Tektronix T921 User Manual

Service
Information-T921/T92 2/T922R
solution of one part Kelite to 20 parts water . If these arenot
available,
petroleum ether, white kerosene, or a solution of
1% Joy detergent and 99% water
may be used .
Recommended circuit coolants are dry ice and
isopropyl alcohol
.
The cam switch contacts are designed to operate
without lubrication . They do require cleaning periodically
to remove accumulations of dust and dirt . The use of
lubricants or cleaners that leave a residue, increase dust
attraction and should be avoided
.
Visual Inspection
Inspect the interior occasionally for broken connec-
tions, improperly seated semiconductors, damaged or
improperly installed circuit boards, heat damaged com-
ponents, etc . If heat damaged components arefound, care
mustbe taken to find the cause of the excessive heat and
measures
must be taken to prevent recurrence of the
damage .
Lubrication
Most of the potentiometers are permanently sealed .
Both the cam- and lever-type
switches are installed with
proper lubrication where necessary . Therefore
periodic
lubrication is not recommended and only rarely should
lubrication even be necessary .
Semiconductor Checks
Periodic checks of the semiconductor devices in this
instrument are not recommended . The best check of
semiconductorperformance is actual operation in the
instrument .
Re-adjustment
Re-adjust the
instrument whenever the Performance
Check indicates the
instrument is not meeting
specifications . The Performance
Check should be per-
formedon a regular basis ; for example, every 1000
hours
of operation or every six months .
If you perform preventive maintenance
on a regular
basis, you should correct most problems before your
instrument breaks down . Occasionally, you may have to
troubleshoot . In
addition tothe following information, you
may find information in the
Circuit Description and
Diagrams section useful .
5-2
TROUBLESHOOTING
Troubleshooting Aids
Troubleshooting Chart . Use the troubleshooting chart
(Fig . 5-1) to locate problem areas .
Diagrams . Complete circuit diagrams are
located on
thefoldout pages in the Circuit Description and Diagrams
section . The componentnumber and electrical value of
each component in the instrument are shown on the
diagrams (see the first page of the Diagrams section for
the definitions of the reference designators used to
identify components) . Each main circuit is assigned a
series of component numbers to assist in identifying their
circuit location . Important
voltages andwaveforms are
also shown on the diagrams . Also a heavy line encloses
the portion of the circuit mounted on a circuit board .
Color Codes . The resistors
used
in this instrument are
either brown composition or precision metal-film
resistors . The resistors are color-coded with the EIA color-
code . (Some metal-film resistors may have the value
printed on the body .) Refer to Fig . 5-2 . For the values of the
thick film
resistors, refer to the Parts List .
The capacitance values of common disc and some
small electrolytic capacitors are markedon the side of the
component body . The white ceramic capacitors are color-
coded, using a modified EIA code . (See Fig . 5-2) .
The cathode end of each glass-encased diode
is
indicated by a stripe, a series of stripes, or a dot .
Semiconductor Lead Configuration . Fig . 5-3 shows the
lead
configuration of the semiconductor devices used in
this instrument .
Troubleshooting Equipment
Multi-connector Holders . The multi-connector holder
is keyed
with
two triangles, one on the holder andone on
the circuit board . When a connection
is made perpen-
dicular to a circuit board surface, the orientation of the
triangle and the slot numbers on the connector holder are
determined by the direction of the nomenclature marking
(see Fig . 5-4) .
The following equipment is useful for troubleshooting .
1 . Semiconductor Tester
Description : Dynamic-type tester . Must be capable .
of measuring reverse breakdown voltages of at least
400 V
.
REV . A JUN 1976

Tektronix T921 Specifications

General

Brand	Tektronix
Model	T921
Category	Test Equipment
Language	English