ROUTINE MAINTENANCE........................................................................................................... 4-2
REMOVING AND REPLACING PARTS AND ASSEMBLIES .............................................................. 4-3
FIELD AUDIT OF PERFORMANCE................................................................................................ 4-8
Table 4-1: Decoder Chart for Power Supervisor............................................................................4-11
Table 4-2: Layout Diagram of J7, with expected voltages on each pin.........................................4-11
Table 4-3: Typical Power Supply Voltages and AC Ripple ..........................................................4-11
PROBLEMS AND POTENTIAL SOLUTIONS.................................................................................... 5-2
Headphones Don’t Work...................................................................................................... 5-2
RFI, Hum, Clicks, or Buzzes ................................................................................................ 5-2
Unexpectedly Quiet On-Air Levels....................................................................................... 5-2
Poor Peak Modulation Control............................................................................................ 5-2
Audible Distortion On-Air.................................................................................................... 5-3
Audible Noise on Air ............................................................................................................5-3
Whistle on Air, Perhaps Only in Stereo Reception .............................................................. 5-4
Interference From Stereo Into SCA...................................................................................... 5-5
Shrill, Harsh Sound.............................................................................................................. 5-6
Dull Sound............................................................................................................................ 5-6
System Will Not Pass Line-Up Tones at 100% Modulation................................................. 5-6
System Will Not Pass Emergency Alert System (“EAS” USA Standard) Tones at the Legally
Required Modulation Level.................................................................................................. 5-6
System Receiving 8400’s Digital Output Will Not Lock....................................................... 5-7
19 kHz Frequency Out-of-Tolerance.................................................................................... 5-7
L–R (Stereo Difference Channel) Will Not Null With Monophonic Input............................ 5-7
General Dissatisfaction with Subjective Sound Quality....................................................... 5-7
Security Passcode Lost (When Unit is Locked Out)............................................................. 5-7
Connection Issues between the 8400 and a PC, Modem, or Network.................................. 5-8
Troubleshooting Connections .............................................................................................. 5-9
OS-Specific Troubleshooting Advice.................................................................................... 5-9
TROUBLESHOOTING IC OPAMPS.............................................................................................. 5-14
TECHNICAL SUPPORT .............................................................................................................. 5-15
FACTORY SERVICE .................................................................................................................. 5-15
SHIPPING INSTRUCTIONS ......................................................................................................... 5-15
SPECIFICATIONS ........................................................................................................................ 6-2
Performance......................................................................................................................... 6-2
Installation ........................................................................................................................... 6-2
CIRCUIT DESCRIPTION............................................................................................................... 6-6
Overview .............................................................................................................................. 6-6
Control Circuits ................................................................................................................... 6-7
User Control Interface and LCD Display Circuits .............................................................. 6-7
Input Circuits ....................................................................................................................... 6-8
Output Circuits................................................................................................................... 6-10
DSP Circuit........................................................................................................................ 6-12
Power Supply ..................................................................................................................... 6-12
ABBREVIATIONS...................................................................................................................... 6-13
PARTS LIST.............................................................................................................................. 6-14
Obtaining Spare Parts........................................................................................................ 6-15
Power Supply ..................................................................................................................... 6-15
Input/Output Circuit Board................................................................................................ 6-16
Front Panel Subassembly................................................................................................... 6-18
Display Circuit Board........................................................................................................ 6-18
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