Component tester MK-168



This is a fairly universal component tester, it can recognize a lot of different component types and give some parameters for them.
It is also fairly cheap on ebay



How does it look



This tester is in a box with 2 mm connections, it includes test wires.



It does also include a circuit board with a socket and a smd pattern. The box has a connector for external power, but can also fit a 9 volt battery inside.






Inside it is made very nice with connectors and a circuit board designed for this box.



The display is a standard display with 2 lines with 16 characters.



All the electronic is placed under the display.
The circuit is very simple, the microprocessor do everything. It has 3 pins connected to each of the 3 terminal, one directly for ADC, the two other pins with different resistors between.



The adapter has a smd pad, but with fairly limited functionality.







Resistors



The ohm range looks fairly good.



The display it not graphical, but because it is possible to program some characters it can show a useable symbol.



Capacitors



It cannot measure small capacitors.





Inductors



With inductors it uses the resistor symbol, but shows a inductance in addition to the resistance. It cannot measure small inductors.





Diodes



Due to the 5 volt test voltage it cannot see zener diodes above 5 volt.



There is a bug in the symboles, one of the diodes are not programmed correctly.



SCR (Thyristors) + Triacs



It cannot detect most SCR and triacs, because the tests currents are too small. Only very small types are detected.



Triac is spelled out and MT1 and MT2 is shows as 1 and 2.



BJT (Bipolar junction transistors)



It do see the diode in the transistor, but not the resistor.



There is not space for a transistor symbol on the display, the letters NPN or PNP are used instead.



The faulty diode symbol is a bit confusing to see here.



FET (Field effect transistors)



It can detect normal fet transistors, but not a deflection transistor.





IGBT (Insulated gate bipolar transistor)

Not supported



Voltage regulators

Not supported



Technical details

Components are tested with 5 volt signals.
When on the current consumption is 10mA to 27mA.
When off the current consumption is 0.



Conclusion

The tester will recognize many different components and show the values. For passive parts the precision is fairly good.
It can recognize the common semiconductors, but fails on some more special types. There is also the "problem" that any testing values shown for diodes, BJT and FETS are at unspecified conditions and the values will change with conditions.
I could have wished for a better SMD pattern.

For the money it is a good tester for leaded parts and acceptable for smd parts, but the defect diode symbol is confusing.



Notes

This tester is based on this design:
Original design article in German
Improved design (czech clone)
Software

About the testing of testers