Tektronix T912 - Corrective Maintenance

Service
lnformation—T912
CORRECTIVE
MAINTENANCE
Corrective maintenance
consists of
repair and parts
replacement. This
section contains general
information,
troubleshooting
information, and component replace-
ment
information.
NOTE
Be
sure
you are
familiar
with the
soldering
techni-
ques and parts
replacement
procedures
before
replacing any components.
Soldering Techniques
WARNING
To prevent
electrical
shock, or damage to
the
instrument,
always disconnect the
instrument from
the
power source before
soldering.
The T900
Series
uses some
single-sided
circuit
boards,
i.e.,
wiring
is
plated on only one side.
The components
are
located on the front of the
circuit boards.
The circuit
designations have
been
silk-screened
onto the compo-
nent side
of the
circuit board
next to
the
components.
The
circuit boards
are mounted
with the
component side out to
allow access to
the
components.
If it is necessary to
replace a
component, the
leads
may be clipped
and
the
new part soldered
to
the leads
of the
previous one.
However, be
careful not to
loosen
the connection with the
etched
circuit wiring
on
the back of the circuit board.
For soldering,
use ordinary 60/40
solder and
a 15-watt
soldering
iron.
Excessive heat can
cause
the etched circuit
wiring
to
separate from
the board
base
material.
Use
caution if using a
higher
wattage-rated
soldering
iron on
the
circuit boards.
NOTE
If the instrument does
not work
after
replacing
components by
soldering
to the leads
of the
previous one,
the
connection
with
the etched circuit
wiring may be broken. To
check
the
connections,
it
is necessary to remove the
circuit board
from
the
instrument. Refer
to the
circuit board
replacement
information.
Replacement Parts
All parts for the T912 can be
ordered
from your local
Tektronix
Field
Office,
but many
of
the components
are
standard items that may be more readily
available locally.
Check the parts list for
value,
tolerance, ratings, and
description before you
replace
any components.
When
ordering parts
from
Tektronix, include the
following
information:
(1)
Instrument type.
(2)
Instrument serial number.
(3)
A
description of
part
(if
electrical, include
thecircuit
number).
(4)
Tektronix part number.
Component
Replacement
WARNING
Disconnect the
instrument from
the
power
source
before
replacing
components.
Since the
components
are located
on one
side of the
circuit boards,
it is
necessary to remove the circuit boards
before
replacing some
components. Refer to the
paragraphs on
circuit board
replacement for
instructions
in
removal
and installation of each
circuit board.
Also be
sure
you’re familiar with
soldering
techniques used on
single-sided circuit
boards.
Semiconductors
Replacement
of
semiconductors may affect the
adjust-
ment of
this instrument. After
replacing semiconductors,
especially if using parts other than
those listed
in the parts
list,
check
the performance
of
the
instrument to be sure
that the
performance
has not been degraded.
WARNING
1
Handle
silicone grease with care. Avoid
getting
silicone grease
in
the eyes. Wash hands thoroughly
after
use.
Replacement semiconductors should be
of the
original
type
or
a direct replacement. Lead
configuration
of the
semiconductors used in this
instrument
are shown in this
section. Some plastic case
transistors have lead con-
figurations
which
do
not agree with those shown
there.
If a
replacement transistor
is made by a
different
manufac-
turer than the original,
check
the manufacturer's basing
diagram
for
correct
basing. Most
transistors
are
soldered
directly onto the circuit
boards. Transistors having heat
radiators or those
mounted on the chassis use
silicone
grease
to
increase heat
transfer. Replace
the
silicone
grease when
replacing these transistors. Those tran-
sistors
mounted on the chassis are held in place by a metal
clip.
REV. A APR 1977
5-11