Rare 50's NOS NIB SYLVANIA 5U4GB 5U4 GB BLACK PLATE double SIDE O GETTER ! perfectly balanced and super STRONG. NEW !

Here is a rare superb and perfectly balanced NOS NIB Sylvania 5U4GB made in 1959.

Early version : Black plate, double side big O getter.

Tests results   119 %   118 % .

Perfectly balanced and super strong.
Superb condition. Made in the USA
Large superb shiny getter flashes. 
Very robust and efficient, long lasting 5U4GB.

New with original box.

The perfect rectifier.

Get the very best from your amp.

Fully tested on Jackson 648S for

Filament

Circuit

Shorts

Plate

Life test...

The Jackson 648. It is definitely one of my favorite tube testers. While it does not employ a mutual conductance test circuit, it does use an advanced emission circuit that applies separate element voltages to each tube element, and separate load circuits are also used. “These voltages and loads have been carefully selected for each tube to meet most ideally the normal operating condition of the tube.” (Source: 1950 Jackson catalog.)

In my experience, the Jackson circuitry is very effective, and often will surprise you with accuracy that approaches Hickok’s coveted “mutual conductance” test method. ( Source tubesound web site.)

I do my best to test and describe the tubes the best I can.

Note that test results may vary from one tester to an other so this must be taken as an indication, although my Jackson is regularly tested for calibration.

 Photos are part of the description you get what you see.