Icom IC R8500 Service Manual Addendum page 219

CR-293
HIGH STABILITY CRYSTAL UNIT
A temperature-compensating crystal with a stability of
± 3 ppm is built-in to the receiver. For more demand-
ing operation, the CR-293
is available. It has a stability of ± 0.5 ppm.
UNIT
q Remove the bottom cover as shown on p. 37.
w Remove 6 screws from the metal plate, then
remove the metal plate and shield cover.
e Remove 10 screws from the PLL unit, then open
the unit to expose the bottom.
r Unsolder the feet of the internal crystal unit, then
remove it.
t Place the CR-293 in the space available as shown
in the diagram, then solder its feet into place (6
points).
y Adjust the reference frequency using a frequency
counter.
u Replace the ground spring to its original position.
i Return the shield cover, metal plate and bottom
cover to their original positions.
NOTE: The CR-293 is an oven-type crystal unit,
and the specified frequency stability described
above is guaranteed 1 min. after power ON.
HIGH STABILITY CRYSTAL
Ground
spring
3 - 2
Metal plate
Shield
cover
PLL unit
CR-293
Internal
crystal
unit
PLL unit