Tektronix 2A60 Instrument Reference Book page 29

Type 2A60 Amplifier
C404C C405C C405B C404B
INt. TRIG. HUM C411 C403C C403B
DC LEVEL BAL.
Fig. 4. Type 2A60 module calibration adjustments.
Equipment Required
The following equipment is required to calibrate the Type
2A60 Amplifier module:
1. Square-wave generator with a risetime of 0.35 micro-
second or less and a frequency of 1 kc or less. (You may
use the Calibrator output if a square-wave generator is
not available. See "Attenuator Frequency Compensation",
step 2.)
2. 47-pf capacitance standardizer (Tektronix Type CS
47 recommended), or a capacitance meter and an attenu-
ator probe.
3. De Voltmeter.
Internal Trigger
De
Level Adjustment
The need for adjustment of the internal trigger de level
is generally indicated by triggering difficulties with a time-
base module set for internal de triggering of the sweep. To
properly adjust the internal trigger de level, proceed as
follows:
1. Set the AC-DC-GND. switch to GND. and the VARI-
ABLE control fully clockwise (to the CALIBRATED position).
2. Center the spot or trace on the screen.
3. Set the INT. TRIG. DC LEVEL adjustment so that the
potential at pin 11 of the plug-in connector is exactly zero
with respect to ground.
®!
Hum Balance Adjustment
The need for hum balance adjustment is indicated by the
presence of excessive 60-cps ripple on the trace. To prop-
erly adjust for hum balance in the Type 2A60 module,
proceed as follows:
1. Set the AC-DC-GND. switch to AC, the VOLTS/DIV.
switch to .05, and the VARIABLE control fully clockwise (to
the CALIBRATED position).
2. Display a no-signal trace on the screen (preferably
triggered at line frequency).
3. Shield the INPUT connector (this can be done by
placing a small flat piece of metal, such as a coin, over
the face of the connector), and set the FOCUS and
INTENSITY controls for the sharpest trace possible.
4. Adjust the HUM BAL. adjustment to minimize any
line-frequency ripple on the trace.
Input Capacitance Standardization and Attenu-
ator Frequency Compensation
The input capacitance standardization and attenuator
frequency compensation interact, so both are performed
in the same procedure. The need for either or both of these
calibrations is normally indicated by distortion of fast-
rising waveforms on one or more sensitivity ranges of the
module. Standardization of the input capacitance of the
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