Section V Model 140A
Paragraphs 5-21 to 5-27
Table 5-3. Condensed Adjustment Procedure
External Equip-
Test Procedure Adjust
ment Required
1. Low DC Voltmeter Measure:
Voltage -1OOv (Violet) R200B
Supplies -12.6~ (White/Violet) R200C
+1OOv (White/Red) R200A
2. High DC VTVM; 1OO:l a. Calibrate Divider - Voltmeter R319 for -2350 volts
Voltage Divider; Voltmetei combination.
Supply Calibrator
b. Measure -2350v
3. Intensity None a. Center a defocused spot. R312 until spot is just
Limit extinguished.
b. Set INTENSITY to 10 o?clock.
4. Astigmat- None Center a low-intensity FOCUS and ASTIGMATISM
ism spot. for sharp spot.
5. Geometry Audio Oscillator a. TRIGGER LEVEL:. . . . AUTO R343 for straightest
SWEEP TIME: . . 0.2 MSEC/CM edges.
b. Connect 400 kc sine wave to
vertical INPUT.
c. Obtain pattern 8 cm high.
I
I
6. Cali- a. SENSITIVITY: . . . . 0.5V/CM Cal Adj. R205 for 10 cm
brator deflection.
b. Apply 1Ov p-p from Voltmeter
Calibrator to vertical INPUT.
c. Adjust vertical VERNIER for
10 cm deflection.
d. Connect 1OV CALIBRATOR to
vertical INPUT.
pulling the transistor from its socket. All other 5-23. FUSES. If the -100, +loo, or +250 volt supply
low voltage power supply transistors are located on should be accidentally shorted to ground, the fuse
the low-voltage circuit board. for that particular supply will blow. This cuts off
current in the supply and protects the transistors.
5-21. Nominal voltages at significant points in the
5-24. The -12.6 volt supply is not fused, but employs
supply are given in the low-voltage power supply
a surge protector, Q184, for protection against brief
schematic. Plug-ins must be installed when checking
shortings of the output to ground. The supply should
these voltages. Correct voltages for points not
immediately function normally upon removal of the
marked for voltage are generally obvious by being
short.
connected (directly or indirectly) to a supply output.
Transistor base voltage in most cases should not
5-25. LOSS OF REGULATION. If loss of regulation
measurably differ from emitter voltages when meas-
occurs in a supply, refer to Table 5-4. Thepro-
ured with respect to ground. Voltage drops across
cedure outlined in this table may not always pin down
breakdown diodes are indicated on the schematic.
the exact trouble, especially if a component other
than a transistor or breakdown diode has failed, but
5-22. EXCESSIVE RIPPLE. The cause of excessive it will usually indicate the general location of the
120-cycle ripple on any of the supplies can be isolated failure. In using the procedure, follow the steps
to input filter or regulator circuits by comparing listed under a particular symptom in the given order.
ripple voltages at the rectifier outputs withthe values In some cases, more than one fault may exist.
given on the schematic. If ripple at these points is
excessive, check capacitors C121, C122, C141, C161,
or C181. If ripple is high and is 60 cps, one of the
5-26. HIGH-VOLTAGE SUPPLY.
rectifiers is probably open. If normal, the cause
is most likely low gain in the amplifier transistors. 5-27. If one high-voltage supply output is zero but
In the -100 volt supply, slave amplifiers Ql6l other outputs are normal, look for the unlit filament
and/or Q163 could be open, and the only indication of a bad rectifier (V302 thru V305). Normal DC
might be poor regulation and ripple at low line voltage. voltages are given on the high voltage schematic.
5-4 01638-1 |