My Subway Blues Stinks!

[bryantkh]

Hey guys, bought a used Subway Blues last week. I love the tone. Well, it started getting a bad crackle, so I replaced the EL84s and the noise is gone. The tone sounds even better than before. Now the amp has a bad smell after it has been on a minute or so. It seems to get weaker the more I play, and each time I turn it on its weaker.

Anything to worry about?

 

[94Tremoverb]

Yes. If it's getting quieter as well it sounds like something is overheating. It could be as simple as a bad EL84 - just because they're new means nothing unfortunately. Have a look round the back and see if one or both is visibly getting too hot - ie any sign of red glow on the outside of the grey plate structure, or very bright orange glow (much brighter than the usual filament glow) inside it.

'Hot' smell and a loss of power, clarity and headroom is typical of an overheating tube. Unfortunately, sometimes unusually great tone is too - just before it fails.

If there is a tube overheating, it could be just the tube, or possibly something wrong with the socket. That might explain the crackling noises before too - if there was a poor contact on the grid pin that is now completely open.

 

[Old BF Shred]

Did you use Mesa el84's? and if not, did you get the bias and idle current checked? :?:

If not, you could be on your way to a very expensive repair bill!
Better go see a tech....good luck!

 

[Don]

If it's only the smell that's weaker (not the amp's volume), and the plates aren't glowing, it might just be the ink on the tubes burning off. I had a set of new Mesa 6L6 power tubes stink for a while when they were brand new.

I'd still check the bias.

 

[bryantkh]

Thanks guys. There is no change in the sound at all, played for an hour last night. The smell just gets weaker. They are Mesa tubes. I looked last night and didn't see anything out of the ordinary. I will look again. Maybe I should plug a different old pair of EL84s in?

Could this just be the ink then?

 

[94Tremoverb]

Oh, you meant the *smell* is getting weaker, not the sound...



My bad.

It is probably just solvents in the print cooking off, but I would still check the bias current. The tubes shouldn't really be getting hot enough to actually burn the print that quickly from new. Discolored print is usually a sign that the tube has been running too hot for a long time and is near enough dead.

6L6s and EL34s often smell much worse when they're new because there are more glues and plastics in the bases - but EL84s shouldn't really. Some companies stick labels on them too, which can really stink. Putting labels on the glass is bad practice because it causes uneven heating of the bottle, you should really remove them if they have any - you may need some solvent.

 

[Old BF Shred]

Yea, the smell of "new tube ink" has to be way better than the smell of "transformer gonna die".... :lol: :lol:

 

[Monsta-Tone]

Yea, the smell of "new tube ink" has to be way better than the smell of "transformer gonna die".... :lol: :lol:

That is a sucky smell!!!!!!!!!!!!!!!
If the smell gets weaker, then you are probably ok.

A lot of times, like 94tremoverb said, the solder joints get weak on the smaller Mesa amps using EL84's.
The sockets are mounted to a small circuit board that eventually gets a little warped and funny looking. My Maverick is from the mid 90's though and has the same basic circuit board. It's still going really strong!

If something in the amp were going, the sound should get weaker or thinnner. And....burnt transformers, resistors, boards, etc., have a smell that is unlike any other! If something were burning in the amp, you would know because the smell would get stronger.

Look in the back of the chassis if it has the cooling holes. If it's dusty in there, you might get a can of compressed air that is used to clean out computers. Blow it in there and get rid of some of the dust. This may be what's causing the smell too.