From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter to the General Electric Co. Ltd. regarding discrepancies and test results for a U.4 Rectifying Valve.
| Identifier | ExFiles\Box 41\2\ Scan039 | |
| Date | 11th December 1926 | |
| X3646. EFCL/T. 11th December, 1926. Messrs. The General Electric Co.Ltd., Magneto House, Kingsway, London, W.C.2. Dear Sirs, Re U.4 Rectifying Valve. The valve itself is marked 5.0 volts, but the voltages given on the label on the box and in the leaflet are 5.6 to 6.0, which we presume is correct. The maximum rectified current is given on the valve box as 50 m.a., but on the leaflet it is given as 15 m.a. though the curve itself for a filament voltage of 6.0 and an R.M.S. plate voltage of 220 shews 50 m.a. on short circuit output. The curves of rectified output (i.e. output volt-ampere characteristic) given on the leaflet appear to drop to zero at too low a D.C. voltage. Observations taken on two of these valves shew (similar) results, which are not in agreement with the curve given on your leaflet, but much more like what one would expect on principle. In the case of one valve the filament was maintained at 6.0 and the R.M.S. A.C. supply volts were 189 at 50 periods. Starting at a back D.C. voltage of 204 and working downwards, the m.a. observed on various voltages were in accordance with the enclosed sheet of results. After arriving at zero back voltage at which 49 m.a. were initially obtained from the valve, D.C. voltages were again increased in steps and again decreased, with results also indicated. Finally, the back D.C. voltage was fixed at 124 and observations were taken at intervals of a quarter of an hour each in order to observe the recovery of the emission which had been reduced by working with a small back D.C. voltage, the A.C. volts being switched on for a short period only each quarter of an hour in order to take a reading, but the filament volts being | ||