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OPTIMOD-FM 2200 TROUBLESHOOTING
5-1
Section 5
Troubleshooting
page contents
5-2 Problems and Possible Causes
5-2 RFI, Hum, Clicks, Or Buzzes
5-2 Poor Peak Modulation Control
5-2 Audible Distortion On-Air
5-3 Audible Noise on Air
5-4 Whistle on Air, Perhaps Only in Stereo Reception
5-4 Shrill, Harsh Sound
5-4 Dull Sound
5-4 System Will Not Pass Line-Up Tones at 100% Modulation
5-5 System Will Not Pass Emergency Broadcast System
("EBS" USA Standard) Tones at the Legally-Required Modulation Level
5-5 Interference from Stereo Into Subcarriers
5-6 19kHz Frequency Out-of-Tolerance
5-6 L-R (Stereo Difference Channel) Will Not Null With Monophonic Input
5-6 General Dissatisfaction With Subjective Sound Quality
5-7 Troubleshooting IC Opamps
5-7 Technical Support
5-8 Factory Service
5-8 Shipping Instructions
CAUTION
The installation and servicing instructions in this manual are for
use by qualified personnel only. To avoid electric shock do not
perform any servicing other than that contained in the Operating
Instructions unless you are qualified to do so. Refer all servicing
to qualified service personnel.
5-2 TROUBLESHOOTING OPTIMOD-FM 2200
page
Problems and Possible Causes
Always verify that the problem is not the source material being fed to the 2200, or in other
parts of the system.
RFI, Hum, Clicks, Or Buzzes
A grounding problem is likely. Review the information on grounding on page 2-12.
The 2200 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 almost always operate adjacent to
high-powered transmitters without difficulty. In the most unusual circumstances, 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 2200 and the exciter, a
ground loop or other problem may inject noise into the exciter's composite input --
particularly if the exciter's input is unbalanced. This problem can almost always be cured
by the Orban CIT25 Composite Isolation Transformer (see page 2-12).
Poor Peak Modulation Control
The 2200 ordinarily controls peak modulation to an accuracy of