Tektronix 3A74 Calibration Procedure page 5

This instrument must meet Factory Test Limits before it leaves Manufacturing;
therefore, it must be possible to inspect to these limits. Because of normal
variations in test equipment and plug-in scopes, addition of side panels, etc,
this procedure may require that some checks and adjustments be made so that
performance is better than that required by Factory Test Limits.
1. PRELIMINARY INSPECTION 8. NORM-INVERT SHIFT
Install current modifications +ldiv max
2. PRESET TYPE 3A74 9, LINE-VOLTAGE TRACE DRIFT
a. Front panel controls Check vertical drift due to changing
b. DC BAL, GAIN ADJ, all other internal line voltage 105VAC to 125VAC:
adjustments should be centered less than 0.5div
3. RESISTANCE CHECKS '10. OUTPUT AMPLIFIER
a. Check interconnecting plug resistances--- a. Setup
negative meter lead to gnd "b. Adjust CAL for 20:1 gain
b. Check protection diodes c. Check amplifier balance: within 5%
11. CH 1, 2, 3, 4 INPUT GRID CURRENT
-Set up equipment; allow 5 minutes for .
warmup Check CH 1, 2, 3, 4 input grid
currents: less than 0.2div trace
shift
5. ZENER VOLTAGE
Check +50V +5V (D494) 12. MICROPHONICS
) Check microphonics (ringing-type):
6. DC BALANCE less than 0.5div
Adjust CH 1, 2, 3, 4 DC BAL: less
than 1 minor div trace shift when 13. ALTERNATE DISPLAY
setting of VAR GAIN is changed
Check for alternate display with
2 or more channels
7. POSITION RANGE
a. Locate CRT electrical center
b. Adjust Position Range (R449): all 14. CHOPPED DISPLAY
traces less than ldiv from CRT
electrical center with POSITION a. Adjust chopped blanking signal
controls centered amplitude: 35V P-P
c. Check Output balance: within 0.2div Check CH 1 ONLY trigger noise:
300mV or less
b. Check CRT CATHODE SELECTOR switch:
switching transients blanked out
in CHOPPED BALNKING position
July 1969 3A74 5