International projectionist (Oct 1931-Sept 1933)

November 1931 INTERNATIONAL PROJECTIONIST 15 sofar as many members objected to the 5 cents charge made for this purpose), since there was a balance of more than $10,000 in the Journal Fund on this date/" But Secretary-Treasurer Lemaster, at the 1919 Convention, had spoken of the lack of cooperation being received from local unions and from individual members in furnishing news items and their correct addresses for delivery of the Journal." This may have a motivating factor in the suspension. The "General Bulletin" For three and one-half years the Generl Bulletin was issued weekly. On January 1, 1924, it was made semimonthly." President William F. Canavan explained this change was due to the heavy financial burden of weekly publication and also because "the news was not of direct nature." This, he added, was contrary to the purpose of publication.''' Semi-monthly publication was con tinued until May 6, 1925, when the International officers decided to issue the General Bulletin but once a month. The announcement of this change stated that "inasmuch as the majority of the local unions hold their meetings once a month, it is believed this policy will best serve the interests of all concerned'"*. It was also intimated that the money saved on the printing of the extra issue each month could be used elsewhere to good advantage. The General Bulletin continues today as a monthly publication. REFERENCES: [Note: The following references, but one, refer to the Combined Convention Proceedings.— Ed.'\ 'Page 18 (1895 Convention); ^ page 23 (1895 Convention); "pages 43, 45—47 (1897); * page 62 (1898); 'page 253 (1907). "Page 266 (1908); 'page 316 (1909); « page 375 (1910); "page 356 (1915); and pages 599 and 609 (1917). '"Page 747 (1922); "page 680 (1919); 785 and 805 (1924); "pages 785 and 805 (1924); "General Bulletin No. 191, April 21, 1925. Recurrent Reproducer Noise THE sources of noise of an intermittent or recurrent nature are usually much more difficult to locate than are the causes of steady noises. The very fact that such noises come and go intermittently makes it difficult to know when the cause has been located. Preventive measures are therefore much more effective in dealing with such noises than are remedial measures. The causes of intermittent noises are briefly: Batteries — run down, loose connections ; fuses — corroded, dirty clip contacts; charging panels — loose connections; amplifiers — loose connections; poor tube contacts; faders — dirty contacts; motor generators — brushes, commutators; motor generator filters — loose connections. Noisy "B" Batteries As B-batteries (dry type), deteriorate, they tend to become noisy and should, therefore, be replaced when the voltage drops below the proper figure. This is especially true of the "C," or grid, batteries, which are used in some of the earlier type amplifiers. Spring terminals on these batteries should be kept clean and care taken to make certain that firm contact is maintained with the spring terminals inside the battery boxes. Charging Batteries The tops of storage batteries must be kept clean and dry. They should occasionally be wiped off with a cloth moistened with either a solution of bicarbonate of soda or ammonia. The connections should be kept tight and prop erly protected from acid fumes by the use of non-oxide grease. It is well to remember that immediately after batteries have been charged, gases will still be forming in the electrolyte. These cause slight variations in the internal resistance of the battery, resulting in noise being introduced through the amplifiers. Batteries should therefore be taken off charge at least 30 minutes before the sound system is needed. Fuses sometimes become corroded internally, and frequently dirt collects or corrosion occurs at the ends where they fit into the clips. Either of these conditions may result in noise. This is especially true of the battery fuses in the 90-volt photo electric cell and film amplifier circuits. Connections and knife-switch contacts should be checked occasionally to reduce the possibility of noise from loose connections and poor contacts. At the time of installation, all connections are made secure. Subsequently, however, vibration may cause these connections to work loose, with the resulting possibility of noise. The switch-blade contacts on the battery charging panel should be kept clean and bright by occasional cleaning with fine sandpaper. Vacuum Tubes Amplifiers, especially the first stages following the photo electric cell or disc pick-up, are very sensitive, and inspection of them at periodic intervals of, say, one month, is good insurance. Vacuum tubes should be removed in order to clean the contacts on the ends of the prongs and the spring contacts of the tube sockets. The eraser on an ordinary lead pencil is excellent for this purpose, but care is necessary to insure that none of the rubber particles remain on the contacts after cleaning. A file or sandpaper must not be used. The spring pressure should be noted when the tube is replaced. Appreciable pressure is necessary to insure good contact, and if this pressure is lacking, the contact springs of the socket should be bent up to increase the pressure. All power should be turned off while work of this nature is done, in order to prevent shocks or damage to the equipment. Grid leak contacts should be cleaned, and spring contacts should hold the grid leak firmly in place to prevent noise due to poor contacts. P. E. C. Amplifiers The photo electric cell amplifier is suspended in a crade by coiled springs so that it is free to swing without touching the metal amplifier housing. An occasional inspection is advisable to make sure the amplifier is swinging freely and the springs have not become stretched. It is essential that the anode block associated with the photo electric cell be securely fastened down and that the anode lead from the cell has sufficient slack to prevent the transmission of vibration. The amplifier wiring should be inspected for signs of loose connections. If they exist, loose connections are quite likely to result in intermittent noises, the causes of which may prove to be exceptionally puzzling. Rheostats, potentiometers and keys should have their contacts cleaned occasionally. The time so spent will "be well worth while in preventing noise from these sources. Fader Contacts Fader contacts will give little trouble if they are cleaned occasionally with chemically pure carbon tetrachloride. Ordinary carbon tetrachloride should not be used for this purpose. After cleaning the contacts with tetrachloride, a thin coating of vaseline should be applied and the excess wiped off. If a motor generator set is used for filament or plate voltage supply, it is advisable to make weekly check inspections of the condition of the brushes and commutator. If it is equipped with a filter, the connecting straps should be checked to make sure they are tight. Particles of dust or dirt may occasionally lodge in the light gate and cause noise if they move due to the machine vibration. Ordinary care in routine cleaning will prevent trouble from this