Cloudy Rectifier Tube

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I have some old Mesa vintage preamp tubes that have similar appearance but not as black, more white but they sound great. However, I would replace the rectifier tubes (both of them) as it is uncertain of the age of the tubes. General rule of thumb with the rectifiers, replace them when you replace the power tubes, also change the PI tube too.

My Mark V was having issues, noticed arcing in the rectifier tube from bottom area ut to the getter on top. They do not last forever and once they degrade it does not matter if your amp has silicon diodes since the tube rectifiers run parallel and are not switched off with silicon diodes are active.

Either the Mesa 5U4GB or the EH5U4GB (essentially the same) will work fine. I have seen a used DR for sale at Sam Ash and noticed it had the larger coke bottle 5U4G and they seem to fit fine. I would not be able to use the 5U4G in the Mark V due to its size since the cage would be resting against it.
 
Worth changing as Bandit suggests. Not expensive to do, and not worth the risk of failure :wink:
 
The highest possible vacuum is desired in a tube. Remaining gas atoms will ionize and conduct electricity between the elements in an undesired manner. In a defective tube residual air pressure will lead to ionization, becoming visible as a pink-purple glow discharge between the tube elements, If a tube develops a serious leak in the envelope, this deposit turns a white color as it reacts with atmospheric oxygen.
 
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