APC 7920 PDU #2 DIY cheap serial console cable for password reset
118A step-by-step tutorial on making a specialized serial cable for resetting the password on an APC 7920 PDU. This cable should work on a wide variety of PDUs and UPS units from APC.
The equivalent console cable from APC (model: 940-0144A) is hard to find, and it costs 20-40Euros even used from Ebay when you include shipping, so it is easier/cheaper to make it yourself.
Total cost for building components is around 2 Euros.
PINOUT:
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RJ12 (APC) DB9 (female serial)
Pin 2 -----------to----------- Pin 5 (GND)
Pin 3 -----------to----------- Pin 2 (RX)
Pin 4 -----------to----------- Pin 3 (TX)
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One end of the APC serial console cable uses the RJ12 plug with 6 pins, while the other goes to a standard 9-pin DB9 female connector.
Here the most simple null-modem cable is built without any hardware handshaking (there are only three wires connected).
The other wires are not necessary, they are there only to improve the mechanical stability of the connector.
I have bought the RJ12 plug, the DB9 female connector and the plastic housing for the DB9 connector from Conrad Electronics who sells worldwide, so if you want to order the same things, or want to see what to order from an other store, just click on the links below.
I had the Cat5 cable and the RJ12 crimper tool laying around.
To save money, you can easily get 1-2 meters of Cat5 cable and just borrow an RJ12 crimper tool from your job or from a friend.
The colors I picked from the Cat5 cable for better contrast:
green-white (RJ12, Pin 1) ------not connected
green (RJ12, Pin 2) -----------to----------- Pin 5 of DB9 (GND)
orange (RJ12, Pin 3) -----------to----------- Pin 2 of DB9 (RX)
brown (RJ12, Pin 4) -----------to----------- Pin 3 of DB9 (TX)
orange-white (RJ12, Pin 5) ------not connected
brown-white (RJ12, Pin 6) ------not connected
blue ------cut it off
blue-white ------cut it off
RJ12 plug:
http://www.conrad.com/ce/en/product/1303477/econ-connect-MPL66R-Pin-RJ12-Plug-straight-Clear?ref=searchDetail
DB9 plug:
http://www.conrad.com/ce/en/product/1303906/D-SUB-pin-strip-180-Number-of-pins-9-Solder-bucket-econ-connect-1-pcs?ref=searchDetail
DB9 plastic casing (optional):
http://www.conrad.com/ce/en/product/1311408/D-SUB-housing-Number-of-pins-9-Plastic-180-Black-econ-connect-1-pcs?ref=searchDetail