Exhibitors Herald and Moving Picture World (Apr-Jun 1930)

50 Better Theatres Section May 10, 19 ' USE YOUR OWN LENS GoldE offers an UNEQUALED INEXPENSIVE SIMPLE, EFFECTIVE Way to Run Sound and Silent Film Together Requires But One Lens Put your present lens in a GOLDE Unilens Mount fitted with a GOLDE Centering Aperture Get perfect alignment and complete screen coverage at lowest cost. GoldE UNILENS METHOD NO PRISMS NO FUZZ NO BIFOCALS NO DIMNESS Installed in twenty minutes on your Simplex Projector without removing doors or cutting front plate. No cumbersome machinery. TOUCH TWO LEVERS THAT’S ALL A touch with one hand on two little levers makes the shift from sound to silent film and reverse. Made so quickly that Vitaphone and standard films may be run on the same reel and the audience never know the difference. No sleight of hand tricks to learn. NOTHING LOST The largest titles are not cut into. Neither is the action on films made to present standards. As new standard S.M.P.E. markings are released they will exactly fit the GOLDE Unilens Method. Your GOLDE Unilens Equipment will not grow obsolete. Full information on request — write at once. GoldE Mfg. Co. 2013 Le Moyne St., Chicago, 111. SOLD NATIONAL SUPPLY THROUGH THEATRE COMPANY Locating the Causes of Faulty Reproductio THE PROBLEM OF STRAYS IN DISC ATTACHMENTS In tin's, the fifth article in a series, methods of noise diagnosis are outlined for sound By HUGH S. KNOWLES on-disc equipment SOME of the problems of “strays” in sound-on-film attachments have been covered in the last four installments of this series and were treated first because of the present interest in such attachments and also because of the innumerable questions that have arisen in their operation and maintenance. Normally the problem of noises or strays in disc attachments would have been considered first because the diagnosis is usually simpler and because all strays in the amplifier and those resulting from induction or “pick up” in the input leads from the fader to the amplifier, must be eliminated before investigating those in the film attachment. Due to the comparatively low amplification used in disc attachments, or in the disc part of a dual system, many disturbances are never amplified enough to cause an audible stray in the theatre. The fact that they are present, though normally inaudible or “masked” by the sound recording, can frequently be demonstrated by turning the fader to the full-on position. In diagnosing the strays, it is usually convenient to determine those which are present under the following conditions, (a) with amplifier and speakers turned on, switch in disc position (in dual system) and fader at average setting for disc operation; (b) same as (a) but with projector and turntable running and pickup off the record; and (c) in normal operating condition with the pickup on the record. The strays in case (a), are due to the contributions of the speakers, amplifier, tubes and the input line, including the leads from the pickup to the fader, and those from the fader to the amplifier. The most common stray is a “power” hum. This was discussed in the first article of the series. On occasions there may be “clicks” and “rumbles.” If the leads from the fader to the amplifier are disconnected at the amplifier, the clicks present are very probably in the amplifier, although in rare cases they may be due to the speakers. Clicks, or “scratching” noises from the amplifier, may be due to poor intermittent contacts, to faulty condensers, or to the tube. If a three-stage amplifier with a 227-type tube in the first stage, is used, the trouble is very apt to be in this tube. These will be considered more fully lab; in connection with the maintenance i amplifiers. If the clicks stop when the input leai to the amplifier are disconnected, tl stray is being picked up by the inpif leads. Some of the sources of outsit; ( strays, such as sputtering arcs, mote generator sets, sign flashers, etc., web enumerated under the second group t strays in film attachments. These ai very much less common in disc attacl ments, since they have to be much moir powerful to cause a stray that can l heard in the speakers. If the installation has been made i a good substantial booth, there is rare! a rumbling noise in the speakers whe the turntable and projector are not i operation. Where there is one, it is du to the vibration of the amplifier jarrin the tube in the first stage (usually 227-type) and producing a “micrc phonic” noise. This may be regeneri tive, or built up when the monito speaker is in operation, and regeneratio may be checked by turning the monito off, as mentioned in group (c) unde film attachments. The remedy lies i the substitution of another tube wmc is less mierophonic, in protecting the air plifier from the vibration, or in mini mizing the vibration of the machinerj The last is to be preferred, since thi vibration is much more serious if in volving those troubles considered unde group (c), below. When the strays from the abov sources have been eliminated or mini mized, the projector and turntabl should be started. Any clicks which re suit from starting and which last fo only two or three seconds, are probabl; I due to sparks at the centrifugal startin; switch in the induction motor used ir most “independent” devices. Othe noises which are coincident with sput tering of the arc may be due to indue tion, although this is rare in disc instal lations. Careful shielding of the inpu leads will eliminate both. In booths hav ing a light sheet metal covered planl flooring, there may be vibration enougl from the machine to cause a microphonii rumble of the type described under (a) Nearly all strays which harass the ex hibitor and projectionist fall in grouj (c) and are present only when the ma chine is in operation and the pickup i: