Tektronix 3B5, Instruction Manual

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Maintenance—Type 3B5
8. Check Individual Components. The following proce­
dures describe methods of checking indivdual components
in the Type 3B5. Components which are soldered in place
can be checked most easily by disconnecting one end. This
eliminates incorrect measurements due to the effects of
surrounding circuitry.
A. TRANSISTORS AND NUVISTORS. The best check of
transistor or nuvistor operation is actual performance under
operating conditions. If a transistor or nuvistor is suspected
of being defective, it can best be checked by substituting a
new component or one which has been checked previously.
However, be sure that circuit conditions are not such that a
replacement transistor or nuvistor might also be damaged.
If substitute transistors or nuvistors are not available, use
a dynamic tester (such as Tektronix Type 570 or 575). Static­
type testers are not recommended, since they do not check
operation under simulated operating conditions.
B. DIODES. A diode can be checked for an open or
shorted condition by measuring the resistance between ter­
minals. With an ohmmeter scale having an internal source
of about 1.5 volts, the resistance should be very high in one
direction and very low when the leads are reversed.
CAUTION
Do not use an ohmmeter scale that has a high
internal current. High currents may damage the
diode. Do not measure tunnel diodes or the special
clip-in diode (sweep disconnect diode) with an
ohmmeter; use a dynamic tester (such as a Tek­
tronix Type 575 Transistor-Curve Tracer). The
clip-in diode can also be damaged by static-dis-
charge.
C. RESISTORS. Resistors can be checked wih an ohm­
meter. Check the Electrical Parts List for the tolerance of
the resistors used in this instrument. Resistors normally do
not need to be replaced unless the measured value is in
excess of the specified tolerance.
D. INDUCTORS. Check for open inductors by checking
continuity with an ohmmeter. Shorted or partially shorted
inductors can usually be found by checking the waveform
response when high-frequency signals are passed through
the circuit. Partial shorting often reduces high-frequency
response (roll-off).
E. REED-DRIVE COILS. The reed-drive coils can be checked
for correct operation as follows (the coils have four mounting
leads for rigidity; make measurements between the two
leads on either end of the coil): 1) Check the DC resistance
of the coil with an ohmmeter (protective diodes are con­
nected across the coils; take diodes and other circuitry into
account on resistance measurements,- typical resistance values
are given in the Electrical Parts List). 2) Check the DC voltage
drop across the coil when the actuating level is applied.
3) If both the resistance and voltage are correct, the coil
can be assumed to be correct; check the reed relay position
and continuity. 4) If the resistance is incorrect (take into
account surrounding circuitry), disconnect the coil and check
the resistance again. 5) If the voltage across the coil is
incorrect but the coil resistance is correct, check the circuit
originating the actuating level.
F. CAPACITORS. A leaky or shorted capacitor can best
be detected by checking resistance with an ohmmeter on
the highest scale. Do not exceed the voltage rating of the
capacitor. The resistance reading should be high after initial
charge of the capacitor. An open capacitor can best be
detected with a capacitance meter or by checking whether
the capacitor passes AC signals.
9. Repair and Readjust the Circuit. If any defective
parts are located, follow the replacement procedures which
follow. Be sure to check the performance of any circuit
that has been repaired or has
had electrical
components
replaced.
CORRECTIVE MAINTENANCE
General
Corrective maintenance consists of component replacement
and instrument repair. Special techniques required to replace
components in this instrument are given here.
Obtaining Replacement Parts
Standard Parts. All electrical and mechanical part
replacements for the Type 3B5 can
be
obtained through your
local Tektronix Field Office or representative. However,
many of the standard electronic components can be obtained
locally in less time than is required to order them from
Tektronix, Inc. Before purchasing or ordering replacement
parts, check the parts lists for value, tolerance, rating and
description.
NOTE
When selecting replacement parts, it is important
to remember that the physical size and shape of
a component may affect its performance in the
instrument, particularly at high frequencies. All
replacement parts should be direct replacements
unless it is known that a different component will
not adversely affect instrument performance.
Special Parts. In addition to the standard electronic
components, some special parts are used in the Type 3B5.
These parts are manufactured or selected by Tektronix, Inc.
to meet specific performance requirements, or are manu­
factured for Tektronix, Inc. in accordance with our specifi­
cations. These special parts are indicated in the parts list
by an asterisk preceding the part number. Most of the
mechanical parts used in this instrument have been manu­
factured by Tektronix, Inc. Order all special parts directly
from your local Tektronix Field Office or representative.
Ordering Parts. When ordering replacement parts from
Tektronix, Inc., include the following information:
1. Instrument Type.
2. Instrument Serial Number.
3. A description of the part (if electrical, include circuit
number).
4. Tektronix Part Number.
Soldering Techniques
WARNING
Disconnect the instrument from the power source
before soldering.
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