The 5Y3 is a medium-power directly heated rectifier

Rectifier

A rectifier is an electrical device that converts alternating current , which periodically reverses direction, to direct current , which flows in only one direction. The process is known as rectification...

 vacuum tube introduced by RCA

RCA

RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...

 in 1935. It has found wide use in tube radios and early guitar amplifiers (of the Fender Champ type.) It is virtually identical, electrically, to the four-pin type 80 tube, but with an octal

Octal

The octal numeral system, or oct for short, is the base-8 number system, and uses the digits 0 to 7. Numerals can be made from binary numerals by grouping consecutive binary digits into groups of three...

 base.

The success of the 80 and 5Y3 led to the development of many similar rectifier tubes of both higher and lower power ratings, including the 5V3, 5W3, 5X3, 5Z3, 5U4, and 5Z4. The epitome might have been the 3DG4 of the 1960s, with a full 240-milliamp capability.

Currently, a plug-in replacement is being manufactured by Sovtek

Sovtek

Sovtek is a brand of vacuum tube owned by Mike Matthews's New Sensor Corporation and manufactured in Saratov, Russia. They are often used in guitar amplification and include the popular variants of the 12AX7, EL84, EL34, and 6L6 models...

in Russia, which has very similar specifications, but is indirectly heated, and can support currents up to 144 mA, versus the 120 mA of the original. However the Sovtek 5Y3 is not a true 5Y3. It drops less voltage than vintage 5Y3s, and may cause voltages to run too high.

External links

• http://www.dougstubes.com/ruby-5y3gt.html Chinese plug-in replacement
• http://boozhoundlabs.com/howto/pdf/5Y3GT.pdf General Electric datasheet