Thread: Toshiba IC70
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Old 18th Oct 2011, 5:16 pm   #64
julie_m
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Join Date: May 2008
Location: Derby, UK.
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Default Re: Toshiba IC70

If you've swapped over the collector and emitter, the transistor shouldn't have been damaged permanently; but it will have much lower hFE in this configuration. (A boiler ignition board I worked on once worked perfectly happily with a BC547 reversed. We had been shipping them with the transistor in wrong-way-round for about 3 months before anyone noticed it didn't match the silkscreen ).

Be suspicious of anything in a TO92 package! The middle lead is usually the collector, except when it's the base (as in BC547, 557, 337 and 327). If in doubt, test it -- even cheap multimeters have a transistor test function nowadays. Identify the base by the usual process of testing as diodes, then insert the transistor in the test socket both ways around. Whichever way gives the higher gain reading is correct.

I'd be tempted to fit a BC327 and 337 (both C-B-E) and a different bias resistor; try 100R for starters and adjust for minimum current with no signal, then apply a signal and adjust again for best compromise between distortion and current.
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