Radio age research, manufacturing, communications, broadcasting, television (1941)

Old Tubes Made New RCA VICTOR ENGINEERS REBUILD TRANSMITTER POWER TUBES TO AID BROADCASTERS DURING REPLACEMENT SHORTAGE By L. W. Teegarden Manager, Tube and Equipment Dept., RCA Victor Division EARLY in 1942, studies made by the radio industry indicated that GO to 70 per cent of the na- tion's broadcast stations might be driven off the air unless renewal tubes were made available to them. Helping to keep broadcast stations on the air in the face of a threat of silence for lack of replacement tubes is the part played by RCA Victor Division engineers. The tube and equipment depart- ment met the emergency on two fronts. The first front was devoted to obtaining from amateur opera- tors, already silenced by the war, the power tubes no longer in use. The second front tackled the prob- lem of salvaging the larger types of power tubes through a rebuild- ing program. Salvage Larger Types In a program to obtain the maxi- mum life of tubes still in service, an advertising campaign was di- rected to broadcasters. One of these advertisements, ad- dressed directly to amateurs, sug- gested that they sell their idle transmitting tubes to their nearest RCA tube distributors thus making them available to commercial broad- casters. This was followed by a broadcasting trade advertisement suggesting that stations contact RCA tube distributors regarding the availability of such tubes. As a consequence of this cam- paign, hundreds of tubes owned by amateurs began to pour into the hands of RCA distributors and be- came available for broadcasters. Some had never been used. But, in a spirit of patriotism, their "ham" owners brought them in to RCA distributors as a contribution to the war effort. A number of operators wrote directly to the company de- scribing what tubes they had for sale. A list of these offerings was sent to RCA tube distributors and broadcast stations. Meanwhile, RCA engineers were attacking the problem of salvaging larger types of tubes, which use substantial quantities of critical materials, through rebuilding. The rebuilding program does not justify itself in times of peace, when mate- rials now critical are plentiful and relatively cheap. It calls for com- plete dismantling of tubes returned by the broadcasters after the tubes were worn out electrically but not mechanically. The usable parts of such tubes, together with small amounts of necessary new material, were then put through the com- pany's regular manufacturing proc- esses of assembly, aging and test- ing. All of that sounds simple, but what it called for was a reversal of the assembly line procedure, in tak- ing the old tubes apart, and the de- velopment of new techniques in re- building them. It was a reclama- tion program that could not be conducted on an individual basis. In other words, it called for a pool- ing of old tubes. In the rebuilding process the parts of each single tube lost its identity. The one the broadcaster got back might contain parts from any others. THE FIRST STEP IN REBUILDING AN IN- OPERATIVE POWER TUBE IS TO CUT OPEN THE CLASS BULB. AS SHOWN HERE. One of the most difficult parts of the job, of course, was getting the materials. Speed was essential, but the work could not be hurried. As a first step, for example, the broad- casting station had to obtain a pref- erence rating to accompany the re- turn of an old tube and his order for a rebuilt one. Since radio tubes contain quantities of copper, tung- sten, molybdenum, nickel and other metals now obtainable only on WPB priorities, all orders were contin- gent on the amount of material thus obtainable. After all these problems had been .solved, the tubes had to be tested to make certain that they would stand up under ac- tual service. These tubes were tested over a period of months in RCA services to insure that rebuilt tubes would give good service. Keep Stations On Air All of this took time, but patience and skill triumphed and, early last Fall, RCA Victor was able to notify broadcasting stations that it was ready to help keep them on the air with rebuilt tubes of types listed. It might be noted here that in many instances the station sending in its order was reduced to a single spare tube before the failure that made the order necessary. If the rebuilt tube had not been available and the [12 RADIO AGE