I suspect you unintentionally shorted one output. While these are
short-protected, they do run hot when this happens.

Check the output volgate on the outputs: pin 3, 6, 8, 11 (this is from heart,
pls verify). If it is either +15 or -15 you're OK, if it is
significantly different you found your root cause.
Pls also check voltages with the chip removed (socketed?).

Typical cause for this is an incorrect serial cable and/or broken serial
connecter (bent pins?), or bad internal connector (flatcable incorrect).
The art to make correct serial cross cables has been largely lost in
30 years and I suspect that's your cause.

73,

Geert Jan PE1HZG