AC Control Board repair

Discussion in 'Technical Repair' started by Marco Mandelli, Jun 7, 2018.

  1. Marco Mandelli

    Thread Starter New Member

    Jun 7, 2018
    Hi, i'm trying to fix an AC control board that is no longer produced by Mitsubishi
    I have already bought and substituted broken components (a resistance, a capacitor, a transistor and a diode). When i try to connect the board again it instantly blows the 250V 1A fuse. I don't know if there is something short-circuited or maybe i missed something with transistor (it's not the same as the previous cause it's not longer in production, it was an 2SC4960 now is a KSC5027OTU ) because the new transistor has an Ic of 3A while the previous has an Ic of 1A as i see from the datasheet. Or maybe the problem is now in the transformer but i cannot find the model. I'll link some photos of the circuit section
    Thanks for help
    IMG_20180607_210624.jpg IMG_20180607_210557.jpg
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    Looks like a switchmode psu, with a 8 pin chip supplying the pulses to the transistor. The chip Ic856 is the main circuit, can you see what number is on it. If it keeps blowing the fuse then the transformer or the transistor is going into over current mode, probably due to a short on the output of the psu, check the diodes from the transformer and any shorts across the output capacitors.