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Tube amp repair question....

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tube amp
3K views 5 replies 3 participants last post by  satchboogeyman 
#1 ·
I noticed that my old Fender tube amp started sounding different. It seems to have less power and breaks up much easier.
So I just had a look at the tubes and I notice that one 6L6 is lighting up but is cool to the touch, the other 6L6 is very bright and very hot to the touch.
Would this be a possible bias problem? Can the bias just change like that? or would it most likely be that the tube thats not getting hot has just started to die? or could it be something else? I do have spare 6L6's but I'm always a little weiry about pluging in a mismatched set without haveing the amp biased.
I recently had a new rectifier tube installed if that makes any difference.
 
#2 ·
I am no authority but I guess it could be bias one tube is drawing more voltage but I am leaning towards the tube is shot. I would order a new set of power tubes or get a full replacement set. I usually buy from Eurotubes. Hope this helps I am sure someone with more knowledge wil chime in.
 
#3 ·
if its glowing red more than likely the tube is on its way out. Thats a tale tell sign..

time to pony up, empty the wallet and go buy some new tubes.. Not a new tube but TUBES Plural, what position is the hot tube in before or after the cool tube, by one going out its going to make the other work hard and its a matter of time till its gone too..

And then to top it all off, take it to a professional and have him rebias it, most manufactures under bias the tubes to last longer, you would be surprised at your new tone when its biased correctly.
 
#4 ·
The amp was biased when the last set of tubes were installed. And yes it does make a big dif. when it's done correctly. I told him to go ahead and bias the amp hot too so maybe thats why the tube went. It's been about 2 years since the new tubes were installed.
I'm going to call the tube amp guy today and see if I can drop it off.
 
#5 ·
LOOSE TUBE!!! lol I decided to wiggle the tube that was not getting as bright, and I heard a static type sound, like I heard when this problem started and presto! both tubes lit equaly, sounds like it should. I think there was moisture in there or a bad contact somehow.
 
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