Maintenance—2465B/2467B Service
holders. If the connectors are faulty, the entire wire
assembly should be replaced.
Multipin Connectors
When pin connectors are grouped together and
mounted in a plastic holder, they are removed, reinstalled,
or replaced as a unit. If any individual wire or connector in
the assembly is faulty, the entire cable assembly should be
replaced.
Multipin connector orientation is indexed by a
tri-
angle on the cable connector and a 1 or triangle on the cir-
cuit board. Slot numbers may be molded into the
connector. Be sure these index marks are aligned with
each other when the multipin connector is reinstalled.
TRANSISTORS, INTEGRATED CIRCUITS,
AND HYBRID CIRCUITS
Transistors, integrated circuits, and hybrid circuits
should not be replaced unless they are actually defective.
If removed from their sockets or unsoldered from the cir-
cuit board during routine maintenance, return them to their
original board locations. Unnecessary replacement or
transposing of semiconductor devices may affect the
adjustment of the instrument. When a semiconductor is
replaced,
check the performance of any circuit that may be
affected.
Any replacement component should be of the original
type or a direct replacement. Bend transistor leads to fit
their circuit board holes, and cut the leads to the same
length as the original component. See Figure 9-2 in the
"Diagrams" section for lead-configuration illustrations.
The heat-sink-mounted power supply transistors are
insulated from the heat sink with a heat-transferring
insu-
lator pad. Reinstall the insulator pads and bushings when
replacing these transistors. Do not use any type of heat-
transferring compound on the insulator pads.
After replacing a power transistor, check that the
collector is not shorted to the heat sink before
apply-
ing power to the instrument.
To remove socketed dual-in-line packaged (DIP)
integrated circuits, pull slowly and evenly on both ends of
the device. Avoid disengaging one end of the integrated
circuit from the socket before the other, since this may
damage the pins.
To remove a soldered DIP IC when it is going to be
replaced,
clip all the leads of the device and remove the
leads from the circuit board one at a time. If the device
must be removed intact for possible reinstallation, do not
heat adjacent conductors consecutively. Apply heat to pins
at alternate sides and ends of the IC as solder is removed.
Allow a moment for the circuit board to cool before
proceeding to the next pin.
Hybrid circuits and heatsinks are removed as a unit by
removing the mounting nuts at the four corners of the
heatsink/housing. A firm downward pressure at the center
of the heatsink will aid in installation/removal of the nuts.
The hybrid circuit substrate is bonded to the
heatsink/housing casting. Attempting to separate the
hybrid device from its heatsink will damage the device.
SOLDERING TECHNIQUES
The reliability and accuracy of this instrument can be
maintained only if proper soldering techniques are used to
remove or replace parts. General soldering techniques,
which apply to maintenance of any precision electronic
equipment, should be used when working on this instru-
ment.
WARNING
To avoid an electric-shock hazard, observe the
fol-
lowing precautions before attempting any soldering:
turn the instrument off, disconnect it from the ac
power source, and verify that the line-rectifier filter
capacitors have discharged (see label on the primary
power shield). If, due to a component failure, the
capacitors are not discharging, it may be necessary
to discharge them. Use a 1-kft
5-watt
resistor and
discharge the capacitors from point to point through
the access holes in the primary power shield.
Use rosin-core wire solder containing 63% tin and 37%
lead.
Contact your local Tektronix Field Office or represen-
tative to obtain the names of approved solder types.
When soldering on circuits boards or small insulated
wires,
use only a 15-watt, pencil-type soldering
iron.
A
higher wattage soldering iron may cause etched circuit
conductors to separate from the board base material and
melt the insulation on small wires. Always keep the
soldering-iron tip properly tinned to ensure best heat
transfer from the iron tip to the solder joint. Apply only
enough solder to make a firm joint. After soldering, clean
the area around the solder connection with an approved
6-22
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