Here for sale an absolutely awesome and super rare Mullard fat brown base GZ34 5AR4 F31 model.

code F31 B9H

Tests results  104 % and 104 %

Made in the Mullard Blackburn factory in August 1959 in Great Britain,

As testified by the very hard to see Mullard date and factory code which is intact ,but need very good light and angle or magnyfing glass to be well seen. I tried to photograph it the best I could .. Not easy but the Mullard Balckburn code is well there.

Fully tested and perfectly balanced

Excellent perfect condition, super strong and can't be better balanced. It has a splendid large mirror liker shiny getter flash.

Highly sought after early f31 model, with smoothand double O Getter.

Probably new unused , sold as new or very few use.

Considered as one of the very very best and more robust GZ34 ever made .

Amazing construction, real master piece of tube engineering .

Get the best of your power section.

 No short
 No leaks  no issue                      
  I COMBINE SHIPPING ,

  SO PLEASE HAVE A LOOK AT MY OTHER ITEMS AND SAVE .

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.

Thank you for your interest