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Old 16th May 2010, 12:07 am   #1
DAVEHALL
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Join Date: Jan 2010
Location: Coventry, Warwickshire, UK.
Posts: 339
Default Testing transistors - analogue version

Sticky mentions testing transistors with a digital meter which measures junction drop .
However ,in early days ,the test was to measure the junction resistance .
But ,the meter of choice was usually the AVO .
Range 1 - ohms X 100 -
Range 2 - ohms
Range 3 - ohms /100

Now what is correct range ,to avoid damage to transistor .
R1 - battery =9v ,a bit too high for the junction .
R2 - BATTERY =1.5, half FSD = 500 . Current = 3 mA ,fsd =6 mA ,ACCEPTABLE FOR TRANSISTORS .
R3 -BATTERY =1.5V, half FSD = 5, current = BUT TOO HIGH FOR JUNCTION .

Then , base -emitter ( and collector) - one way ,high, other way low resistance .
Emitter/ collector - O/C both ways .

And don't forget that the AF FAMILY had a nasty habit of going collector /screen s/c ( proved by cutting screen) .
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