Changing Valve Bases

Radio Record, Volume II, Issue 7, 31 August 1928, Page 31

Changing Valve Bases

Ba W. H. Potter, Hora Hora, writes as follows :-- HE following successful method of changing the English base of a wellknown valve and the fitting of an American UX base thereto, may be of in‘erest to constructors. Care must be taken in manipulating this change-over, but it is worth while: in many cases, there being less losses with a vaive fitting its standard holder than one with an adaptor fitting a foreign holder. First dissolve the compound holding the base to the valve, by immersing the valve in warm water. This may take an hour, and when the valve can be freely moved about in its base, the fine wire leads from the glass may be unsoldered from the base prongs. Po not twist the valve in the base or the wire leads may be broken. Valve prongs are hollow, and to unsolder the leads that come through to the ends of the prongs from the glass, hold the valve base in one hand and the glass portion in the other. Now place the valve, prongs downward, on a very hot metal plate, simultaneously melting the solder at the end of each prong. Gently lift the valve with its connecting wires, straight up out of its base, and the valve and its base are separated. Now check the valve leads as they come through the glass, and set them in position to drop through the prongs of the new base in their correct positions. These connections can be _ easily traced through the transparent bottom ends of most valves. . Possibly one or more leads from the valve may be found to be too short to go through the prongs of the new base, in which case, longer pieces of the ‘same gauge wire should be joined about half an inch or so from the glass. Here again, use care, or the original leads may break where they leave the glass. ey changing from an English base, the writer used an old base from a UX 200A valve, which was slightly shorter in length, so that no joints had to be made. Remove the solder from the ‘prong ends of the new’ base, and gently fit the valve into it, carefully guiding the valve leads into the prongs, pulling gently on the léads when they appear through the prongs. Now independ: ently solder each wire into its respective prong. heatly rounding off the solder at the end. This can be finally

finished off with a file and fine glasspaper. The next thing is te cement the valve itself to the base, and this is easily done. by running a small quantity of secotine- round the edge of the glass where it fits into the base. Now ecarefully mount the complete valve in a hélder, base downward, and after covréctly. adjusting the glass to its proper position, allow it to set for 48 hours, wheu it.should be solidly fixed ani ready for normal handling. This secotine method is very effec- . tive, and may be applied to any valve that is loose in its base..