changes over time

This makes it useful for suitable:

PWM signals

Pulse signals

Sensor outputs

Audio signals

Oscillator circuits

Control signals

Power supply ripple

The best repair approach is usually not:

Multimeter OR oscilloscope

but:

Multimeter first → Oscilloscope when waveform information is needed

What Does a Multimeter Tell You?

A digital multimeter normally provides a numerical measurement.

For example:

5.02 V

This is very useful.

If a circuit requires a 5 V supply, the multimeter quickly tells you whether approximately 5 V is present.

But that number does not always tell the complete story.

What Does an Oscilloscope Tell You?

An oscilloscope displays voltage against time.

Instead of seeing only:

5.02 V

you may see whether that voltage is:

Stable

Noisy

Pulsing

Dropping intermittently

Containing ripple

This additional information can be important when repairing electronics.

Example: Multimeter Shows 5 V but PCB Keeps Resetting

Suppose a microcontroller PCB keeps restarting.

You measure the supply with a multimeter:

5.0 V

Everything appears normal.

But the reset occurs only for a very short moment.

The multimeter may not make the brief disturbance obvious.

An oscilloscope may help reveal a temporary:

Voltage dip

Noise event

Ripple increase

or other transient behaviour.

This Does Not Mean the Multimeter Is Wrong

The multimeter and oscilloscope are simply showing different information.

The multimeter may provide a useful numerical value.

The oscilloscope shows how that signal behaves over time.

Both can be correct.

Start PCB Repair with the Multimeter

For many repairs, the multimeter should still be one of the first tools you use.

Before searching for waveforms, check basics such as:

Fuse

Input voltage

Power rails

Short circuits

Ground continuity

Connectors

Switches

Obvious component faults

There is little value searching for a PWM signal if the controller has no power.

When Should You Move to an Oscilloscope?

Once the basic DC conditions appear correct, you may need to ask:

Is the circuit actually operating?

For example:

Is PWM being generated?

Is the oscillator running?

Is the sensor producing pulses?

Is an audio signal reaching the amplifier?

Is a control signal reaching the driver?

These are oscilloscope questions.

Example: Motor Does Not Run

Suppose a PCB controls a DC motor.

With a multimeter, you may check:

Controller supply

Motor supply

Continuity

Connector

But if those are correct, the next question may be:

Is the controller generating PWM?

This is where an oscilloscope becomes useful.

PWM Present but Motor Still Does Not Run

Suppose you find PWM at the microcontroller output.

Now trace the signal.

Check whether it reaches:

Driver input

If PWM exists at the MCU but disappears before the driver, investigate the circuit between those points.

Possible causes include:

Resistor

Buffer

Optocoupler

Logic IC

Connector

Broken PCB track

The oscilloscope helps identify where the signal disappears.

Example: Fan Does Not Change Speed

A multimeter may confirm that the fan has power.

But if the system uses PWM speed control, the oscilloscope can help determine whether:

PWM is present

and

Duty cycle changes when speed is adjusted

If the command changes correctly but the fan does not respond, the investigation moves elsewhere.

Example: Sensor Has Power but No Reading

Suppose a sensor receives the correct supply voltage.

The multimeter confirms:

Power = Good

But the controller reports no sensor reading.

Now determine what type of output the sensor should produce.

If it produces:

Pulse

PWM

or a changing analogue signal,

an oscilloscope may help reveal whether the sensor output actually changes.

Sensor Output Is Good but Controller Still Shows Error

Trace the signal from:

Sensor

to

Connector

to

Signal-conditioning circuit

to

Controller input

The problem may be the wiring or PCB rather than the sensor.

Example: Audio Amplifier Has No Sound

A multimeter can check:

Supply voltage

Speaker continuity where appropriate

Basic DC conditions

But it cannot easily show you an audio waveform moving through the circuit.

With an oscilloscope and a suitable test signal, you can trace:

Input

→ Pre-amplifier stage

→ Signal-processing stage

→ Amplifier stage

If the signal disappears after a particular stage, you have narrowed the fault location.

Example: PCB Has Power but No Output

This is a common repair situation.

The multimeter confirms that the main rails are present.

Now use the oscilloscope to investigate suitable signals such as:

Control pulses

PWM

Low-frequency oscillators

Sensor activity

Audio

Enable signals

The exact test points depend on the circuit.

Voltage Present Does Not Mean Circuit Is Working

This is one of the most important lessons in electronics repair.

A PCB can have:

Correct input voltage

Correct regulator output

and still fail completely.

Why?

Because the circuit also needs the correct:

Timing

Control

Signal

Enable

Communication

and other operating conditions.

