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Old 16th May 2010, 7:21 pm   #3
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 5,496
Default Re: Testing transistors - analogue version

Herald1360's method is exactly how I test transistors. (The wet finger directly between collector and emitter leads, with approximately the same area of contact and finger pressure as you used between collector and base, allows you to 'calibrate out' your current saliva conductivity).

You can also use this method to test power mosfets - the wet finger between drain and gate turns them 'on' and the meter deflection should remain when your finger is removed; finger between source and gate should turn them 'off' and now the meter should stay at infinity when your finger is removed. Drift of meter needle indicates leakage and possible electrostatic damage (assuming the transistor is clean!). Always have your finger roll onto the gate lead last, and break contact with gate lead first.
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