At my wits end. I've been challenged with setting up a Test Rack for education, and testing in our electrical shop. I've been attempting to setup a PLC5 1785-L40E processor, with a 1771-A4B Chassis; via serial connection to a Laptop. Seems simple enough? My result is, solid red Proc light. (I assume due to no memory, or EEPROM card installed, however it could be a major hardware fault) No COMM light at all, ever. Auto-Config in RsLinx fails. I've made my own cable according to AB's 1784-CP10 pinout. (null modem) I've tried my laptops serial port(COM1), and a USB to Serial adapter(set to COM4). I've lowered the baud on both ports through Device Manager to 2400. (Default for the processor) Confirmed the stop bit, parity, and Error correcting all match the default parameters. I have the chassis dip switches on the chassis set to all off except for 6 (EEPROM memory does not transfer to processor memory.) I have the processor dip switches set 1 2 3 4 5 6 7 so station number is 1. (I found a publication that states some processors don't recognize 0 as a viable address) U D D D D D D And finally yes I've confirmed that the RS-232C dip switches are set for default configuration. DDDUUDDUDU Also note I have 2 identical chassis', and processors, that I've been experimenting with, as well as a second PC with RSLinx installed. The only difference to note is that one of the processors the Ethernet Stat light periodically blinks red. Because I have two sets of hardware to play with, I find it hard to believe however possible; that both sets of equipment have failed with major hardware faults. This leads me to believe that I am fundamentally missing something here. A step I have missed, or I simply have my head shoved up somewhere... ...any ideas?