The multimeter confirms power.

The oscilloscope helps investigate activity.

What Is Signal Tracing?

Signal tracing means following a known or expected waveform through different circuit stages.

For example:

Signal source

→ Resistor

→ Buffer

→ Driver

→ Output

Measure each suitable point.

If the signal exists before a component but disappears after it, that area deserves further investigation.

Signal Tracing Is Not Random Probing

Before measuring, understand:

What signal should exist?

Where should it go?

What voltage should it have?

What frequency should it have?

A schematic or working PCB can make signal tracing much more effective.

Working PCB vs Faulty PCB

If you have an identical working board, troubleshooting becomes easier.

Measure the same test points on:

Good PCB

and

Faulty PCB

Compare:

DC voltage

Waveform

Frequency

Duty cycle

Signal presence

This can quickly reveal where the two boards behave differently.

Example: Good PCB Has Pulses, Faulty PCB Is Flat

Suppose the same test point shows:

Good PCB = Repetitive pulse

Faulty PCB = Flat line

Now you have a strong clue.

Move backward through the signal path until you find the stage where the difference begins.

Multimeter Is Better for Some Jobs

Do not use an oscilloscope simply because it looks more advanced.

A multimeter is generally much more convenient for:

Resistance

Continuity

Diode checks

Static DC voltage

Basic current measurement

Use the correct tool for the measurement.

Oscilloscope Is Better for Changing Signals

Use an oscilloscope when the important information involves:

Time

For example:

Frequency

Pulse width

Duty cycle

Ripple

Noise

Intermittent drop

Waveform shape

Startup behaviour

These are difficult to understand from one static number.

Can DSO-152 Plus Replace a Multimeter?

No.

The FNIRSI DSO-152 Plus should not be considered a replacement for a good digital multimeter.

For PCB repair, the two instruments complement each other.

A practical technician may use:

Multimeter → Oscilloscope → Other specialised instruments when required

Is DSO-152 Plus Enough for PCB Repair?

It depends on the PCB.

The DSO-152 Plus is an entry-level mini oscilloscope with approximately 200 kHz bandwidth and 2.5 MS/s sampling.

It can be useful for suitable lower-frequency troubleshooting such as:

Basic PWM

555 timer circuits

Low-frequency pulses

Suitable sensor outputs

Basic audio signals

Simple educational electronics

But it is not suitable for every PCB.

What Type of PCB May Need a Better Oscilloscope?

A higher-performance instrument may be required for:

High-speed digital electronics

Multi-megahertz clocks

Fast communication buses

High-frequency switching circuits

Detailed SMPS analysis

Advanced automotive electronics

Professional signal-integrity work

Multiple signals that must be compared simultaneously

Choose the oscilloscope according to the circuit.

Why Bandwidth Matters in PCB Repair

Suppose a PCB uses a:

16 MHz clock

A 200 kHz-class oscilloscope is not the correct instrument for accurately analysing that clock waveform.

The fact that the PCB itself is small or low voltage does not mean its signals are slow.

Always check the expected signal frequency.

Sampling Rate Matters Too

A digital oscilloscope takes samples of the waveform.

If the signal is too fast relative to the measurement system, the display can become misleading.

You may see:

Wrong waveform

Wrong apparent frequency

Missing pulses

Aliasing

Therefore:

Seeing a waveform does not automatically mean the measurement is accurate.

Single Channel vs Dual Channel for Repair

The DSO-152 Plus is useful when you need to inspect one suitable signal at a time.

But some troubleshooting tasks benefit greatly from comparing two signals simultaneously.

For example:

Input vs output

PWM vs feedback

Clock vs data

Two amplifier stages

In those situations, a dual-channel oscilloscope may be more useful.

What About UART, I2C and SPI?

The DSO-152 Plus may help confirm basic electrical activity on suitable signals.

For example:

Is UART TX active?

Is an I2C line stuck?

Is there SPI clock activity?

But if you need actual protocol decoding, a suitable logic analyzer or more advanced test instrument may be better.

What About Power Supply Ripple?

An oscilloscope can be useful for observing suitable low-voltage power rail ripple.

For example, a circuit may have approximately the correct DC voltage but excessive ripple.

However, measuring ripple correctly requires:

Proper probe technique

Suitable settings

Understanding of the circuit

Do not casually probe hazardous mains or SMPS primary circuitry.

What About Intermittent Faults?

This is another area where an oscilloscope can help.

Suppose a PCB fails only when:

Motor starts

Relay activates

Load increases

Connector moves

Equipment warms up

You may observe whether a suitable signal changes at the same moment.

