Archives for March 2012

Testing-Device for GU74b / 4CX800 tubes

It seems that the exchange of GU74b / 4CX800 tubes in Amplifiers like Alpha91b, Acom2000A and Acom1000 is of more interested than originally expected. In my post on how to replace the tubes of an Alpha91b I explained in depth why it is so important to recondition, to “getter”, the tubes at least 24 hours before any other voltage can be applied. Often amplifiers apply automatically HV and grid voltages which makes them unsuited for the gettering process. My Buddy Matthias, DK4YJ built recently a simple device which makes the heating and testing of tubes much more convenient.

[Read more…]

Customs break my tubes (4CX800 / GU74b)

A friend of mine recently was very generous and sent me four used 4CX800 / GU74b which he didn’t need anymore. The tubes where traveling a while and through several non-EU countries. Today the parcel finally arrived. I have already heard wild stories about customs, but I didn’t expect this: Customs drilled holes in two tubes and later opened them with a saw. Checkout the pictures.

[Read more…]