Interference Sources - Humminbird CH Thirty II Operation Manual

CHANGING A STYLUS
After prolonged running a stylus may tend
to wear and require replacing. To replace
the stylus element, open the front cover
and rotate the stylus belt until the stylus
holder is in the center of the unit.
Your new stylus will come in two pieces.
There is a right hand element and a left
hand element. The right hand element
makes contact with the pick up bar to the
right of the stylus belt. The left hand
element makes contact with the paper
and does the printing (burning).
Follow steps A through D in figure 6 for
both elements.
A new stylus will on occasion have a
sharp tip which scratches the paper. A
small piece of fine abrasive paper should
be placed flat against the chart paper and
held there for 5 to 10 seconds while the
chart is running, so that the writing point
of the stylus is smoothed off.
Note: Periodically clean the bass stylus
bar on the right of the belt, occasionally
sanding lightly to prevent the stylus from
grooving the bar.

INTERFERENCE SOURCES

The chart recorder contains noise suppression circuits to make its performance as immune to
external noise sources as possible.
There are two groups of noise sources which may degrade performance in certain conditions.
These are electrical sources and mechanical sources.
Mechanical sources include such things as improper mounting of the transducer, causing water
turbulence at high speeds, appearing as degraded performance.
Also at high speeds some propellers cavitate and produce vibration noise which will excite the
transducer and produce low level signals. Electrical sources include such obvious things as
ignition noise from engines. On some engines external gap spark plugs are used which are
partially troublesome. Electrical motors and generators can produce brush noise, and other