[Boatanchors] [CARSHamRadio] Re: transistor help needed

[Ron]

>> Thanks to all that responded to my transistor
>> question.However, I still do not know which 
>> lead is which!

Here's how to identify transistor leads, using a VOM. 

Select diode test or an Ohms range for conveniently 
reading a few hundred to a few KOhms. Measure 
resistance between every pin pair, then reverse the 
VOM probes and repeat (total of 6 measurements). 

Two pin pairs should yield a low reading in one direction 
and a high or open reading the in the other. The third pin 
pair should yield a high or open reading in both directions. 
If this is not the case, the transistor is bad. 

Note the lowest reading.

The two pins that resulted in a high or open reading, 
both ways, are the emitter and collector. Therefore, 
the remaining pin must be the base. 

Now short the base to one of the other pins. Measure 
between this shorted pair and the third pin, in both 
directions (two measurements).

If one reading is high or open and the other is lower 
than the measurement noted above, the pin shorted to 
the base is the collector. You're done. 

If, however, both readings are very high or open, short 
the base to the other pin instead and repeat the two 
measurements. If this identifies the collector as above, 
you're done. If both readings are high or open, the 
transistor is bad. 

BTW, if you know the polarity of the VOM (in most -- but 
not all -- the red probe is positive), the transistor polarity 
(NPN or PNP) can be determined. 

-- Ron