I've just replaced a Mesa branded 12ax7 valve in my Mini Rec after discovering a hairline crack that runs pretty much the whole way up. This was the second one that i've found like that (the first was also Mesa branded), the first one had 3 cracks in it and i noticed that after a while of it sitting on my desk that it lost it's vacuum and is now filled with a white powdery substance.
As far as i know they are the original valves that were in it since new (2012), is this normal for valves that are past their best or do i need to start thinking about getting the amp checked over?
The others all seem fine (they aren't original, a mix of Tung sol and JJ).
Comments
If it was mine, I would totally re-valve it to be sure. I've had good results with JJ 12ax7s and Mesa biased TAD's
There was for a very short time a problem with the 12BH7 in the original HT-5. In a few cases the valve was found to have cracked and filled with the white ***t. The problem was put down to overzealous tightening of a cable tie on the cableform exiting the valve base. I used to snip off any I saw.
Both valves are now of course on the PCB.
Dave.
Just strange how it's happened to 2 (of the same make).
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