Maintenance—Type 422 AC-DC
front of this manual). Be sure to replace only with a direct
replacement Tektronix transformer.
When removing the transformer, tag the leads with the
corresponding terminal numbers to aid in connecting the
new transformer. After the transformer is replaced check
the performance of the complete instrument using the Per
formance Check procedure.
High-Voltage Compartment. The components located in
the high-voltage compartment can be reached for mainten
ance or replacement by using the following procedure.
1. Remove the cabinet from the instrument as described
earlier in this section.
2. Turn the instrument over with the bottom side up.
3. Remove the two screws which hold the high-voltage
compartment to the chassis.
4. Lift the complete high-voltage compartment away
from the chassis.
5. Slide the shield off the plastic high-voltage housing.
The two pins on the bottom of the housing must be freed
from the holes in the shield before the shield can be slid
off.
6. Remove the lid of the high-voltage housing.
7. To replace the high-voltage compartment, reverse the
order of removal. When placing the circuit boards back into
the compartment, be sure the insulator sheet is installed in
the proper place. Fig. 4-6 shows the correct location of the
circuit boards and the insulator sheet.
Fig. 4-6. Location of circuit boards in high-voltage compartment.
NOTE
All solder joints in the high-voltage compartment
should have smooth surfaces. Any protrusions may
cause high-voltage arcing at high altitudes.
Recalibration After Repair
After any electrical component has been replaced, the
calibration of that particular circuit should be checked, as
well as the calibration of other closely related circuits.
Since the low-voltage supply affects all circuits, calibration
of the entire instrument should be checked if work has
been done in the low-voltage supply or if the power trans
former has been replaced. The Performance Check proce
dure provides a quick and convenient means of checking
instrument operation.
4-13
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