Tektronix 1A4 Instruction Manual page 134

Calibration—Type 1A4
removed for this illustration)
Fig. 7-12. Location of step 7 test points and OUTPUT DC LEVEL
adjustment.
NOTE
Do not connect the voltmeter to the +100 V avail-
able at pin 10 of the interconnecting plug. This
voltage is electrically located at the output side of
a decoupling network and will therefore be a few
volts less than the non-decoupled +100 V avail-
able at the output of the oscilloscope power sup-
ply circuit. The non-decoupled +100V in the
oscilloscope can be easily located by the color
coded wire (brown-black-brown on white) and by
referring to Fig. 7-12A.
e. Calculate 67.5% of the measured +100 V supply.
f. Using the small screwdriver, momentarily short pins
1 and 3 of the interconnecting plug. This can be conveniently
accomplished by shorting pins AH and Al together on the
Output board (see Fig. 7-12B). Note the position of the trace
'on the oscilloscope CRT. This is the DC electrical center for
the oscilloscope vertical amplifier.
Do not short any of these pins to ground.
g. Using the Channel 1 POSITION control, position the
trace to the same location that was noted in step 7f.
h. Connect the precision DC voltmeter between ground
and either pin AH or Al (about 67.5 V) on the Output board
i. CHECK—Meter reading should be 67.5% of the non-
decoupled +100-V supply as calculated in step Ze. Accu-
racy: Within 2% of the step Ze calculated voltage.
j. ADJUST—OUTPUT DC LEVEL control R360 (see Fig.
7-128) for a meter reading of exactly 67.5% of the measured
+100-V supply. (R360 should be adjusted to obtain the same
voltage as calculated in step 7e).
k. Disconnect the voltmeter test leads.
1. Place the oscilloscope in the upright position.
m. Disconnect the flexible extension cable and insert the
Type 1A4 directly into the oscilloscope plug-in compartment.
(The Type 547 Oscilloscope does not have to be turned off
when making this change.)
NOTES