Fault Not Found - HP 27115A Installation Manual

Fault Not Found
If
a
link
hardware problem persists, check for a marginal fiber-optic transmitter,
receiver, or duplex cable using optical meter equipment. This takes two steps,
the fIrst of which is a direct measurement of the transmitter's output. The
second measures the receiver's input and indirectly tests the receiver itself.
Before proceeding, test the transmission of the 3O-cm loopback cable. It should
show no more than 2 dB loss.
1. Measure the output of the peA's transmitter:
a. First, using the 3O-cm loopback cable, measure the transmitter's
output. The received signal must be greater than -21 dBm (that is,
closer to 0).
b. Then, attach the duplex cable between the transmitter and meter.
The received signal must now be greater than -27 dBm. If it is, both
the duplex cable fiber and the transmitter are good. If not, either
maybe bad.
2. Depending on the outcome above, take one of the following actions:
a. If both of the above readings failed, the peA's transmitter is faulty.
Replace the peA.
b. If the duplex cable reading failed, but the loopback cable reading
passed, follow to the "Cable Fault Isolation" procedures provided
earlier in this chapter.
c. If both readings passed, check the strength of the signal from the
external device using the same technique described above. If this
reading is greater than -27 dBm (indicating the transmitter on the
disk drive is good), replace the peA, because its receiver is bad.
If both the fIrst readings were within tolerances, and this test
showed that the disk drive's transmitter is good, then the disk
drive's receiver is bad.
For difficult faults, other recommended actions include:
1. Replace the peA PROMs.
2. Recheck the system hardware and software configurations.
3-14 Troubleshooting and Diagnostics