The quality of the electron beam in electron defraction tube S (1013889) is affected by the resistance between sockets C5 (cathode) and F4 (heating filament) on the tube. For optimum results, the resistance needs to be 390 kΩ. Tube holder S (1014525) is accordingly designed such that this resistance is present.
Older designs feature a much smaller resistance and need to be modified in order to work with the new S-series electron deflection tube 1013889).
Tube holders affected: U18500, U185001, 1000610
![Replacement Circuit Board for Tube Holder S, 4008573 [U99999-611], Replacements](/imagelibrary/U99999-611/U99999-611_01_Replacement-Circuit-Board-for-Tube-Holder-S.jpg)
![Tube Holder S, 1014525 [U185002], Electron Tubes S](/thumblibrary/U185002/U185002_01_140_140_Tube-Holder-S.jpg)
![Electron Diffraction Tube S, 1013889 [U185711], Electron Tubes S](/thumblibrary/U185711/U185711_01_140_140_Electron-Diffraction-Tube-S.jpg)
![Helmholtz Coils S, 1000611 [U185051], Experiments with Electron Tubes](/thumblibrary/U185051/U185051_01_140_140_Helmholtz-Coils-S.jpg)
![Thomson Tube S, 1000617 [U18555], Electron Tubes S](/thumblibrary/U18555/U18555_01_140_140_Thomson-Tube-S.jpg)
![Deflection Tube D, 1000651 [U19155], Electron Tubes D](/thumblibrary/U19155/U19155_01_140_140_Deflection-Tube-D.jpg)
![High Voltage Power Supply 5 kV (115 V, 50/60 Hz), 1003309 [U33010-115], Power Supplies](/thumblibrary/U33010-115/U33010-115_01_140_140_High-Voltage-Power-Supply-5-kV-115-V-5060-Hz.jpg)
![Replacement Part: Critical Potentials Tube S with He-Filling, 1000620 [U18560], Electron Tubes S](/thumblibrary/U18560/U18560_01_140_140_Replacement-Part-Critical-Potentials-Tube-S-with-He-Filling.jpg)