To replace the power transistors ( MN2488 and MP1620 )
• you need to have a technique in soldering.
( much faster is cut the transistors pins , but be careful only for
professional serviceman )
click on the link below:Soldering Guide
After taking out the burnt transistors:
• get a multimeter and measure the DC voltages present on
each amplifier output stage ( center of the two resistors in series ).
• • it should be no more than 0.7 V, if it s, remove those pair of power
transistors and test again for output voltages.
the negative probe
of the multimeter to the chassis of the unit.
• Do not connect new power transistors yet.
you may need to power it without it.
Until you sure that the unit powers up and have some/other channel
working to prevent further transistors and components failure.
But if there are still more than 0.7 v on some of the outputs
• Check for VAS circuits and Differential Input Stages
Let me know how you make out with the inspection.
It is a good chance you will find something.
hope this helps, thanks for using Fixya!