TROUBLE SHOOTING PROCEDURE SYMPTOM PROBABLE CAUSE ALL UNITS: No.  530, 550 and 540 remote 3.  Depth reading a.   Fish present in abruptly changes to a transducer beam 1.      Unit   does   not   turn on: no logo  (See  Sect. 1) 2.      No   depth   reading, even at maximum sensitivity,   and   on   the 550, "No Echo" is displayed (See Sect.  3) a.   Check  fuse  or  circuit breaker  in  the  power supply circuit: b.   Check power connection for correct  voltage  (12V- DC) and polarity (negative ground); c.   Make sure power connectors  are  clean and free from corrosion. a.   Depth    deeper    than maximum     capability of the unit; b.   Extremely poor reflection   coefficient: i.e., Very muddy, silty bottom condition; c.   Very densely aerated region, or heavy subsurface interference preventing echo penetration; d.   Check transducer connection: e.   Check transducer mounting   and   clean face. f. Defective   transducer or wiring. much shallower reading,   then,   seconds later,   returns   to   normal (See Sect. 3) 4. Depth reading abruptly   changes   to   a much    deeper    reading, then, seconds later, returns  To  normal  (See Sect.  3) 5.        Random    "beeps" from audible alarm when the DEEP ALARM is on.  (See Sect.  9) 6.        Random    "beeps" from audible alarm when SHALLOW ALARM    is    on.        (See Sect.  3) pattern; b.   Extreme    subsurface interference; c.   Readjust sensitivity to a lower level a.   Boat   motion   causes momentary     loss     of transducer/water contact, so depthfinder responds to    second    or    third multiple echo. b.   Readjust sensitivity to a higher level. a.   This   is   an    audible, no-echo alarm; increase the sensitivity; b.   Momentary     loss     of transducer/water contact,  (due  to  high speed,    rough    seas. etc.)   creating   a   "No Echo" condition. a.   Fish present in transducer beam pattern; b.   Extreme    subsurface interference; c.   Readjust sensitivity to a lower level. 21