Tektronix 485, Instruction Manual

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Maintenance—485/R485 Service
number. The circuit boards are also outlined on the
diagrams with a blue line to show which portions of the
circuit are located on a circuit board.
Wiring Color-Code. A ll insulated wire and cable used in
the 485 is color-coded to facilitate circuit tracing. Table 4-2
gives the wiring color-code used in this instrument.
W A R N I N G
This co lo r code applies to leads w ith in the 485 only.
C olor code o f the A C pow er cord is:
Black Line
White N eutral
Green Safety earth (ground)
TABLE 4-2
Wiring Color Code
Supply or
Function
Background
Color Stripe1
+ 15 volts
Red Yellow
+9 volts Red Orange
+5.5 volts
Red Brown
+5.0 volts Red Black
-5 .0 volts Violet Black
—5.5 volts Violet Red
—9 volts Violet Orange
— 15 volts Violet Yellow
Other power supply voltages are conducted by the comb
connectors.
Semiconductor Lead Configuration. Fig. 4-1 shows the
lead configuration for the semiconductors used in this
instrument. This view is as seen from the bottom of the
semiconductors.
1 If more than one stripe appears on lead, extra stripes are for lead
identification only (for circuit tracing).
Troubleshooting Equipment
The following equipment is useful for troubleshooting
the 485.
1. Transistor Tester
Description: Dynamic-type tester. Must be capable of
measuring reverse breakdown voltages of at least 400 volts.
Recommended type: Tektronix Type 576
T ransistor-Curve T racer.
2. Multimeter
Description, 10 megohm input impedance and 0 to 500
volts range, AC and DC; ohmmeter, 0 to 50 megohms.
Accuracy, w ithin 3%. Test probes must be insulated to
prevent accidental shorting.
NOTE
A 20,000 ohm s/volt VOM can be used to check the
voltages in this instrum ent i f allowances are made for
the circ u it loading o f the VOM a t high-impedance
points.
3. Test Oscilloscope
Description: Frequency response, DC to 100 megahertz
minimum; deflection factor, 5 millivolts to 5 volts/division.
Purpose: To check operating waveforms in this instru­
ment.
4. Isolation Transformer
Description: 1:1 turns ratio, 300 volt-amperes minimum
rating, 50-60 cycle. Must have three-wire power cord, plug,
and receptacle with ground connection carried through
from input to output.
Purpose: To isolate the 485 from the line potential when
troubleshooting in the power supply.
Recommended type: Stancor #P6298 (for 115-volt line
only) modified to include three-wire power cord, plug, and
receptacle.
REV. B. AUG. 1975
4-5