Troubleshooting Guide, Squelch Adjustment

LBI-39175A

ISOLATION

TRANSFORMER

4-OHM LOAD

1 : 1

Not required if instrument input is balanced with respect to ground.

DISTORTION

ANALYZER

AC VOLTMETER

Figure 4 - Audio Isolation Transformer

SQUELCH ADJUSTMENT

Squelch threshold has been set at the factory to 8 dB SINAD. Adjustment of the threshold requires changing the Tracking Data. To change the Squelch Tracking Data, follow the iterative procedure set forth in the "TRACKING DATA" section, except let the desired squelch threshold level replace the 8 +1, -0 dB SINAD level set at the factory. BE SURE TO CHANGE THE TRACKING DATA FOR ALL FREQUENCIES GIVEN IN TABLES 2 AND 3. Otherwise the level will not be consistent across the frequency band.

TROUBLESHOOTING GUIDE

INTRODUCTION

This radio is designed to be serviced by replacement of modules and/or circuit boards. As such, there are very few serviceable component parts contained on any of the circuit boards within the radio. Normally, defective boards should be replaced, and returned to an Authorized Service Center. A list of serviceable parts is given in the next section.

MICROPHONICS

Synthesized radios tend to be sensitive to shock and vibration, creating microphonics. The construction of the ORION radio with its die-cast aluminum frame, cast shield, and multiple board-mounting screws, provides a high degree of immunity. When removing printed circuit boards or shields, note the location of all mounting hardware.

When servicing the radio be sure that no solder build- up has occurred on the chassis or shield.

To assure a high degree of resistance to microphonics be sure to replace exactly, all hardware removed. Be sure that all mounting screws are properly torqued and shields are in place. Refer to the Mechanical Layout Diagram found in LBI-38909.

NOTE

Loose or rubbing parts, especially in the VCO area, are particularly sensitive and can cause microphonics. Again, be certain all hardware is properly installed and torqued.