1-7. How to Find a Good Earth Ground.
1) A cold-water pipe is a guaranteed earth ground; the cover-plate retaining screw on
most AC outlet boxes is also at earth ground.
2) If the retaining screw is to be used as your earth ground, verify that it is at ground by
measuring the resistance between it and a cold-water pipe with an ohmmeter. The
reading should be zero ohms.
3) If a cold-water pipe is not accessible, connect a 60- to 100-watt trouble- light (not a neon
lamp) between the hot side of the receptacle and the retaining screw. Try both slots, if
necessary, to locate the hot side on the line; the lamp should light at normal brilliance if the
screw is at ground potential (see Figure 3).
Figure 3. Checking for earth ground.
The servicing of these boards requires special precautions. It is strongly recommended to use
Lead Free Solder material in order to guarantee optimal quality of new solder joints.
1-8. Lead Free Information
The circuit boards used in these models have been processed using Lead Free Solder. The
boards are identified by the LF logo located close to the board designation.
Figure 4: LF Logo
Figure 5: LF logo on circuit board
11
SAFETY NOTES
