Section 4
MAINTENANCE
GENERAL:
Field maintenance of Model 268A should be limited to cleaning of the insulating standoffs,
cleaning of the case and occasional field-meter zero adjustment.
Further repairs and adjustment require special equipment and are beyond the scope of this
manual.
Factory service is advised.
CLEANING, INSULATORS:
The insulating standoffs (supporting the measuring plate) are specifically designed to
minimize the effects due to contamination of their outer surfaces. Leakage paths created by
the skin oils in fingerprints, tobacco smoke, dust, etc. will eventually degrade their
performance such that the self-decay rate of the plate will exceed 10% over a five-minute
period, indicating the need for cleaning.
IMPORTANT!
DO NOT USE SOAP, DETERGENT OR TAP WATER
TO CLEAN THESE INSULATORS
Clean the exposed surfaces of the insulators with mixture of 70% clean technical grade
isopropyl alcohol and 30% distilled water, using a soft toothbrush. The unit should be
inverted while doing this to minimize the amount of liquid entering the case.
The insulators should then be allowed to air-dry.
CLEANING, CASE:
General cleaning of the case for aesthetic reasons is best done with a clean lint- free cloth or
wiping pad dampened in the alcohol/water solution noted above.
FIELDMETER ZERO:
Airborne contaminants entering the sensitive aperture of the fieldmeter probe may cause a
zero shift, which will affect the accuracy of measurement.
A multi-turn potentiometer is provided on the upper section of the instrument to adjust
fieldmeter zero. Adjust for an indication of zero volts on the 2000 volt meter range with the
ZERO button pressed in.
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