Tektronix 323, Instruction Manual

Page: 60 / 170

Maintenance— Type 323
Some diodes used in the Type 323 Oscilloscope are color
coded to identity the diode type. A blue or pink first band
indicates that the next three colors translate to the last
three digits of its part number. Diode polarity can be de­
termined by color code position. See Fig. 4-1.
Fig. 4 -1 . Diode color code rela ted to p a rt number and conducting
p o la rity.
NOTE
The positive side o f an ohmmeter voltage source is
often connected to the meter common test lead.
J g i
— ls t Sig. Fig.
— 2 nd Sig. Fig.
r — 3rd Sig. Fig.
1
— M u ltip lie r
r — Tolerance
- -----
Date Code
i lst
Color Sig.
Fig.
2nd
Sig.
Fig. 3rd
Sig.
Fig. Multiplier
Tolerance
(±1 %
Black 0 0 0 1
—
Brown 1 1 1 10
1
Red 2 2
2
100
2
Orange 3 3 3
1,000 —
Yellow 4 4 4 10,000 —
Green 5 5 5 100,000
0.50
Blue 6 6 6
1,000,000 0.25
Violet 7 7 7 10,000,000
0.10
Gray 8 8 8
100,000,000 0.05
White
9 9 9 1,000,000,000 —
Gold 0.1
5
Silver 0.01
—
No Color
10
Resistors. The same ohmmeter voltage and current pre­
cautions observed in transistors troubleshooting also apply
when making in-circuit resistance checks. Because semi-con­
ductor devices are present, most resistors in the Type 323
must be disconnected before reliable resistor checks can be
made.
The types of resistors found in this instrument vary in
accordance with the circuit needs. Composition, metal film
and wire-wound resistors are used. Replacement resistors
should be of the same type and must be at least as accu­
rate as those originally contained in the circuit to main­
tain performance standards. The size, location and lead
length are often critical because of frequency considerations.
Resistor values are indicated by one of three methods in
the Type 323 Oscilloscope:
3 color bands (digit, digit, multiplier— tolerance)
4 color bands (digit, digit, digit, multiplier— tolerance)
Numbers printed on wire wound and metal film re­
sistors
The first two methods translate to the IEEE color-code
equivalent and are illustrated in Fig. 4-2.
W iring Inform ation. Insulated wires in the Type 323
Oscilloscope are color coded to make wire tracing easier.
When it is necessary to disconnect several wires from com­
ponents, record the wire color coding. In case of doubt in
Fig. 4 -2 . Resistor color coding.
reconnecting wires, use an ohmmeter to insure selection of
the proper lead.
Switches. Rotary switch wafers are coded with a number
and a letter on the schematic diagrams. The number indi­
cates the wafer position in the switch assembly, counting
from the front (mounting end). The letters "F" and "R" indi­
cate whether the front or rear of the wafer performs the
switching action. For example, a switch section designated
2R is contained on the rear of the second wafer as viewed
from the front of the switch.
In addition, each wafer contact is numbered as follows:
VOLTS/DIV switch and TRIGGER switch—Contacts are
numbered from 1 through 12, starting at the lower mount­
ing post and counting clockwise when viewed from the
front and counterclockwise when viewed from the rear.
TIME/DIV switch— Contacts are numbered from 1
through 18, starting at the upper mounting post and count­
ing clockwise when viewed from the front and counterclock­
wise when viewed from the rear.
Individual switch wafers or mechanical parts of rotary
switches are normally not replaced. If a switch is defective,
replace the entire assembly. Wired and unwired replace­
ment switches are available; refer to the Parts List for part
numbers. When a switch is removed, make careful nota­
tion of the lead connections for installation reference.
@i
4-4