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e.
By means of the coupling, adjust the posi-
tion of the resistor shaft until an ohm-
meter reading of
£lli
ohms is obtained.
f.
Hold the shaft in this position, and tight-
en the setscrews which secure the cou-
pling to the transformer shaft. Remove the
ohmmeter.
g.
Check and if necessary readjust the level
of the HV output as described in Adjust-
ment of HV Supply Output Voltage, paragraph
4-6.
4-8 SEnlNG THE STOP ON THE HV
CONTROL
This adjustment is to be made only if vari-
able transformer Tl has been replaced. The
movable stop is a small "C
II
clamp which is
attached to the wiper ring on the back of the
variable transformer.
a.
Check that the power cable is dis connect-
ed from the power source.
b.
Use an Allen wrench to loosen the set-
screw which secures the stop to the rim
of the transformer wiper ring, and remove
the stop.
4-7
c.
Attach a DC voltmeter (Model 4l0B, 1,000
volt range) oetween terminal COM on the
control panel an4 socket pin 3 of tube V3.
d.
Plug the Model 7l2B power cable into a
variable transformer set for 115 volts
(measured) •
e.
Turn off the HIGH VOLTAGE switch.
Set the METER RANGE switch at 0-500V
and the HV C ONTR OL to its maximum coun-
terclockwise position.
Turn the AC POWER
switch to ON, and allow at least a 3D-second
warm-up.
f.
Advance the HV CONTROL in a clock-
wise direction until the test voltmeter
reads +380 volts.
g.
Turn off the AC POWER switch, dis con-
nect the Model 7l2B power cable and at-
tach the stop to the transformer wiper ring
so that the movable stop rests against the
stationary stop in such a manner that the HV
CONTROL cannot return in a counterclock-
wise direction.
Note that the stop sets the
minimum voltage applied to the series regu-
lator tubes.
h.
Remove the voltmeter.
i.
Check the setting of variable resistor
R39, as described above.
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