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Maintenance— 2236 Service
TRANSISTORS AND INTEGRATED
CIRCUITS
Transistors and integrated circuits should not be re
placed unless they are actually defective. If unsoldered from
the circuit board during routine maintenance, return them to
their original board locations. Unnecessary replacement or
transposing of semiconductor devices may affect the adjust
ment of the instrument. When a semiconductor is replaced,
check the performance of any instrument circuit that may be
affected.
Any replacement components 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 for typical lead-
configuration illustrations.
To remove a soldered dual-in-line packaged (DIP) 1C, do
not heat adjacent conductors consecutively. Apply heat to
pins at alternate sides and ends of the 1C as solder is re
moved. Allow a moment for the circuit board to cool before
proceeding to the next pin.
The heat-sink-mounted power supply transistors are in
sulated from the heat sink. In addition, a heat-sink com
pound is used to increase heat transfer capabilities.
Reinstall the insulators and replace the heat-sink compound
when replacing these transistors. The compound should be
applied to both sides of the insulators and should be applie
to the bottom side of the transistor where it comes in cor
tact with the insulator.
NOTE
After replacing a power transistor, check that the col
lector is not shorted to the heat sink before applying
power to the instrument.
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
instrument.
W A R N I N G
To avoid an electric-shock hazard, observe the follow
ing precautions before attempting any soldering: turn
the instrument off, disconnect it from the ac power
source, and allow approximately three minutes for the
power-supply capacitors to discharge.
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 circuit boards or small insulated
wires, use only a 15- to 25-watt, pencil-type soldering iron.
A higher wattage soldering iron can cause etched-circuit
conductors to separate from the board base material and
melt the insulation on small wires. Always keep the solder
ing-iron tip properly tinned to ensure best heat transfer from
the iron tip to the solder joint. To protect heat-sensitive
components, either hold the component lead with long-nose
pliers or place a heat block between the component body
and the solder joint. Apply only enough solder to make a
firm joint. After soldering, clean the area around the solder
connection with an approved flux-removing solvent (such as
isopropyl alcohol) and allow it to air dry.
C A U T I O N
Attempts to unsolder, remove, and resolder leads
from the component side of a circuit board may cause
damage to the reverse side of the circuit board.
The following techniques should be used to replace a
component on any of the circuit boards:
1.
Touch the vacuum desoldering tool to the lead at the
older connection. Never place the iron directly on the
Doard; doing this may damage the board.
NOTE
Some components are difficult to remove from the cir
cuit board due to a bend placed in each lead during
machine insertion of the component. The purpose of
the bent leads is to hold the component in place dur
ing a solder-flow manufacturing process that solders
all the components at once. To make removal of ma
chine-inserted components easier, straighten the
component leads on the reverse side of the circuit
board with a small screwdriver or pliers. It may be
necessary to remove the circuit board to gain access
to the component leads on the reverse side of the
circuit board. Circuit-board removal and reinstallation
procedures are discussed later in this section.
2.
When removing a multipin component, especially an
1C, do not heat adjacent pins consecutively. Apply heat to
pins at alternate sides and ends of the 1C as solder is re
moved. Allow a moment for the circuit board to cool before
proceeding to the next pin.
6-24
Содержание 2236
Страница 10: ...2236 Service viii The 2236 Oscilloscope ...
Страница 28: ...Specification 2236 Service 1 18 ADD JAN 1985 Figure 1 2 Physical dimensions of the 2236 Oscilloscope ...
Страница 74: ...Theory of Operation 2236 Service 3 30 ...
Страница 75: ...Theory of Operation 2236 Service Figure 3 13 Typical waveforms for the Delta Time function with Valt HI 3 31 ...
Страница 102: ...Performance Check Procedure 2236 Service 4 21 Figure 4 1 Test setup for DMM common mode check ...
Страница 240: ...2236 Service CTM INTERFACE SIGNALS F ig u re 9 4 O s c illo s c o p e b a sic b lo c k diag ram 4294 46 ...
Страница 241: ... VERT DEFL 2236 Service 4 2 0 6 3 5 4 2 0 4 4 7 F ig u re 9 5 O scillo sco p e d e ta ile d b lo c k diag ram ...
Страница 242: ...2236 Service 4204 34 Figure 9 6 CTM basic block diagram ...
Страница 243: ...DMM POWER S U P P LIE S 2236 Service F ig u re 9 7 C T M d e ta ile d b lo c k diag ram ...
Страница 253: ...A10 COUNTER TIMER MULTIMETER BOARD F ig u re 9 8 C irc u it b o a rd lo c a tio n Illu s tra tio n ...
Страница 254: ...S I 0 O I 5 1 S O i 4204 21 C IR C U IT BOARD INTERCONNECTIONS ...
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Страница 319: ...2236 Service TROUBLESHOOTING GUIDE 4206 99 4204 69A ...
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