Tektronix T912 - Page 63

Service
Information—
T91
2
Power
Supply Board
Replacement
To
remove the
Low Voltage
Power
Supply
from the
Instrument:
1.
Remove
the
two
retaining
screws
holding
the
heat
sink
to
the
rear
subpanel.
2
Remove
the bolts near
C738 and
Q774 (the
ones
holding
the Power
Supply board
to the crt
shield).
The
other
two
bolts
hold the
transformer
to the
Power
Supply
board.
3.
Unplug P784
and
P720.
Disconnect
P7
from
J7on
the
Interface
board by lifting
the
Power
Supply
board
and
transformer
out.
(See Fig.
5-8.)
To reinstall
the
Power
Supply
board, reverse
the
above
procedure.
Interface
Board
Replacement
To remove
the
Interface
board
from the
instrument:
1.
Remove
the
Vertical
Amplifier
and
Time
Base.
2.
Use a small
screwdriver
to
remove the
clip
holding
Q458
to the
rear subpanel.
3.
Remove
the
front-panel
FOCUS
and INTENSITY
knobs and
shafts.
4.
Remove
the
high-voltage
shield
(two
screws) and
the
two
posts
underneath
the
shield.
5.
Disconnect
the
following
plugs
from the
Interface
board:
a.
CAL
OUT (P24,
unmarked
on some
boards),
a
brown on
white
wire.
b. P419
from
J419 (a
red
on white
wire from Z
AXIS
connector).
Push
wire
through
hole in board.
c.
P470
from
J470, a two
pin plug
(mis-marked
P9on
some
boards);
with
a red wire
and a brown
wire
from
the
hole
in the
crt
shield.
d.
P9
from J9, a ten
pin plug
(mis-marked P470
on
some
boards). Wires
to
this
plug come
from
storage
board.
e. P982
from J982 (a yellow
on
white
single wire from
crt neck
pin).
f. P70
from
J70 (two brown
wires
inside tubing),
some boards
are mis-marked
J7
for
this connector.
g.
Carefully lift
cable
retainer clip with
a small
screwdriver
and
slide
cable out
of
clip; then unplug
P465
from
J465 (a
4
pin plug): P466
(unmarked
plug,
yellow
on white
single wire);
and
P475 from J475
(a 4
pin
plug with
unmarked
index
at
end next to J982).
h. PI
38
from
J
138 (a blue
on white
wire
to
unmarked
pin
near LR138);
PI 48 from
J148
(a brown
on white
wire
to unmarked
pin
near
LR148);
pull wires
down through
board.
6.
Disconnect
J7
from
P7 on
Power
Supply
board by
lifting
the Interface
board
toward
the
top and
back
of
the
instrument
so that
the
POWER
(ON)
light
pipe
disengages
from
DS796
housing,
and the
BEAM
FINDER
and
OFF ON
(POWER)
buttons
slide
back
out
of the
front
panel
as
J7
and P7
separate.
7.
Reverse
the above
procedure
to
reinstall
the
Inter-
face board.
Be careful
not
to let
the
edges
of the high
voltage
shield
touch
adjacent component
leads
on board
after
reinstallation.
Storage
Board
Replacement
To remove
the Storage
board:
1. Remove
INTENSITY,
FOCUS,
and
ENHANCE
knob-
and-shaft
assemblies
out through the
front
panel.
2.
Unplug P9
from J9
on the Interface
board
(a ten pin
plug,
mis-marked P470
on
some
boards).
3.
Unplug P950 (an
eight
pin
plug)
from
J950.
4. Insert a
small
screwdriver
between
the switch
shaft
tip and
extension
shaft,
and
carefully
disengage
extension
shafts from
the BEAM
FINDER,
OFF ON
(POWER),
INTEG,
and ERASE
switches.
Slide the
shafts
forward
until
disengaged,
then
slide
them
back
through
the front
panel to remove.
5-16
REV. A APR 1977