Maintenance—Type 422 AC-DC
Emitter
Metal-Case Transistors
Plastic-Case Transistors
Dual Field-
Effect Transistor Power Transistors
Fig. 4-3. Electrode configuration for transistors in this instrument (as viewed from bottom).
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 fol
lowing the replacement procedures 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.
2. Check Associated Equipment. Before proceeding
with troubleshooting of the Type 422, check that the
equipment used with this instrument is operating correctly.
Check that the signal 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
instrument in which the trouble is located. Many troubles
can be located by visual indications such as unsoldered con
nections, broken wires, damaged circuit boards, damaged
components, etc.
4. Check Instrument Calibration. Check the calibration
of this instrument, or the affected circuit if the trouble
appears in one circuit. The apparent trouble may only be a
result of misadjustment or may be corrected by calibration.
Complete calibration instructions are given in the Calibra
tion section.
5. Isolate Trouble to a Circuit. To isolate trouble to a
circuit, note the trouble symptom. The symptom often
identifies the circuit in which the trouble is located. For
example, poor focus indicates that the CRT circuit
(includes high voltage) is probably at fault. When trouble
symptoms appear in more than one circuit, check affected
circuits by taking voltage and waveform readings.
Incorrect operation of all circuits often indicates trouble
in the power supply. Check first for correct voltage of the
individual supplies. However, a defective component else
where in the instrument can appear as a power-supply
trouble and may also affect the operation of other circuits.
Table 4-3 lists the tolerances of the power supplies in this
instrument. If a power-supply voltage is within the listed
tolerance, the supply can be assumed to be working cor
rectly. If outside the tolerance, the supply may be misad-
justed or operating incorrectly. Use the procedure given in
the Calibration section to adjust the power supplies.
TABLE 4-3
Power Supply Tolerance and Ripple
Power
supply
Tolerance
Maximu
(peak t(
Line
frequency
m ripple
d peak)
High
frequency
(8 kHz)
—81 volt
—80 to —82 volts
20 millivolts
8 millivolts
-1 2 volt
—11.9 to —12.1 volts
20 millivolts
8 millivolts
+10.5 volt
+10.3 to +10.7 volts 1 millivolt
1 millivolt
+12 volt
+11.7 to +12.3 volts 20 millivolts
8 millivolts
+55 volt
+53.9 to +56.7 volts 0.32 volt
—
+95 volt
+93.1 to +97.9 volts 0.4 volt
—
Fig. 4-4 provides a guide for locating a defective circuit.
This chart may not include checks for all possible defects;
use steps 6 through 8 in such cases. Start from the top of
the chart and perform the given checks on the left side of
the page until a step is found which does not produce the
indicated results. Further checks and/or the circuit in which
the trouble is probably located are listed to the right of this
step.
4-5
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