This can reveal faults that are difficult to catch with a static measurement.

Example: PCB Resets When Relay Activates

The multimeter may show a normal supply most of the time.

Use the oscilloscope to observe the low-voltage supply while the relay activates.

If a brief voltage disturbance coincides with the reset, you now have useful troubleshooting evidence.

Don't Replace Components Before Measuring

A common repair approach is:

No output → Replace IC

If that does not work:

Replace another IC

This can waste time and create additional problems.

A better process is:

Check power

→ Check operating conditions

→ Check input signal

→ Check output signal

→ Trace where the behaviour changes

Measurement should guide component replacement.

Don't Assume the Main IC Is Faulty

A controller may fail to operate because of:

Missing power

Reset condition

Missing clock

Enable signal

Faulty peripheral

Shorted communication line

Power instability

The main IC may be perfectly good.

Multimeter First, Oscilloscope Second

For many PCB repairs, this is a practical sequence:

Step 1 – Visual inspection

Look for:

Burnt components

Broken connectors

Corrosion

Cracked solder joints

Damaged tracks

Step 2 – Multimeter

Check:

Short circuits

Continuity

Input voltage

Power rails

Basic components

Step 3 – Oscilloscope

Check:

PWM

Pulse signals

Oscillator activity

Sensor outputs

Audio

Ripple

Intermittent behaviour

Step 4 – Specialised Tools

Use when necessary:

Logic analyzer

LCR meter

Component tester

Signal generator

Higher-bandwidth oscilloscope

Thermal camera

The exact workflow depends on the PCB.

DSO-152 Plus as a Secondary Oscilloscope

Even a repair shop with a larger bench oscilloscope may find a compact mini oscilloscope useful for certain basic checks.

Possible uses include:

Quick waveform confirmation

Training

Portable troubleshooting

Low-frequency circuit checks

Educational demonstrations

But it should not be expected to replace a professional bench oscilloscope.

Good Choice for Beginners?

For someone learning electronics repair, the DSO-152 Plus can provide a simple introduction to:

Waveforms

Frequency

Duty cycle

Triggering

Signal tracing

Basic troubleshooting

This can help users move beyond simply measuring DC voltage.

When Should a Beginner Upgrade?

Consider upgrading when you repeatedly encounter:

Signals above the instrument's bandwidth

Need for two channels

Fast digital circuits

Advanced SMPS troubleshooting

Detailed waveform analysis

Professional electronics development

At that point, a higher-performance oscilloscope becomes more practical.

Quick PCB Repair Tool Guide

Use a multimeter when you need to know:

Is voltage present?

Is there continuity?

What is the resistance?

Use an oscilloscope when you need to know:

Is the signal changing?

What does the waveform look like?

What is the frequency?

Is PWM present?

Is the power rail stable over time?

Use a logic analyzer when you need to know:

What digital data is being communicated?

Different questions require different instruments.

Safety During PCB Repair

A PCB may contain both:

Low-voltage electronics

and

Hazardous voltages

on the same board.

Be especially careful with:

AC mains

SMPS primary sections

Inverters

High-voltage capacitors

Motor drives

Unknown industrial equipment

Do not assume battery operation or a compact oscilloscope automatically makes a hazardous measurement safe.

Understand the circuit, reference and voltage before connecting the probe.

Oscilloscope vs Multimeter for PCB Repair Malaysia

For electronics repair, the multimeter and oscilloscope should not be treated as competing tools.

The multimeter answers questions such as:

“Is 5 V present?”

The oscilloscope answers questions such as:

“What is that 5 V doing over time?”

For suitable lower-frequency electronics, the FNIRSI DSO-152 Plus can provide an affordable and portable way to start learning waveform-based troubleshooting.

It can be particularly useful for:

Students

DIY electronics users

Arduino projects

Basic PCB repair

PWM troubleshooting

Sensor testing

555 timer circuits

Low-frequency signal tracing

MTM Precision supplies FNIRSI oscilloscopes, multimeters and electronic test instruments in Malaysia.

If you are repairing a PCB and are unsure which test instrument is suitable, send us:

A photo of the PCB

Equipment model

Power supply voltage

Description of the fault

Expected signal or frequency if known

Photo or video of your existing measurement

through WhatsApp.

We can help determine whether you need the FNIRSI DSO-152 Plus, a multimeter, a higher-performance oscilloscope, logic analyzer or another test instrument.

MTM Precision Sdn Bhd

Showroom & Service Centre:
No. 29-1 & 2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.

Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my

Supplying FNIRSI and electronic test instruments throughout Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kelantan, Terengganu, Kedah, Perlis, Sabah and Sarawak.