Tektronix 422, Instruction Manual

Page: 81 / 213

Maintenance—Type 422 AC-DC
fro n t o f this manual). Be sure to replace only w ith a direct
replacement Tektronix transformer.
When removing the transformer, tag the leads w ith the
corresponding terminal numbers to aid in connecting the
new transformer. A fte r the transformer is replaced check
the performance o f the complete instrument using the Per­
formance Check procedure.
High-Voltage Compartment. The components located in
the high-voltage compartment can be reached fo r 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 w ith the bottom side up.
3. Remove the tw o screws which hold the high-voltage
compartment to the chassis.
4. L ift the complete high-voltage compartment away
from the chassis.
5. Slide the shield o ff the plastic high-voltage housing.
The tw o pins on the bottom o f 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 o f 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 o f the
circuit boards and the insulator sheet.
Fig. 4-6. Location of circuit boards in high-voltage compartment.
NOTE
A ll solder joints in the high-voltage compartment
should have smooth surfaces. A ny protrusions may
cause high-voltage arcing at high altitudes.
Recalibration After Repair
A fte r any electrical component has been replaced, the
calibration o f 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
o f the entire instrument should be checked if w ork has
been done in the low-voltage supply or if the power trans­
form er has been replaced. The Performance Check proce­
dure provides a quick and convenient means o f checking
instrument operation.
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