Description

Quantity One Vintage Sylvania 12B4 Vacuum Tube NOS NIB *TESTED* New In Box New Old Stock Tested as shown on Hickok 533 Dynamic Mutual Conductance Tube Tester Box worn from years of storage – A low mu 9-pin miniature tube, the 12B4 was originally designed for TV sets for use in the vertical deflection unit. But of course it is usable for other applications as well. The 12B4-A is a single indirectly heated triode. The pinout is shown on the left. It has a center tapped heater, which allows to heat it either from 12.6V or by utilizing the center tap and paralleling the halves from 6.3V. The only difference between the 12B4 and 12B4A is the controlled heater warm up in the latter which allows it to be used in a series heater string with other tubes which need 600mA heater current (or 300mA if the series connection is used). Being a low mu triode it has an amplification factor of only 6.5 which is coupled with a plate resistance of a only 1kOhm. This results in a healthy transconductance of 6300 micromhos. The 12B4A is designed for rather high current operation with peak currents allowed to reach 100mA.