Monroe Electronics Electrostatic Voltmeter - Isoprobe® - model 279L - Manual (Page 13)

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SECTION 6
ADJUSTMENT
A. General:
The following procedure sequence is such that it will aid in troubleshooting the unit. The circuit board layout is
illustrated in 3570/22. All test points and reference numbers used in this section are indicated on schematic 279L/1,
assembly drawing 3570/22 and are identified in Table 6-2 at the end of this section.
The procedure should be followed in the order given to prevent possible interaction of controls.
A phase-compensated (normal) Monroe Electronics, Inc. Model 1034E or 1034S miniature probe must be used
wherever the use of a probe is indicated.
B. Recommended Equipment:
Oscilloscope – 50kHz bandwidth, 0.1mV/div sensitivity
Compensated high voltage probe for oscilloscope (optional)
High voltage source – 500V, Stanford Research Systems Model PS350 or equivalent
Digital voltmeter – five-digit, 0.1mV resolution
High voltage probe – 1000:1, 0.01% (for DVM)
Shorting plug, ME P/N 9232301, Keystone P/N 1463 (used at JP8)
C. Initial Setup and Adjustments:
1. Insure that available nominal power line voltage and frequency match those shown of the back panel of the
unit and that the line voltage selector is properly configured. (See Section 2, INSTALLATION). Do not
apply power at this time.
2. Remove cover from unit.
3. Consult Table 6-2. Make the following potentiometer adjustments: Set R53, R54, R108 and R111 to
midrange. Set R55 and R56 counterclockwise. Set R107 clockwise.
4. Connect a probe to the rear panel connector and fixture it to look at a metal test plate at least six inches
(150mm) square at a distance of 0.005 inch (0,13mm).
5. Connect a high voltage source to the test plate and set its output for zero volts.
6. Install a shorting plug at JP8 and disconnect P300. Jumpers JP1, JP3, JP4, JP6, and JP7 should be
installed.
7. On the front panel, put the OPER/STBY switch in STBY and turn on the display.
8. Connect the 279 to the appropriate source of power and turn on the rear panel power switch.
D. Low Voltage Power Supply Check:
Check the following test points with a digital voltmeter between the test point and chassis.
Test Point D.V.M. Reading
TP15 -15 VDC 0.5 V
TP16 +15 VDC 0.5 V
TP18 +15 VDC 0.5 V
TP20 -15 VDC 0.5 V
Table 6-1