Sorry that I didn't understand it with the first post.
I think it has to do with the Carriage Return (CR, '\r', 0x0D) and/or Line Feed (LF, '\n', 0x0A).
If you connect the weigher to the PC, you probably send the code with CR and/or LF.
You could read the specification of the weigher, but I would start to send them both.
Mx3232Serial.write(0x01);
Mx3232Serial.write(0x73);
Mx3232Serial.write("\r\n");
or this
Mx3232Serial.write(0x01);
Mx3232Serial.write(0x73);
Mx3232Serial.println(""); // send CR LF
or even this
Mx3232Serial.println("\x01\x73"); // send 0x01, 0x73 with CR LF