Tektronix 7a11 Instruction Manual page 37

Front Panel
R
emoval .
R
emove all front
p
anel kn obs,
u sing an alien wrench on
t
he POSITIO N , VOLTS/DI V,
VAR IA BLE an d Offset COARS E
a
nd F I NE kno bs. (T he
VOLTS/DIV
a
nd Offset COARS E kno bs each have two
screws .)
T
he ID EN TI FY and STEP ΑΤΤΕΝ
B
A L k no bs are
press-on type.
R
emove the nut and washer from th e O FF-
SET O UT connector, using α Spi ntite®wrench. Spr ing the
front panel free from th e front casting by using α wi de, th in
b la de at t h e top and
t
he
b
ottom .
Front Casting R emoval . The front
p
anel must be re-
moved first. Then remove t h e screws
f
rom the four corners.
I nd ivid ual components must
b
e unsoldered or disconnected
for complete removal of the front casting.
Fr ont
P anel Cont rols. POSITIO N -
R
emove the set
screw
f
r om kno b
a
nd remove the hex nut from the front.
Offset COAR SE, FI NE -
R
emove three set screws from the
kn o b s and remove the hex nut from
t
he front. ST EP
ΑΤΤΕΝ
B
AL - Pull the knob off the front, remove set
screw
f
rom the mounting sleeve
b e h i nd the front casting,
an d remove the front pa n el . Th e n remove screws from the
front casting, and move th e casting to the front enough to
remove the potentiometer.
VOLTS/DIV -
T
he wafers on
t
he cam a r e number-coded
on
t
he schematic diagrams . The numb e r indicates
t
he cam
p
osition in
t
he switch assembly, co un ti ng from the front
(mounti ng end) . Access to the cam switch can be obtained
b
y removi ng the Ca ble Connector Cover at the front of the
right side of the Plug-In Un it . The switch cover can
b
e re-
moved after removi ng two screws
f
rom its top.
To
t
horoughly inspect the switch contacts, the cam
assembly of t h e switch must
b
e removed .
R
emove the
VAR IA BLE kn ob an d
s
haft after loosening the alie n screw
at the
b ac k of t h e cam switch housing .
R
emove the nut
fr om t he back of the front panel VO LTS/DI V switch
bushing. Pull
t
he cove r from th e left si d e of the W1 and
remove th e fo ur screws wh ic h hold the cam assembly in
place. -Lift the cam assembly away
f
rom the ci rcuit board
and move it toward the back of the 7 A 1 1 to fully remove
it .
U
se caution so that the boar d-mou nted contacts are not
d amaged. It is recommen ded that the cam assemb ly cover
b
e left in place when the assembly is removed
f
rom the
b
oard . The cover will hol d
t
he assembly together.
R
eplacement of the cam switch contacts requ ires special
tools an d caref ul attention to alignment and spacing. It is
recommended that repairs be
d
one
b
y α Te ktronix
R
epair
Center . In repairing
d efective switches, α repair kit and α
s
kille d techn ician are n ecessa ry ingredients. The repai r kit
(whic h includes tools, instructio ns, replacement contacts,
and lu brica nt) can be obtained from Te ktronix Field
Offices under Part No . 040-0541-00.
(1)
R
emove the cable connector cover.
Maintenance-7A11
VARIABLE - Potentiometer can
b
e removed
b
y re-
moving t h e Ca ble Co nn ector Cover, unscrewing
t
he nut
from the front of the potentiometer housi ng, unscrewing
t
h e .050 inch alien set screw at the front of the potentio-
meter shaft, and sliding the pote ntiometer out the
b
ac k. To
remove the VAR IA BLE switch co ntrol assemb ly, first re-
move the potentiometer, then loosen the set screw at the
front of the switch assembly, pull
t
he VARIA BLE
s
haft
forward and lift the control assembly out. The housing for
the switch contact and slide is not removable, si n ce it is
heat-welded in place. To inspect the switch contacts, re-
move the VOL TS/DI V cam assembly and move the slide
forward out of its housi ng; the VAR IA BLE potentiometer
d oes not have to be remove d .
Pushbutton Switches :
E
xcept for pin connector and
lamp r eplacement, these switches are not
r
epairable. To re-
place α lamp, remove the screw and metal cove r
f
rom the
rear of t he switc h housing . Un solder and re place the lamp,
installing the new one in an identical
p
osition. See the Pin
Connector to pic fo r pi n co nnector re pairs.
Pushb utto n switches can be
r
emoved as follows: R
emove
the plug-on co nn ector from the rear of the switch; r emove
the instrument front- panel according to inst ructions appea r-
ing elsewhere in this sectio n ; remove the one screw (from
the front casting) whic h hol ds the switch in
p
lace .
Ci rcuit Board . Component locations and wire color
coding are shown in Fig . 4-8 through 4-12 . Transistor termi-
nals are identified in Fig . 4-9. Circuit board access is ex-
plained in
t
he followi ng topic .
Circuit Board Access . Access to the transistor-side can
be obtained by pulling
t
he left side cover off. For limited
access to the reverse side,
p rocee d as follows:
(2) Open
t
he Probe Accessories case, remove th e two
nuts which hol d it in place, and lift it ou t.
(3)
R
emove the nut and ca ble clamp in the
b
ack near
the bottom .
(4) L ift the rear of the outer
s
hield, freeing it from
t
he stu d s. Then remove it, ma nipulating it as necessary .
Total access to the
b
ac k of the
b
oard can
b e obtaine d as
follows:
(1)
R
emove the outer s hield as
j
ust described .
4-11