Question:

Do the transistors MN2488 and MP1620 need to be matched pairs?

by Guest565  |  12 years, 7 month(s) ago

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Hello,
I try to repair a Sony SA-WX90 which, among some other faulty components, has two pairs of shorted MN2488/MP1620 transistors. I have purchased 15 of each type and measured their hfe. For the MN2488, it ranges from 5000 through 10000, whilst the MP1620´s range from 16000 through 35000. Is this big difference in some way foreseen in the circuit design or do the transistors absolutely need to have the same hfe?
Best regards!
Staffan Casserstål
Sweden

 Tags: matched, MN2488, MP1620, Pairs, Transistors

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  1. Guest1354

    They need to be matched pairs.


    Before connecting the output transistors, insure that the drive to


    ( +1V and -1V respectively ) the base of the Darlington Transistor  is OK


     


    and check for idling current, these should not be more than 80mA


    higher  value will just blow away your new transistors, even without


    connecting the loads ( speaker ) in a few minutes.

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