Multi-purpose GM328A transistor tester


Multi-functional transistor tester for automatic detection of NPN and PNP transistors, FET, diodes, dual diode, thyristor, SCR, automatic identification of the transistor pin out. It also can be used as a square signal and PWM signal generator.

Got digital screen for clear readings, small size, can be your all in one electronics component tester. Get it delivered to your door steps fast with nice packing.

Availability: In stock

Yaman Electronics

GM328A transistor tester

Multi-functional transistor tester is designed for the automatic detection of NPN and PNP transistors, FET, diodes, dual diode, thyristor, SCR, automatic identification of the transistor pinout. It is not limited to just transistor testing, it can be your all in one electronics components tester as well.

Besides component tester, this guy has got something special for you. It has pulse width modulation feature, shortly PWM. It also can be used as a square signal and a PWM signal generator.

gm328a features

How to use GM328A?

The working of GM328A is simple just like the other transistor testers. Follow the following two easy steps and get your required results in seconds.

Step 1:

Plugin the power jack to power up the device. If you don’t have power jack, you can also use 9v battery. To use the battery you have to solder the connecting extra to the tester PCB.

The tester can be be powered with 6.8V – 12V DC. This can be achieve by a 9V layer-built battery. Two 3.7V lithium-ion battery in series or AC adapter. When powered on, the current is about 30mA at DC 9V.


Transistor Tester is controlled by a “rotary pulse encoder with switch” (RPEWS). There are 3 modes of operation –

  • Short press the knob
  • Long press
  • Left and right turning of the knob

Short press will switch on the tester and start a test. It will turn off automatically at the end of the test. Long press and left or right turn will activate the function menu. Use > to select items. Press and hold the knob to exit the function menu.

The transistor has 3 test points, TP1, TP2, and TP3, within the test socket. To the right of the test socket is the SMT test pad with identifying numbers.

gm328a transister tester review

Step 2:

Place the component you want to test. It automatically detects the component and displays the results on the LCD screen. It works fine with every component.

But if you are going to test capacitor, please make sure that the capacitor is fully discharged. In another case, if you placed a charged capacitor, you may blow up your gm328a tester.

Self test and calibration of gm328a transistor tester

The self test can be prepared by connecting all three test point together and pushing the RPEWS. To begin the self test, the RPEWS must be pressed again within 2 seconds. The tester with prompt you for the next step.

Wait until the prompt says “isolate probes” and then disconnect the test points. Tester will soon display “1-||-3 > 100nf”. A capacitor with any capacity between 100nF and 20µF connected to pin 1 and pin 3 is required for the last task of calibration.

You should connect the capacitor, after this text is shown. With this capacitor, the offset voltage of the analog comparator will be compensated for better measurement of capacity values.

This test is carried out if you have doubt on calibration, else the gm328a transistor tester comes calibrated.

Components with problems

You should keep in mind by interpreting the measurement results, that the circuit of the transistor tester is designed for small signal semiconductors. In normal measurement condition the measurement current can only reach about 6 mA.

The tester often cannot deliver enough ignition current or holding current for power thyristors or triacs. So a thyristor can be detected as NPN transistor or diode or detected as unknown.

Bonus tips

  • Normally the tester shows the battery voltage with every start. If the voltage fall below a limit, a warning is shown. If you use a rechargeable 9V battery, you should replace the battery as soon as possible or you should
  • If you try to measure little resistor values, you should keep the resistance of plug connectors and cables in mind. The quality and condition of plug connectors are important, also the resistance of cables used for measurement.
  • The same is inforce for the ESR measurement of capacitors. With poor connection cable a ESR value of 0.02ohm can grow to 0.61ohm. You should not expect very good accuracy of measurement results, especially the ESR measurement and the results of inductance measurement are not very exact.


Brand Name

Yaman Electronics

Model Number


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