Yeasu FT990 Problem

Page 1 2 3 4     BACK TO CONTENTS

My Yaesu FT990AC would intermittently stop working. The S meter light would illuminate but no display and no sound. Also the memory would be lost. Seemed like a power supply fault. Reference to the circuit diagram pointed to a failure of the 5 volt line which is derived on the regulator board. The problem turned out to be dry joints on the 5 volt regulator. The following procedure may assist others having this problem. Ensure the mains supply is not connected.  Remove the bottom cover. Remove the masking tape securing the thin wires under the PSU. Carefully snip and remove a few cable ties. Remove the four screws fixing the PSU to the chassis.