Troubleshooting; Troubleshooting Aids - Tektronix 7B70 Time Base Instruction Manual

Maintenance-7B7O (SN B205000 and Up)
TROUBLESHOOTING
Introduction
The following information is provided to facilitate
troubleshooting of the 7B70. Information contained in
other sections of this manual should be used along with the
following information to aid in locating the defective com-
ponent. An understanding of the circuit operation is very
helpful in locating troubles. See the Circuit Description sec-
tion for complete information.
Troubleshooting Aids
Diagrams. Circuit diagrams are given on foldout pages in
Section 7. The component number and electrical value of
each component in this instrument are shown on the
diagrams. Important voltages and waveforms are also shown
on the diagrams.
Switch Cam Identification. Switch cam numbers shown
on the-diagrams indicate the position of the cam in the
complete switch assembly. The cams are numbered from
the front, or mounting end of the switch, toward the rear.
Resistor Color-Code. In addition to the brown composi-
tion resistors, some metal-film resistors and some wire-
wound resistors are used in the 7B70. The resistance values
of wire-wound resistors are printed on the body of the
component. The resistance values of composition resistors
and metal-film resistors are color-coded on the components
(some metal-film resistors may have the value printed on
the body) with EIA color code. The color code is read
starting with the stripe nearest the end of the resistor. Com-
position resistors have four stripes which consist of two
significant figures, a multiplier and a tolerance value (see
Fig. 4-1). Metal-film resistors have five stripes consisting of
three significant figures, a multiplier and a tolerance value.
Capacitor Marking. The capacitance values of common
disc capacitors and small electrolytics are marked in micro-
farads on the side of the component body. The white
ceramic capacitors used in the 7870 are color coded in
picofarads using a modified EIA code (see Fig. 4-1).
Diode Color Code. The cathode end of each glass-
encased diode is indicated by a stripe, a series of stripes or a
dot. For most silicon or germanium diodes with a series of
Composition Resistors:
Metal-Film Resistors:
Ceramic Capacitors:
@
and
@
-,st,
2nd and 3rd significant figures;
*For capacitance of 10 pF or less.
-temperature coefficient.
Fig. 4-1. Colorcode for resistors and ceramic capacitors.
Scans by ArtekMedia O 2006