5238 HYDROGRAPHIC MANUAL PaGE 472 



b. Clfani'ng.—BeioTe each day's operation, the inside of the recorder cabinet 

 should be wiped clean with a dry rag, and the metal recorder platen rubbed to a polish. 



Every 3 weeks the governor and keying contacts should be inspected and cleaned. 

 The contact surface should be filed flat, and if there is evidence of bad pitting, the gov- 

 ernor should be renewed. 



Every 2 months the driving motor and dynamotor brushes and comnmtator should 

 be inspected for wear. The commutator should be smoothed with a fine grade of sand- 

 paper (emery must not be used), and the brushes renewed if necessary. After new 

 brushes have been installed, the instrument must be run for 2 hours to wear them in 



properly. 



5238. Operating Difficulties 



An 808 Fathometer operating so as to give inaccurate or unsatisfactory results, 

 generally, but not always, gives evidence of this on the fathogram. But it should be 

 noted that a number of unrelated difficulties manifest themselves in the same way. A 

 lack of soundings, inaccurate soundings, or unsatisfactory results may be caused by one 

 of the following: 



(a) A poor connection or shorting of the cables from the fish, or battery, evidenced by no sound- 

 ing or continuous marks across the fathogram. 



(6) Improper pressure of the stylus on the paper, evidenced by no record, torn paper, or a succes- 

 sion of hiatuses of short intervals in the record. 



(c) Dirt or carbon on the metal platen under the paper, evidenced by horizontal marks throughout 

 the fathogram. 



(d) Improper echo-amplifier operation, evidenced by the transmitted signal or the echo, or both, 

 being recorded weakly, or not at all; or by a continuous black mark across the fathogram. 



(e) Improper operation of the contactor mechanism, evidenced by a jagged record of the trans- 

 mitted signal and echo, a sudden equal change in the recorded position of both, or the entire absence 

 of signals. 



(/) Defective parts or connections, evidenced by irregular record, lack of record, or continuous 

 marks across the fathogram. 



ig) Play in the phasing head, evidenced by a sudden change in the recorded position of the 

 transmitted signal and echo. This should be tested by attempting to move the head by hand. Such 

 a fault can be temporarily remedied by inserting three paper shims between the phasing head and its 

 holding ring, placing the shims about an equal distance apart. The head must not be made so tight 

 as to prevent index adjustment. 



(h) Continued marking of the stylus after depression of the fix-marker button. This is ordinarily 

 not caused by the button sticking, but by oscillation of the amplifier after the button has been re- 

 leased. The remedy is to turn the gain control down momentarily in order to stop the oscillation. 



In addition to the difficulties that are evidenced on the fathogram, there are a 

 number of operational troubles which may occur and most of which have occurred on 

 one or more of the instruments in use. Some of these difficulties are still being analyzed 

 and it is expected that the redesign of certain parts may eliminate them. 



(i) Trouble with the governor or keying contacts— the contacts should be filed occasionally to 

 a uniform surface and the keying contacts or the entire governor renewed if the trouble is not eliminated 

 by filing. 



if) Improper operation of the reed tachometer resulting in loss of necessary definition. This may 

 be caused by excessive vibration of the cabinet by external forces. The recorder cabinet should be 

 supported on Lord mounts, type 200-XPH-GO, or some shock-absorbing material, such as rubber. ' 



(k) Lack of amplifier gain or unsteady operation may be caused by defective type 1851 or 1853 

 vacuum tubes. These types of tubes have occasionally functioned erratically; they should be tested 

 for emission and be subjected to a mechanical shock by being rapped sharply during the emission tests. 



(l) Damage to gears by reason of imperfect design or alinement. The driving motor has l)een 

 known to become loose on its mounting, which might account for the improper meshing of the gears. 



