Installing Internal Accessories; Tcx0-2 High-Stability Master Oscillator - Yaesu FT-990 Operating Manual

Installing Internal Accessories
This chapter de5crib¢S installation of the inter-
nal options available for lhe FT-990.
TCX0-2High-Sta.bility Master Oscillator
The ±O.S-ppm TXC0-2 option can be installed
as
a replacement for the standard ±10-ppm crystal
oscillator. However, doing
so
requires removing
exiSting oomponents from a
double-~ided
. c ircuit
board, which is difficult unless you have the
proper
tools and experience.
We
therefore· recom-
mend that this job be
done by
your Yaes.u dealer, as
damage that might result from improper installa-
tion may not be covered by your warranty (if in
doubt,
check
with your
dealer
b. e forestarting).
0 Remove the power cord fTom the rear panel.
0 Remove the ten screws affixing the top
cover,
as
sho~·n
at L he upper right. Then lift off
the top
oover,and
tl1e·small
plack plas.ti.clabel cover
ror
the- top ·access panel controls. ·
0 Locate the PLL Unit, which
i,s the second plug-
in card from the right side
Of
the chassil; . ( see.
pnoto
at
right), and
careflllly pull
off U1e TM.P
coaxial plug near the front· of the bomd.
0 Remove the two screws
In
the bracket· e arsat the
front and rear edge$ of the board, and Uft tl1e
board
~lightly
out of the chass.is so that you can
remove the .second TMP coaxial plug near the
rear. Remove the board from the chassis.
0
Referring to the photos at the lower right, . c are-
fully unsolder
<1tysrnl
X4001, capacitors
C4047
and
C4048
1
and trimmer
TC4001.
0 Position Lhe
newTCX0-2
board so
th~t
the trim-
mer
hole
is ne!lrext
the
bottom edge
of the board
(see be low). Then push the moduJe leads
through the board and solder in p lilce on the
other
side. The label s hou ld be upside-down.
0
Replace the board in the chassis, using care ro
align the board edges with the tratks at the
front
and back
o{
the slot.
R~conncct
the rear TMP
plug before
replaci11g the
screws. in the brackets.
0
Replace
~he
top cover and screws removed
above
(unless also installing-crysta l fillers now).
T CX0 -2
Orientatio n
Top Cover Removal
-
..
"
PLL Unit
Location
Qscillatac Parts Removal
tMP
RUJO
TMP
<'L\)0
•
..
~
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