Tektronix TYPE Z PLIG-IN, Instruction Manual

Page: 28 / 55

Calibration — Type Z
connectors. Make certain the VAR. ATTEN. control is set
fully clockwise. Set the G A IN ADJUST control (R8639) to
obtain exactly 4 cm of vertical deflection. Place the Mode
switch to — B O N LY. Check to see that there are exactly 4
cm of vertical deflection.
8. O perational Checks
Perform the following Z Unit operational checks:
(a) Disconnect the calibrator signal from the input con­
nectors. Check to see that the baseline does not shift
more than 2 mm after switching the Mode switch from
A O N LY to — B O N LY. Reconnect the calibrator signal
to the input connectors.
(b) With the Mode switch at — B O N LY, check the opera­
tion of the B AC-DC switch by setting it to the AC posi­
tion. Observe the signal to see that it shifts to its average
voltage level. The shifting of the signal indicates that the
AC-DC switch and the blocking capacitor function properly.
Set the Mode switch to A O N LY and check the A AC-DC
switch for the same waveform shift indication. Place both
AC-DC switches back to the DC position.
(c) Check operation of the VAR. ATTEN. control. When
the control is rotated fully counterclockwise, the vertical de­
flection of the signal should not exceed 1.6 cm. Rotate the
control back to the fully clockwise position.
9. Turret Attenuation Ratios
With the Mode switch at A O N LY, check for 2 cm of
vertical deflection at each position of the A VOLTS/CM
switch by following the information in Table 5-2.
TABLE 5-2
VO LTS/CM Switch
Setting
Calibrator Output
Volts
.05
.1
.1
.2
.25 .5
.5
1
1
2
2.5 5
5 10
10 20
25
50
After checking the A VOLTS/CM turret attenuator, set
the Mode switch to — B O N LY and check the B VOLTS/CM
attenuator in the same manner.
10. Differential Balance
Set the Mode switch to the A-B position and both
VOLTS/CM switches to .05. Set the calibrator switch for
a 100-volt output signal. Set the oscilloscope triggering
controls for a stable display. Ignoring the spikes on the
waveform, adjust the DIFF. BAL. control for minimum square-
wave amplitude.
The maximum allowable amplitude is
0.5 mm. When the control is correctly adjusted and the Z
Unit balances properly, the waveform appears as a straight
line with positive and negative spikes.
An ac mismatch between two tubes or components can
cause the straight line segments of the waveform to tilt
diagonally to form a zigzag pattern. The amplitude of the
tilt at its highest point should not exceed 1 mm. To check
the amplitude, free run the sweep at 20 millisec/cm and
observe the width of the trace. It should not exceed 1.5 mm
(amplitude of tilt and square wave together). After com­
pleting this check, repeat step 5. Then go on to step 11.
11. Characteristic Unbalance
Disconnect the signal from the Z Unit inputs, and set
the Mode switch to the TEST position. Set the oscilloscope
Time/cm switch to .5 millisec/cm. W hile observing the
trace, move the COMPARISON VO LTAG E Polarity switch
to the + , 0, and — positions several times. The overall
baseline shift should not exceed 1 cm. Leave the CO M ­
PARISON V O LTAG E Polarity switch in the 0 position at
the conclusion of this step.
12. Input-Capacitance Standardization
Loosen the set screws in both VOLTS/CM knobs with a
0.05" alien wrench and remove the knobs. This allows ac­
cess to the attenuator adjustments through slots in the front
panel. Each position of the VOLTS/CM control has a
SHUNT and a SERIES adjustment. The only exception is the
.05 position which has only an input-capacitance trimmer
accessible through the SERIES side of the slot.
Connect the 52-ohm cable to the Type 105 Square-Wave
Generator, or equivalent. Connect the other end of the
cable to the 5-to-l '1 ” pad. Connect the other end of the
“ L” pad through the 24-^/xf capacitance standardizer to
the A input connector on the Z Unit. Set the Mode switch
to A O N LY and both VOLTS/CM switches to .05.
To make this adjustment, set the square-wave generator
to produce about 3.5 cm of deflection at a frequency of
1 kc. Set the oscilloscope front-panel controls for “ double
triggering” as follows:
Triggering Mode
Trigger Slope
Trigger Level
Stability
Time/cm
AC Fast
+ Internal
0
Fully clockwise
.5 Millisec
Rotate the Variable Time/cm control slowly counterclock­
wise until you obtain a stable display of overlapping square
waves as shown in Fig. 5-5.
Adjust the input-capacitance trimmer in the A VOLTS/CM
attenuator for best flat top on the displayed waveform
(see Fig. 5-5), disregarding any fast-rise leading edge spikes.
Set the Mode switch to — B O N LY. Disconnect the signal
from the A input connector and connect it to the B input.
Adjust the input-capacitance trimmer in the B VOLTS/CM
attenuator for best flat bottom, disregarding the spikes.
13. Output Voltage Divider Compensation
Increase the square-wave generator frequency to 10 kc.
Set the oscilloscope Time/cm switch to 50 jusec and re­
adjust the Variable Time/cm control to obtain a stable
display of several overlapping waveforms. Adjust the out­
put voltage divider compensations C7655 and C8655 for
®
5-4