POWER DESIGNS 3K10 Manual page 10

3K10
SECTION 4
IMINTENANCE
4-1. GENERAL
All maintenance and adjustments should be made with the power
supply set for negative output. Most of the low-level regulation
circuits are tied electrically to the positive output bus. Setting
the supply for negative output brings most of these circuits close
to groxmd potential.
4-2. CALlBRilTlON
To check or reset the calibration of the unit, the power supply
should be set for negative output and the voltage selector switches
set for 2900 volts out, with the vernier control at its minimum setting.
The output of the supply should be connected, through an appropri
ate voltage divider, to the input of a differential or digital voltmeter
of accuracy 0,1 fo or better. Allow the supply to warm up for 10 minutes
or more, then adjust potentiometer R37, if necessary, until the output
voltage, as measured on the external meter, agrees with the selector
switch settings to within 0.25^.
The same measuring setup, may be used to check the calibration of
the unit at other output voltages and the tracking of the vernier control.
4-3. LO/O) REGULATION
To adjust load regulation, set the power supply for negative
polarity and 500 volts output. Monitor the output voltage by means
of a differential voltmeter. Adjust trimmer potentiometer R63, if
necessary, until the change in output voltage upon application or removal
of a. 10 milliampere load is less than O.OOI^ or 3 millivolts (load regu
lation can generally be set considerably closer than this). Load
regulation should also be checked at 3 KV output, but will usually be
well within specifications at this voltage level if it has been cor
rectly set at 500 volts.
CAUTION: THE lV-101 BLOCK, THE TRANSISTORS ON THE HEAT SINK AND THE
PRIMARY OF T2 AND THE SECONDARY OF T3 ARE OPERATED DIRECTLY
'FROM THE LINE, WITHOUT AN ISOLATION TRANSFORIffiR.WHEN SER
VICING OR TROUBLESHOOTING THIS SECTION OF THE CIRCUIT, THE
POWER SUPPLY SHOULD BE OPERATED FROM A 1;1 ISOLATION TRANS-
FORT,lER FOR PERSONNEL SAFETY AND TO PREVENT DAMAGE TO THE
IPOmR SUPPLY.
DANGEROUS POTENTIALS T.5AY EXIST INSIDE THIS POWER SUPPLY.
CAPACITORS MAY HOLD THEIR CHARGE FOR SOTIE TIME AFTER THE
UNIT HAS BEEN TURNED OFF. TAKE ALL PRECAUTIONS NORMALLY
USED IN WORKING ON HIGH VOLTAGE EQUIPMENT WHEN SERVICING
THIS SUPPLY, IN THE POSITIVE OUTPUT POLARITY POSITION
CONTROL CIRCUITS AND SEMICONDUCTORS ARE OPERATING AT
HIGH VOLTAGE AND DANGEROUS POTENTIALS MAY EXIST ON THE SEMI- /
CONDUCTOR CIRCUITRY. /
901 4_1