Tips and Jottings

Radio Record, Volume IV, Issue 49, 19 June 1931, Page 17

Tips and Jottings

"THE holes in a panel through which the fixing screws are driven to secure the baseboard to the panel are best drilled when the panel and baseboard have been placed in their correct relative positions. If- fixed together

outside the eabinet they may not make | a smooth fit such as would otherwine be te. case... a N excellent device. rechten the shorting of leads passing close to or through a screening box, is valve tubing such as is used for: bieyele ‘tires. , [sn frequency per ‘second ‘correspond: ing to the lowest note on the piano is 26.6, and that of the ‘highest note 4096. GETS that "have. been out, of action for a month or so often mysteriously develop bad contact,-due to loose terminals, ete,, so they should be gone over carefully with pliers before being Placed in’service again. WHEN wiring up 4 multi-valve set, it is a good plan to check valve holders, ete, for continuity. before mounting them in place, as the little time lost is more than justified when it is remembered how’ long such a small fault may take to remedy in a com-petely-buike set. N old ‘shaving brush. kept on hand when drilling, filing, ete., is done, will -be found almost for "clearing up" as one goes along. BEFORE mounting a new valve holder on a baseboard run over the terminals, etc., with a screwdriver or pliers, to ‘make sure that all contacts are good, as.there is nothing more annoying than to find a well-soldered and ungetatable valve holder has developed a. loose contact that could have been prevented by such timely attention. FAILING separate tappings for all the valves in-a powerful set employing a pentode, the tendency to motor-boat-ing may be overcome by the use ‘of. a decoupling device -in the circuit of one of the valves run from the common. tap, "yea. [* you are making a set in which a tuning coil is placed somewhere near to a screen, be very careful to see.that you keep it the correct distance from the screen, for if it is too close’ you are almost certain to lose selectivity. HEN buying a new rectifier valve for your eliminator, be sure .to find out whether it needs .a full or half-wave valve. . A full-wave has two plates against. the one of half-wave, -Most eliminators use. full-wave or filamentless rectifiers.