Just repaired one of those. At mine
The TL431 was shorted. The 300 Ohm resistor above it was open.
Two 10 Ohm base resistors for the two TIP 147 were about 1k5 and 10k.
The BD139-16 which drives the two TIP147 via the 10 Ohm resistors was CE shortet, which leaded to the vaporization of their 10 Ohms base resistors.
The BD140-16, which switches the 48V supply if you press the output button, was CE shorted.
These transistors are 80V rated, so there must have been a nice overvoltage or inverse voltage at the output, i don't know, i got it broken.
As it uses internal 48V and -8V for the regulators it is much easier to get under the -8V where the ouputs can't be switched of any more. I think it is sufficient to connect the 2 outputs in series (+ to -) instead of parallel (+ to +) to kill one of them. The outputs are missing any protection diodes.