Exhibitors Herald World (Oct-Dec 1930)

December EXHIBITORS HERALD -WORLD THE BLUEBOOK SCHOOL By F. H. RICHARDSON BLUEBOOK SCHOOL QUESTION NO. 65. — (A) What solutions are recommended for cleaning battery tops? (B) What precaution is necessary when using such solutions? (C) Just what would you do if you accidentally spilled some electrolyte on the battery top? (D) Explain in detail just what attention you would give your battery top. ANSWER TO BLUEBOOK SCHOOL QUESTION NO. 46 The question was : A constant voltage is applied to the photoelectric cell. Upon what does the amount of current flow from it to the amplifiers depend? Wliat is the strength of the impulses sent out by the p. e. cell? THOSE who answered correctly within the meaning of the question as it was intended to apply, formed a good-sized group. Brothers Dudiak and G. L. Doe were the only two who dealt with other phases of the matter. Those answering correctly were Frank Dudiak, G. L. Doe, Carl Daugherty, Gayle Grubaugh, G. T. Baldy, T. R. Roand, Robert Dodson, L. Brennan, L. D. Felt, Bill Doe, F. T. Spencer, Smart Kliene, W. T. Lathrop, R. B. Fanning, William Truax, Frank Dual, Matt Golding, Thomas T. Mitchel, J. R. Malley, Ben Edwards, Tom Van Vaulkenburg, L. G. Sands, Harry Crowley, Brandell Lomax, J. G. Kaufmann, H. G. Stapleton, "Another Doe," W. R. Morehouse, Tom Allding, Peter Itt, T. D. Sands and F. H. Emmerson. I will publish two answers. G. T. Baldy says: "When the exciting lamp has been lighted, thus illuminating the interior of the photoelectric cell, negative charged particles of electricity, called electrons, are thrown off, or emitted, by the light-sensitive material by reason of the action of the light thereon, and in exact proportion to the amount of light. "These electrons ionize the gas contained within the cell, in which condition the gas becomes a conductor of electricity in exact proportion to the amount of its ionization. The amount of light is of course in proportion to the density of the sound track at any instant of time, hence the conductivity of the gas is altered exactly in proportion to the sound track density from one instant to the next. Therefore the current flow is controlled by this action. "As to the strength of the impulses sent out by a photoelectric cell, they are very weak — so much so, in fact, that they must be amplified approximately 100,000,000 times before they are available for use at the horns." (That is not just as Brother Baldy answered, but in rewriting his answer, I have not in any degree changed his meaning.) Friend Dudiak says: "In the Western Electric system, the constant voltage applied to the p. e. cell is 90 volts. In the R C A system it is 200. The amount of current flowing out of the p. e. cell depends upon several factors, among them : "(a) Strong or weak cell (in a strong cell, greater ionization will take place, hence greater quantity of current will flow). "(b) Amount of light entering from the exciting lamp. "(c) Correct adjustment of slit. "(d) All parts being free from dirt. "(e) Good electrical contacts and connections. "The strength of the impulses sent out by the p. e. cell depends on the difference of density between the white and black lines (Movietone) ; the greater the difference, the greater the current. More generally, this current is so weak that it must be amplified 100,000,000 times before it can be utilized to operate a loud speaker acceptably. This is why this part of the equipment must be given careful attention, as it will easily pick up extraneous current leaks and amplify them along with the sound current." ANSWER TO BLUEBOOK SCHOOL QUESTION NO. 47 The question was : What troubles may we expect to encounter zvith amplifier tubes? Upon what basis is the life of amplifier tubes reckoned, and what is it chiefly which lowers their length of efficient service? From what is current for heating the amplifier tubes derived? What is the voltage of the current with which the amplifier tubes are heated? WATCH your steps, Old Timers! For some reason not quite understandable, there were an unusual number of very punk answers to this series of questions. One Broadway man actually said, "The efficient life of amplifier tubes is only lowered by one thing ; namely, rough handling." And he is in one of our best motion picture palaces, too ! Those who passed under the wire on all counts were Frank Dudiak, G. R. Needham, Gayle Grubaugh, Leo G. Sands, Karl Friedrich, Carl F. Daugherty, Sam Goodneau, T. R. Roand, W. T. Lathrop, G T. Baldy, L. D. Felt, Bernard Hoskins, G. R. Eggleston, Bill Doe, Sam Lathrop, L. Birch, Thomas Bundy, Tom Pitkins and Matthew Sobely. They are all there were out of a great pile of answers, and even so I had to stretch things a bit to even let some of these through. I have selected the reply of Friend Birch as best suited to publication. He says : "The troubles most often had with amplifier tubes are, (a) Filament burns out, (b) short caused by filament touching the grid, (c) low emission, and (d) dirty contacts. However, the tubes have now reached such a stage of perfection that they seldom give much trouble if they are cared for properly and not 'roughhoused' or otherwise abused. Tubes will not stand abuse, though. "Amplifier tube life is reckoned by hours of actual service. A tube does not, so far as [Until further notice, all communications to this department should bs addressed to F. H. Richardson, 43-28 Thirty-ninth place, I. on Island City, N. Y.] I am able to find out, deteriorate in any degree when not in service. "Length of efficient service for tubes is chiefly shortened by two things; namely, (a) operation at voltage in excess of their normal rating, and (b) abuse in the form of rough handling. "Current for heating the tube filaments usually is derived from storage batteries, though a transformer of suitable type may be used for this purpose with certain types of tubes. The voltage for heating the tube filaments would be dependent upon the type of amplifier and tubes. It may be anywhere within a range of from one to 15 volts. In Western Electric system, 12 volts are used, derived from two 6-volt storage batteries." Friedrich gives the following voltages : W E 239A, 1 volt; UX 226, l.S volts ; UY 227, 2.5 volts; WE 205D, 4 volts; UX 245, 2.5 volts; UX 250, 7.5 volts; WE 211, 10 volts. The Arcturus "heater type" tubes require 15 volts. He gives these merely as a few examples. (Continued on next page, column 3)