ccef001@ut-emx.UUCP (Mark Klotzbach) (06/05/89)
For those of you out there who build your own Ethernet Transceiver
cables, I have drawn up a simple cable tester that can be used to catch
a large number of your non-shorting cable problems. We use the cable
tester to check if the power pins (6 & 13) are in proper postion. In the
past we have had many a computer interface board or power supply blow because
of the mis-positioning of these pins resulting in a power short or inversion.
The tester is very simple (a continuity tester) and is inexpensive. It is
also a lot easier to use than an Ohm meter and can be used by one person.
Here goes:
----- PARTS LIST -----
4 - 9 Volt Batteries
4 - 9 Volt battery clips with wires
4 - LEDS (any color will do)
4 - 85 ohm resistors (I like my LEDS bright and batteries are cheap)
1 - DB 15 Male connector
1 - DB 15 Female connector
1 - 4 pole single throw switch
Electric tape
1 - DB 15 802.3 connector locking kit
----- Design -----
2 2
-------------/\/\--------------->>----------|
| 85 ohms |
| + |
----- /__\ /
--- 9 Volts LED ( \/ ) /\/
----- \--/ /
--- |
| - |
| / 9 9 |
--------------o o--------------->>----------
This circuit is to be repeated for pins (3,10),(5,12), and (6,13). I put
the female DB 15 connector on the battery side (equipment side) so that I
never accidently plugged in the computer with the battery plugged into the
other end of the cable. Since the signals are DC I would assume that there
would be no damage to the transformer coupling, but why take chances. I would
rather lose a transceiver than an interface board. The reason for the switch
is so that the led connector can be plugged into the battery for storage. The
switch disables the power during storage. I hope this helps you as much as
it has helped me. Ohming out cables can get old real quick.
Mark Klotzbach
University of Texas
Network Systems Office