Tektronix 5441 Instruction Manual page 92

TROUBLESHOOTING TECHNIQUES
The following troubleshooting procedure is arranged to
check the simple trouble possibilities before proceeding with
extensive troubleshooting. The first few checks ensure
proper connection, operation, and adjustment. If the trouble
is not located by these checks, the remaining steps aid in
locating the defective component. When the defective com-
ponent is located, it should be replaced using the replace-
ment procedure given under Corrective Maintenance.
Troubleshooting Procedure
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 con-
trol, see Fig. 2-1.
2. Check Associated Equipment. Before troubleshoot-
ing, check that the equipment used with this instrument is
properly connected and that the interconnecting cables are
not defective. Also, check the power source.
3. Visual Check. Visually check the portion of the instru-
ment in which the trouble is located. Many troubles can be
located by visible indications such as unsoldered connec-
tions, broken wires, damaged circuit boards, damaged com-
ponents, etc.
4. Isolate Trouble to a Circuit. To isolate trouble to a
circuit, note the trouble symptom. The symptom often iden-
tifies the circuit in which the trouble is located. When trouble
symptoms appear in more than one circuit, check the affect-
ed circuits by taking voltage and waveform readings. Incor-
rect operation of all circuits often indicates trouble in the
power supply. Check first for correct voltages of the individ-
ual supplies. See Table 5-1. However, a defective compo-
nent elsewhere in the instrument can appear as a
power-supply trouble and may also affect the operation of
other circuits.
5. Check Voltages and Waveforms. Often the defec-
tive component can be located by checking for the correct
voltages and waveforms in the circuit.
6. Check Instrument Adjustment. Check the adjust-
ment of this instrument, or the affected circuit if the trouble
appears in one circuit. The apparent trouble may be the re-
sult of misadjustment. Complete adjustment instructions are
given in Section 4.
Table 5-1
POWER SUPPLY TOLERANCES
7. Check Individual Components. The following proce-
dures describe methods for checking individual compo-
nents. Two-lead components that are soldered in place are
best checked by first disconnecting one end. This isolates
the measurement from the effects of surrounding circuitry.
Power Supply
200 V
+30 V
+15 V
-15 V
-30 V
To avoid component damage, disconnect the power
source before removing or replacing seirnconductors.
TRANSISTORS. The best check of transistor operation
is actual performance under operating conditions. A transis-
tor can be most effectively checked by substituting a new
component or one that has been checked previously. How-
ever, be sure that circuit conditions are not such that a re-
placement transistor might also be damaged. If substitute
transistors are not available, use a dynamic tester. Static-
type testers are not recommended, since they do not check
operation under simulated operating conditions.
Tolerance
+80 V to +240 V
+29.925 V to +30.075 V
+14.85Vto+15.15V
-14.85Vto-15.15V
-29.925 V to -30.075 V
INTEGRATED CIRCUITS. IC's can be checked with a
voltmeter, test oscilloscope, or by direct substitution. A
good understanding of circuit operation is desirable when
troubleshooting circuits using IC's. Use care when checking
voltages and waveforms around the IC's so that adjacent
leads are not shorted together. A convenient means of clip-
ping a test probe to the 14- and 16-pin IC's is with an IC test
clip. This device also serves as an extraction tool.
Typical
120 Hz Ripple
2 V or less
2 mV or less
2mVorless
2mVorless
2 mV or less
Do not use an ohmmeter scale that has a high internal
current. High currents may damage the diode.
REV MAY 1982