Power Supply; Check/Adjust Low-Voltage Supply; Check/Adjust High-Voltage Supply; Check/Adjust Grid Bias - Tektronix 221 Instruction Manual

Calibration—221 Service
Equipment Required
1. Digital voltmeter
2. Variable auto transformer
Control Settings
Preset the controls as given in the Preliminary Control
Setting.

1. Check/Adjust Low-voltage Supply

a. Connect the digital voltmeter from the —5 volt test
point to the +5 volt test point.
b. Use the variable auto transformer and 1:2 power
step-up transformer to provide a 90 to 250 Vac line source.
Connect the 221 oscilloscope to the line.
c. Check for a reading of 10 volts from a 90 to 250 Vac
line.
d. Adjust R644 Low Voltage adjustment for exactly
10 volts. See Fig. 5-1.
e. Connect the common lead of the digital voltmeter to
the 0 volt test point.
f. Check the +5 volt supply for +5 volts ±50 mV
2.

Check/Adjust High-voltage Supply

a. Connect the digital voltmeter to the 1 kV test point.
b. Check fo r a reading of —1000 volts.
5-4

POWER SUPPLY

3. 1:2 power step-up transformer
4. Three-inch screwdriver
c. Adjust the High Voltage adjustment R662 for exactly
—1000 volts. See Fig. 5-1.
3.

Check/Adjust Grid Bias

a. Connect the digital voltmeter to the 0.2 volt test
point.
b. Rotate the
position.
c. Check the digital voltmeter fo r a reading of 0.2 volt
±0.02 volt.
d. Adjust Grid
0.2 volt. See Fig. 5-1
4. Check +48-volt and +75-volt Supplies
a. Connect the digital voltmeter from the 0 volt test
point to the +48-volt test point (leave INTENSITY fu lly
clockwise fo r remainder of Step 4).
b. Check fo r a minimum of +48 volts.
c. Connect the digital voltmeter from the 0-volt test
point to the +75 volt test point.
d. Check fo r a minimum of +75 volts.
e. Set INTENSITY as desired for normal viewing in
Step 5.
INTENSITY to the fu lly clockwise
Bias Adjustment R739 fo r exactly
REV B, MAY 1978