Multi-Function Tester TC-1

I picked up one of these little testers off eBay for AUD$25 recently, and it arrived yesterday - my first impression is that it's pretty good for the price.

Previously I have been using the RG Keen method for testing germanium transistors, using a little test circuit from Guitar FX Layouts and a multimeter.  

There's also a handy online calculator that can be found here to provide results.  It works pretty well, and it's certainly the cheapest option available.  

This is great for germanium transistors, but what about everything else?  I bought a job lot of old transistors a while ago (germanium and vintage silicon), and quite a few of the vintage silicon are unidentifiable.  

What I was lacking was a way to quickly identify what the random transistors are in terms of type, pinout and hFE.  My multi-meter has a hFE test, but you have to know the pinout and type of transistor being tested - it's next to useless....    This cheap little tester fills that gap.

What can it test / identify?

• BJT Transistors

• MOSFET / JFET

• Diodes

• Resistors

• Capacitors

• Inductors

• + Thyristors, Triacs and low-voltage batteries

Easy to use

• Attach the component in and turn it on - wait a few seconds, and the result will appear.

• It identifies the part; there's no need to give it a range to tell it what to measure.

• The small colour screen is easy to read, just large enough to do the job.

But.....

So I grabbed a few transistors to test, and found the leakage results to be a little different between test methods.

The results below are for a Valvo OC75, taken directly from one test to the other, with minimal time and handling between tests (all handling was done with small pliers).  It was 30 degrees Celsius / 86 Fahrenheit, a pretty standard summer temperature where I'm located.

Note that the hFE is close enough the leakage is off by 76mA (0.526mA vs 0.450mA) - which is not a huge amount, but enough to annoy me over the inconsistency.  

As it turns out, this is relatively common, as different test methods apply different amounts of current to conduct the test, resulting in different outcomes.

RG Keen method

First reading = 1.3v
Second reading =  2v
1.3 / 2.472 = 0.526mA leakage
(2 - 1.3) * 100 = hFE 70

Multi-function tester

hFE = 73
Ube = 109mV
Ic = 1.2mA
Iceo = 0.45mA (this is leakage)
Ices = 31uA