Delay-Line Hf Compensation (R272, R273, R275, C274, C273); Ch 3 Hf Compensation; Ch 4 Hf Compensation; Ch 1 And Ch 2 Bandwidth Check - Tektronix 2246 1Y Service Manual

Adjustment Procedure—2246 1Y and 2246 Mod A Service
b. Set calibration generator for STD AMPL. Set
amplitude to 2 V. Remove 50 f I termination.
c. ADJUST—CH 4 GAIN
4-division display amplitude.
d. Disconnect calibration generator from CH 4.
e. CHECK-MEASUREMENT BANDWIDTH and SELF
CHARACTERIZATION procedure and adjust as
necessary.
20. Delay-line HF Compensation (R272, R273,
R275, C274, C273)
a. Set:
Vertical MODE
CH 1 VOLTS/DIV
SEC/DIV
BW LIMIT
b. Connect calibration
FAST RISE OUTPUT to the CH 1 input via a 50 H
precision coaxial cable and a 50 H termination.
c. Set calibration generator for FAST RISE at 1 MHz
and adjust Pulse Amplitude for a 5-division
display.
d. Position the top of display to the center hori­
zontal graticule line.
e. ADJUST-DLY LINE COMP adjustments (R272,
R273, R275) for flattest response and (0274,
C273) for sharpest front corner with minimum
overshoot. Figure 5-1
waveform affected by each adjustment.
NOTE
It may be necessary to adjust for a small
amount of overshoot on the front corner of
the pulse in order to meet the bandwidth
check (step 23). Total overshoot and aberra­
tions must be less than 0.25 division, peak-
to-peak.
5-10
(R241) for exactly a
CH 1 (CH 4 off)
50 mV
20 ns
Off
generator positive-going
shows areas of the
Figure 5-1. Areas of waveform affected by

HF compensation.

21. CH 3 HF Compensation (C138)
a. Set:
Vertical MODE
CH 3 VOLTS/DIV
b. Move calibration generator signal to CH 3. Set
Pulse Amplitude to maximum to obtain about 2.5
division display.
c. ADJUST-C138 (CH 3 HF COMP) for flattest
response.
22. CH 4 HF Compensation (C158)
a. Set:
Vertical MODE
CH 4 VOLTS/DIV
b. Move calibration generator signal to CH 4.
c. ADJUST-C158 (CH 4 HF COMP) for flattest
response.
d. Disconnect calibration generator.

23. CH 1 and CH 2 Bandwidth Check

a. Set:
Vertical MODE
CH 1 VOLTS/DIV
SEC/DIV
b. Connect leveled sine-wave generator output to
the CH 1 input via a 50 f l precision coaxial cable
and a 50 n BNC termination.
CH 3 (CH 1 off)
0.5 V
CH 4 (CH 3 off)
0.5 V
CH 1 (CH 4 off)
5 mV
0.1 ms