The 5651A is a small, special quality voltage reference designed for use in stabilised DC power supplies.
The striking voltage is 115 Volts and the maintaining voltage is 86 Volts. For a tube current variation of 1.5 mA to 3.5 mA. The low current rating is typical of a voltage reference tube that is not designed to supply current to a controlled stage. The current would be kept as constant as possible to maintain the exact operating voltage.
The original Type designation is in the box at the top with the Hewlett Packard information overprinted.
The valve was made for HP by RCA.
The HP logo.
The thin glass tube envelope is 18 mm in diameter and excluding the B7G base pins, is 47 mm long.
