Bipolar Junction Transistor Testing Basics

Discussion in 'DIY' started by EchoWars, Jul 15, 2005.

  1. C_D

    C_D New Member

    Messages:
    32

    I too have been working professionally on electronics for many years (40+ but who's counting) and concur: pulling working parts for specious testing is poor practice. Almost nobody has a car tire removed from the rim to "inspect the inside for abnormal wear". Heating, removing and handling functioning components, without solid foundation, is just adding more reasons for premature failure. Measure voltages first and compare with manufacture's data. When schematic is not available, draw out suspect stage and do the math. Voltage drop is absolute best starting point to asses current conditions (pun intended). Only times I ever used curve tracing were when I was pushing components in my custom designs. Getting out to the SOA limits occasionally gave merit to using curve tracer and matching everything. For repairs in general, especially systems designed over 30 years ago, basic troubleshooting starts with DC voltage measurements and common sense applications of circuit theory. Before looking into any curve tracing options, it is much more beneficial to invest in a good quality 5 amp VARIAC. DBT will not help one trying to reform 'ltyic capacitors.
     
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  2. TECH---NICS

    TECH---NICS Member

    Messages:
    53
    Location:
    euROpa
    hello folks , i need a opinion on my problem.......denon pma 1520 , big baby , power transistors are 2 x 2sa1492+2 x 2sc3856 per channel.........one channel broken ........unfortunatelly i am in an isolated area now-heavy snowfall- and i do not have a multimeter to test those 4 transistors so i did this.........desoldered all 4 trans. and i got relay coupling on , other channel working ok , so those 4 trans are my problem.......since no multimeter, i resoldered one by one , after each one i powered amp and wait relay click on.......in one case , after resoldering a 2sa 1492 relay didnt click on .......now 3 are soldered on motherboard 2 x2sc3856 and 1x2sa1492...........it is correct to think that 2sa1492 - in which case relay didnt click- is my broken one? it is possible 1 of 4 to break down?
     

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