5-14
Figure 5
-
6 Troubleshooting Radio RCV Alarms (Sheet 2 of 5)
A
STATUS
Receiver Fault
Receiver On Line
Channel Fail
Radio Dade
Eye Closure
Low RSL
Path Distortion
Radio Frame Loss
RECEIVER
MDR-1084
11/29/04
A
Channel Fail
alarm occurs when RCVR(s) have lost lock and are not
locked on the signal from the farend XMTR(s). Loss of signal also means
loss of CMD path. The most effective method of troubleshooting this type
alarm is to have a technician at both ends of the hop. Farend status
viewing and controls must be performed at the farend site. This alarm can
be caused by a failure at the farend XMTR, RF path/antenna/waveguide
problems, or a failure in the local RCVR or I/O Interface.
Start by isolating the fault to one end of the hop or the RF
path/antenna/waveguide. If the farend XMTR is protected, switch XMTRs
and see if alarms at the RCVR end clear. If so, the problem is at the XMT
end and the path and RCV end are ok. If the RCVR alarms do not clear
(and/or the XMTR is not protected) proceed as follows:
1.
Observe
RX (RSL 1) dbm
on the analog monitor screen and compare the RSL level with the
TYPICAL
RCVR THRESHOLD (DBM) BER = 10-6
, for the type and capacity of radio, listed on Tabe 1-3, Physical,
Environmental, and Electrical Characteristics, in the General section of this instruction book. If the RSL is
too low (below the RCVR threshold), the RCVR will not lock to the farend XMTR. The problem is in the
farend XMTR, is an RF path problem, or is a farend or local antenna/waveguide problem.
2.
Troubleshoot farend XMTR.
If the RSL is above the listed threshold, troubleshoot the local RCVR. Start by isolating the fault to the RCVR
module or I/O Interface module.
a.
Observe
RX (AFC MON)
voltage on the analog monitor screen. This is the correction voltage for the
crystal oscillator. The voltage should be -3.0 ±0.5 Vdc, indicating that the crystal oscillator is on center
frequency. If not, remove and replace crystal oscillator subboard on RCVR. If the
RX (AFC MON)
voltage is correct, the failure could still be the RCVR or the RCVR circuits in the I/O Interface module.
The most probable cause is the RCVR.
b. Remove and replace RCVR. The crystal oscillator subboard and capacity key must be removed from
the suspected RCVR and installed on the spare RCVR. If the alarm is stil not cleared, remove and
replace the I/O Interface module.
Summary of Contents for MDR-8000
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