Tektronix Type Z Instruction Manual page 25

JUNCT ON OF
R7653 AND R7652
COLLECTOR
P NS 1 AND 3,
NTERCONNECT NG
PLUG
Fig. 5-3. Location of jumper test points used for making steps 2, 3,
and 4 push-pull balance checks.
2. Output Cathode Follower Balance
Remove the plug-in cable extension and insert the Z Unit
directly into the oscilloscope plug-in compartment. Tighten
the securing rod to hold the unit fully plugged in.
(a) Connect a short jumper between pins 1 and 3 at the
interconnecting plug (see Fig. 5-3 for location). The posi ­
tion of the free-running trace on the crt is the "vertical ­
system electrical center". Note the position of the trace for
future reference in the procedure. Remove the jumper.
(b) Connect the VOM between the wiper arms of the
PO ITION control (R7653) and adjust the control for a zero
reading on the meter. Connections can be made at the
junction of R 7 653 and R7652 and the junction of R7653
and R8652 (see Fig. 5-3). Disconnect the VOM.
Use care when connecting jumper leads in the
following steps.
quickly damage transistors. Also, if parasitics are
produced when a jumper is connected, they can
be suppressed with a ferrite toroid.
jumper lead through the toroid two or three times.
(c) Connect a jumper between the collectors of Q7644
and Q8644 (see Fig. 5-3). Rotate the OUTPUT CF BAL ad ­
justment (R7658) to bring the trace back to the "vertical ­
system electrical center" position established in step 2 (a).
Remove the jumper.
Fig. 5-4 shows all internal adjustments not accessible from
the front of the unit.
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BASE OF P N 1,
COLLECTOR P N 1,
OF Q8644 V8634
CAUTION
An incorrect connection
Wind the
3. Output Amplifier Balance
Connect the jumper between the bases of Q7644 and
Q8644 (Fig. 5-3). With balanced transistors the trace will
not shift more than 1 cm from the "vertical-system electrical
center" position. Disconnect the jumper.
4. Differential Amplifier Tube Balance Test
Connect the jumper between pins 1 of V7634 and V8634
(Fig. 5-3). The trace should not shift more than 3 cm from
"vertical-system electrical center". Disconnect the jumper.
5. Variable Attenuator Balance
Position the trace onto the screen using the PO ITION,
AMP DC BAL, and VAR. ATTEN. BALANCE controls.
the VAR. ATTEN. BALANCE control so the trace no longer
shifts as the VAR. ATTEN. control is rotated. During ad ­
justment of the VAR. ATTEN. BALANCE control, it may
be necessary to reposition the trace to keep it centered
on the crt by using the PO ITION and AMP DC BAL con­
trols.
6. Amplifier DC Balance
et the PO ITION control to midrange and adjust the
AMP DC BAL control to position the trace directly behind
the center horizontal graticule line.
7. Gain
et the Mode switch to A Only. Apply a 0.2-volt square ­
wave signal from the oscilloscope calibrator to both input
can
OUTPUT
CF BAL
Fig. 5-4. Location of internal adjustments accessible from left side
of Z Unit. Turret attenuator compensation adjustments are acces ­
sible through front panel after outer VOLTS/CM knobs are re ­
moved.
Calibration — Type Z
et
TURRET
ATTENUATOR
5-3