Tektronix TYPE Z PLIG-IN Instruction Manual page 23

stated previously. Where necessary, use matched and se­
lected parts obtained from the factory.
5. Waveform Distortion
If waveform distortion occurs, first check to see which
ranges of the VOLTS/CM switch have distortion.
distortion only occurs on one or two ranges, check the
compensation of the input turret attenuators.
tortion occurs on all ranges, first check the compensation
of the probe used. Use a calibrated, 30-mc-bandwidth,
test oscilloscope for signal tracing through the unit.
test oscilloscope aids in determining which stage (or stages)
is introducing the distortion.
frequency distortion, consider the loading effect of the
probe. When the defective stage has been determined,
check tubes and transistors (by substitution).
the settings of frequency compensation components such as
L7632, L8632, L7645, L8645, C7655, and C8655. If none of
these checks determines the cause of the trouble, use volt­
age and resistance checks on the defective stage.
6. Incorrect Comparison Voltages
This trouble can be detected only with a high precision,
infinite-impedance voltmeter such as described in the C a l­
ibration section under Equipment Required. To check these
voltages, connect the voltmeter from test point C to ground,
set the Helidial at 10.000 and set the Range switch at
100 V. The voltage measured should be 100 (± 0.15)
volts in both the + and — positions of the Polarity switch.
If both the + and — voltages are correct, check for 10
(± 0.02) volts with the Range switch set at 10 V and 1
(±0.005) volt with the Range switch set at 1 V. If either
the 10 V or 1 V ranges are incorrect, check the Range
switch contacts and rotors, the precision attenuators, and
the setting of R7689 (CAL. 5 adjustment).
If voltages obtained on both the + and — 100 V ranges
are incorrect, check the settings of the CAL. 1, CAL. 2,
CAL. 3, and CAL. 4 adjustments.
incorrect, check the settings of CAL. 1 or CAL. 2 as applica­
ble, and the voltages on Q7674 or Q8674.
If the
If the dis­
The
In signal tracing for high-
Then check
If only one polarity is
Poor regulation of the comparison voltage may be caused
by defects in any of the following: D8679, Q8672, Q8674,
D7675, Q7672, Q7674, D7686, D7687, D7688, or V7689.
7. Short Circuit
If the oscilloscope must be turned off because
Z Unit is the cause of resistors overheating in the oscillo­
scope power supply, and possibly in the unit as well, re­
move the unit from the plug-in compartment.
COMPARISON VO LTAG E switch in the + Position. Make
the following resistance-to-ground
interconnecting plug. The measurements listed in Table 4-1
are typical values obtained using a 20,000 Q/V VOM.
When the trouble is corrected, replace the overheated
resistors in the oscilloscope and check the Z Unit for any
other troubles under operating conditions. It may be desir­
able to perform steps 1 through 11 in the Calibration section
of the manual. These steps provide a systematic approach
to important voltage measurements, balancing each stage,
and making operational checks.
TABLE 4-1
INTERCON N ECTIN G
CIRCUIT SOCKET
PIN NUMBER
Output 1 & 3
Ground 2
No Connection 4, 5, 6, 7, 8, and 16
- 1 5 0 V 9
+ 100 V 10
+225 V 11
+350 V 12
6DJ8 Filament 13 and 14
Transformer Primary
Series Filament String 15
*W ith CO M PARISO N V O LTA G E Polarity switch at — position.
Maintenance — Type Z
the
Place the
checks at the 16-pin
RESISTANCE
TO GROUND
9.8 k
0
Infinite
10.7 k
*17.0 k
8.7 k
*7.7 k
19.0 k
*14.0 k
60 to 80 k
Infinite
72 a
4-5