53KU Cossor Yellow Print label rare GZ37 large shoulder shape matched pair valves tubes tested 100%

Description

The GZ37 aka 53KU is an indirectly heated full wave rectifier and together with the U52 the 53KU and GZ37 are the most sought after valves here at AM.

Looking at the Cossor 53KU there are two separate valve in one envelope

Cossor started production of the 53KU circa 1958

Pair of Cossor yellow print 53KU equivalent GZ37 and CV378  grey ribbed plate with large getter located in the middle of envelope.

Brown base with yellow print on glass! Both have same design and construction.

A well engineered valve that lasts longer than any other counterpart, delivering excellent rectification.

Clean top and in great shape.

Tested 53KU with AVO VCM 163 with A1=A2 100% emission