Orban OPTIMOD-FM 8600Si, Operating Manual

Page: 287 / 356

OPTIMOD-FM DIGITAL TROUBLESHOOTING
5-1
Section 5
Troubleshooting
Problems and Potential Solutions
Always verify that the problem is not the source material being fed to the 8600Si, or
in other parts of the system.
RFI, Hum, Clicks, or Buzzes
A grounding problem is likely. Review the information on grounding on page 2-11.
The 8600Si has been designed with very substantial RFI suppression on its analog
and digital input and output ports, and on the AC line input. It will usually operate
adjacent to high-powered transmitters without difficulty. In the most unusual cir-
cumstances, it may be necessary to reposition the unit to reduce RF interference,
and/or to reposition its input and output cables to reduce RF pickup on their shields.
Particularly if you are using a long run of coaxial cable between the 8500 and the
exciter, a ground loop may inject noise into the exciter’s composite input—especially
if the exciter’s input is unbalanced. A Jensen JT-123-BMCF transformer can almost
always cure this problem—see page 1-15.
The AES3 inputs and output are transformer-coupled and have very good resistance
to RFI. If you have RFI problems and are using analog connections on either the in-
put or output, using digital connections will almost certainly eliminate the RFI.
Unexpectedly Quiet On-Air Levels
The ITU412 multiplex power controller may have been turned on accidentally. See
step 1 on page 2-23.
The 8600Si may be in stand-alone stereo encoder mode. The active on-air preset de-
termines this.
The 8600Si may not be controlling peak modulation as desired. See the next topic
below.
Poor Peak Modulation Control
First, check whether the final clipper is active (step 6 on page 2-29). If you are using
the analog or digital output to drive the transmitter, make sure that this output is
not receiving the
M
ONITOR
signal (step (10.B) on page 2-31).