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So, does anybody know what that greasy, sooty looking deposit is that forms inside the envelopes of EL84/6BQ5 tubes?
Supposedly it is common with many of the "good" EL84's, such as the Mullard, Amperex, RCA's, etc. I have a few examples of each of these and sure enough, there is a nasty looking substance that is deposited on the bottle near any openings in the plate, or around the mica spacer at the bottom of the plate. The new current production EL84's I have don't have this deposit. I understand it is a "good" thing, since it is associated with the most well-loved EL84's. I also understand that it is not visible until the tubes have been in operation for a little while.
Also, a lot of the European tubes have that odd characteristic of "flashing" momentarily when the filament is first turned on. Mullard and Amperex manufactured 12AX7's in particular. This also must be a "good" thing, since these tubes are the cream of the NOS crop. These tubes flash every time they are turned on, not just the first time.
I assume there must be some sort of gas (or ??) inside the tube that fires every time the tube heats up. Could this be something put in the tube to enhance the vacuum or bind up any contaminants inside the bottle? Could the flashing and the sooty deposit be related in the sense that they are something put inside the tube on purpose to enhance the performance? Also, the tubes that I have with the sooty stuff don't flash, and vice versa.
What do you guys know about this?
-Boots
Supposedly it is common with many of the "good" EL84's, such as the Mullard, Amperex, RCA's, etc. I have a few examples of each of these and sure enough, there is a nasty looking substance that is deposited on the bottle near any openings in the plate, or around the mica spacer at the bottom of the plate. The new current production EL84's I have don't have this deposit. I understand it is a "good" thing, since it is associated with the most well-loved EL84's. I also understand that it is not visible until the tubes have been in operation for a little while.
Also, a lot of the European tubes have that odd characteristic of "flashing" momentarily when the filament is first turned on. Mullard and Amperex manufactured 12AX7's in particular. This also must be a "good" thing, since these tubes are the cream of the NOS crop. These tubes flash every time they are turned on, not just the first time.
I assume there must be some sort of gas (or ??) inside the tube that fires every time the tube heats up. Could this be something put in the tube to enhance the vacuum or bind up any contaminants inside the bottle? Could the flashing and the sooty deposit be related in the sense that they are something put inside the tube on purpose to enhance the performance? Also, the tubes that I have with the sooty stuff don't flash, and vice versa.
What do you guys know about this?
-Boots
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