Model 686C Section IV
Paragraphs 4-8 to 4-10
2) Check Magnet Regulator action by dropping line 5) Connect the @ Model 400D or 403A ac voltmeter
voltage to 103 volts. Current should not vary more between the -150 volt bus and ground. The ripple
than 0.025 ampere. voltage must be less than 3 mv over the range of 103
to 127 volts line.
3) Repeat with line voltage at 127 volts.
6) Poor regulation and/or ripple are usually caused
by weak tubes. Check by substituting for V107, V108,
4) Use an isolatedac voltmeter to check ripple voltage.
or V109.
See CAUTION below. Connect voltmeter to upper end
of R31 (white wire) and right hand end of R27 (blue
wire). 4-9. 300 VOLT REGULATED SUPPLY.
This supply uses the -150 volt bus for a reference
The hum or ripple voltage across the magnet must be
voltage. Therefore the -150volt supply must be work-
less than 100 millivolts with the line voltage varied
ing perfectly and be accurately adjusted before the
over the range of 103 to 127 volts.
+300 volt supply is adjusted.
CAUTION 1) Connect the 412A between chassis and +300 volts
at red wire, V106 Pin 1. (See figure 4-5).
The magnet power supply uses a voltage-
doubler circuit directly connectedto the power
2) Adjust the voltage to exactly +300 volts with R141.
line. When the power cord is inserted in a
polarized three-wire outlet that is properly
3) Check the regulation by slowly varying the line
wired, approximately 150 volts dc and 6.3
voltage down to 103 volts and up to 127 volts. There
volts ac appear between electrical ground and
should be no visible change on the 412A voltmeter.
the end of R31 to which the white wires are
connected. If the line cord is reversed, ap-
4) Check the ripple voltage with the 400D or 403A
proximately 122 volts ac as well as the 150
voltmeter. The ripple should read less than 10 mv
volts dc will be present on the white lead which
over a line voltage range of 103 to 127 volts.
may give false ripple voltage measurements.
Check cord polarity by measuring the voltage
5) Recheck -150 volt supply and reset if necessary,
between the white-wire end of R31 and ground.
then reset +300 volt supply.
Use a multimeter type ac voltmeter with a dc
blocking capacitor in one lead; you should
measure 6.3 volts ac and not 120 volts ac.
4-10. HELIX SUPPLY.
When checking the ripple voltage, the volt- 1) Check the Helix Regulator by measuring the volt-
meter case must be isolated from ground. age from VlOl pin 1 to ground. Use the 410B dc vtvm
Temporarily disconnect the voltmeter NEMA with 1OO:l multiplier probe. The voltage will vary
ground connector by using a two-prong adapter from +400 volts when the FREQUENCY dial is at the
with the pigtail floating. Do not touch the low frequency end to +2,000 volts when the FRE-
voltmeter cabinet while making. this check. QUENCY dial is at the high end.
2) Adjust the FREQUENCY dial until the voltage is
Poor regulation and excessive ripple are almost always
1, 000 volts. Slowly vary the line voltage from 103 to
due to weak tubes (V1 to V5) or noisy neon lamps (V6
127 volts. There should be no visible change on the
through V11). First replace tubes, then try replacing
voltmeter.
the neon lamps. In the case where a neon lamp is
noisy a good method for determining which lamp is at
3) Reduce linevoltage to 103 volts. Set Helix to 2,000
fault is to shunt a 470,000 ohm, 1/2 watt resistor
volts (FREQUENCY dial at high end). Measurevoltage
across each lamp while watching for ripple indication
on collector (pin 7 of V102). The voltage must be
on the 400D. If ripple decreases with the addition of
greater than 2,050 volts. If not, replace V102.
the 470,000 shunt resistor, change that particular
neon lamp.
4) Raise line voltage to 127 volts. Set Helix voltage
to 400 volts (FREQUENCY dial at low end). Measure
voltage on collector (pin 7 of V102). The voltage must
4-8. -150 VOLT REGULATED SUPPLY.
be less than 2,600 volts.
1) Connect the 412A voltmeter from chassis to -150
volts at R129 (150K white wire). (See figure 4-5.) 5) TURN THE SWEEP OSCILLATOR POWER OFF.
Adjust power line voltage to 115 volts. Disconnect the bwo tube high voltage connector. Con-
nect four 100,000 ohm, 1 watt resistors in series and
2) Adjust R148 for exactly -150 volts dc. connect them from the bwo tube side of overload re-
lay K103 to ground. Rotate the FREQUENCY dial to
3) Drop linevoltage to 103 volts and watch for change the low end. Rotate the CATHODE CURRENT control
in -150 volt level. There should be no visible change. full counterclockwise.
4) Raise line voltage to 127 volts and watch for a 6) Turn on the equipment and measure the voltage
change. None should be noticeable on the @ Model across the four lOOK resistors. With 400 volts, 1 ma
412A. will flow through them.
00034-1 4-7 |
ACEC
