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Help with power transistors !

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New Member
I have constructed the DC-AC inverter by Tony Van Roon.
I don't have the TIP41 or TIP42 transistors so i replaced them with 548 and 558 transistors.
i put the output through a transformer and it works(120VAC).
but when i replace them with the JE2995 and the 3055 the transformer steps down the voltage, i've tried both ways on the transformer.
Maybe it doens't work that way, how can i make this circuit more powerful (300W)?

i measured the voltage without the transformer with the power transistors and the voltage appears OK.
i replaced the transformer but same thing happens.


Active Member
TIP series is power transistor in TO-220 package, not changeable with small signal transistors e.g.558. Use BD241 for NPN,BD242 for PNP position. (or BD139,140) Small signal transistors can't produced enough base current for output transistors...
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