TM 11-6625-2735-14-1
1. Semiconductor Tester
Description: Dynamic
— type tester. Must be capable of
measuring reverse breakdown voltages of at least
400 volts.
Purpose: To test the semiconductors used in this
instrument.
Recommended type: Tektronix 576 Curve Tracer or
Tektronix 577 (D1 or D2) Curve Tracer with 177 Test
Fixture.
2. Test Oscilloscope
Description: Frequency response, dc to 75 megahertz
or greater; deflection factor, 1 millivolt to 5 volts/division;
Input impedance, 1 megohm, 20 picofarads; sweep rate,
0.5 second/division to 50 nanoseconds/division. A 10X,
10-megohm voltage probe should be used to reduce
circuit loading for waveform measurements. A 1X, 1-
megohm voltage probe should be used for power supply
ripple checks.
Purpose: To check operating waveforms in this instru-
ment.
Recommended type: Tektronix 7603 Oscilloscope with
7A13 Amplifier and 7650 Time-Base units. Use a P6053
10X probe and a P6011 1X probe.
3. Multimeter
Description:
Non-loading
Digital Multi meter.
Voltmeter, 10 megohm input impedance and 0 to 150 volts
range; dc voltage accuracy, within 0.15%; display, 4-1/2
digits. Ohmmeter,
0 to 20 megohms.
Purpose: To check voltages and for general
troubleshooting in this instrument.
Recommended type: Tektronix DM 501 Digital Multi-
meter (requires a TM 500-series power module).
4. Variable Autotransformer
Description: Output variable from
0 to 140 volts, 1.2
amperes minimum rating. Must have 3-wire power cord,
plug, and receptacle.
Purpose: To vary the input line voltage when
troubleshooting in the power supply.
Recommended type: General Radio W8MT3VM or
W10MT3W Metered Variac Autotransformer.
Troubleshooting Techniques
This troubleshooting procedure is arranged in an order
which checks the simple trouble possibilities before
proceeding with extensive troubleshooting. The first few
checks ensure proper connection, operation and calibra-
tion. If the trouble is not located by these checks, the
remaining steps aid in locating the defective component.
When the defective component is located, it should be
replaced following the replacement procedure given
under Corrective Maintenance.
1. Check Control Settings. Incorrect control settings
can indicate a trouble that does not exist. If there is any
question about the correct function or operation of any
control, see the Operating Instructions section of this
manual.
2. Check Associated Equipment. Before proceeding
with troubleshooting of the 475, check that the equipment
used with this instrument is operating correctly. Check
that the signal is properly connected and that the inter-
connecting cables are not defective. Also, check the
power source.
3. Check Instrument Calibration. Check the calibra-
tion of this instrument, or the affected circuit if the trouble
exists in only one circuit. The apparent trouble may only
be a result of misadjustment and may be corrected by
calibration. Complete calibration instructions are given in
the Calibration section of this manual.
4. Visual Check. Visually check the portion of the
instrument in which the trouble is located. Many troubles
can be located by visual indications such as unsoldered
connections, broken wires, damaged circuit boards,
damaged components, etc.
5. Isolate Trouble to a Circuit. To isolate trouble to a
particular circuit, note the trouble symptom. The symptom
often identifies the circuit in which the trouble is located.
When trouble symptoms appear in more than one circuit,
check affected circuits by taking voltage and waveform
readings. Typical voltages and waveforms are given on the
schematics in the Diagrams section.
6. Circuit Troubleshooting Sequence. If the instru-
ment is found to have inoperative functions in more than
one area of the main oscilloscope circuits, repair the
circuits in the order specified in the following list.
a. L.V POWER SUPPLY (Check +50 V, +110 V,
+15 V, +5V,
—15 V and –8 V supplies.)
4-10
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