What happened to my tube ?

[Mariocò]

Hi guys, I'm kinda new here...sorry if posted into the wrong section !

I've got a question for you all, please don't leave me with this doubt in mind

I purchased an as-new Mark V head, and yesterday I noticed this strange kind of colour into one of the tubes..



It lights much less than the others, and I don't know if it's normal that ' white fog '..is it burned ? How can I recognize it, tho ? Is it normal into this kind of tubes ? I've normally used el34's before ( but never in this amp )...

Thank you a lot in advance guys...

( sorry for my english, but I'm italian )

 

[domct203]

Welcome to The Board, and Happy New Year.

That tube is no longer usable. The white "fog" is actually the getter flash, which is normally silver in color in a healthy tube. It has turned to white because the tube has lost all it's vacuum and the getter has reacted to the oxygen that has entered the tube. The heater filament will soon burn out making the tube totally dead. It should be replaced right away before a short develops and possibly causes damage to the amp.

The tube has lost it's vacuum either from a defect in manufacture, or from a crack in the glass. If there is no appearent crack, the leak is most likely somewhere under the plastic base.

Dom

 

[Mariocò]

Welcome to The Board, and Happy New Year.

That tube is no longer usable. The white "fog" is actually the getter flash, which is normally silver in color in a healthy tube. It has turned to white because the tube has lost all it's vacuum and the getter has reacted to the oxygen that has entered the tube. The heater filament will soon burn out making the tube totally dead. It should be replaced right away before a short develops and possibly causes damage to the amp.

The tube has lost it's vacuum either from a defect in manufacture, or from a crack in the glass. If there is no appearent crack, the leak is most likely somewhere under the plastic base.

Dom

happy new year to you, and thanks a lot for the answer !

so, I should replace it...I've played for 15 minutes the whole amp with this tube in this condition...I've noticed it just later...it's a problem ?

P.s.: the 4 power tubes should all light in the same way or not ? Just curiosity..


aaaaaaaaand...I'll just replace this one...it's not a problem, right ? The important thing is that it has to match with the respective tube indicated in the manual...

Thank you again !

 

[domct203]

Yes, you can replace just that tube as long as the new tube's color code matches it's mate in the pair.

Mesa's are built tough, I'm sure the amp is fine. I would not play the amp until the tube is replaced, just to be safe.

Usually the powertube heater glow will be approximately the same across all the tubes, however, the level of glow is not usually an indicator of the tube's health, unless of course there is no glow at all.

Dom

 

[Mariocò]

Thank you a lot, man ! I've really appreciated your help..


Just another question..how can I know if the preamp tubes work fine ? Only if are not microphonic and/or I can't hear any hum or something like that from the speakers ?

Thank you so much again...

 

[domct203]

Thank you a lot, man ! I've really appreciated your help..

Just another question..how can I know if the preamp tubes work fine ? Only if are not microphonic and/or I can't hear any hum or something like that from the speakers ?

Thank you so much again...

Correct, as long as the amp is functioning correctly and not making any strange noises (whoosing/crackling/popping/ringing etc) the preamp tubes should be fine.

Dom

 

[Mariocò]

So, I've turned the amp on....I think every tube lights up normally...I guess..



I've seen they are all 6L6's grey..but it seems just like aren't available anywhere here..( not just in Italy )...just in case...what colour would be good ? Are the colour differences eventually noticeable to my ears ?
Oh, and...as I've written, I've got all power tubes grey...but If I buy a couple of red/yellow ones to replace just the two grey according to the right positions as described into the manual, will everything work fine ? I mean, there would be two grey and two red/yellow ( the new ones )..

Thank you again, so much..


( sorry again for my English.. )

 

[domct203]

The color codes are simply to group the tubes into pairs/quads. I do not hear any difference between color sets.

Dom

 

[Mariocò]

The color codes are simply to group the tubes into pairs/quads. I do not hear any difference between color sets.

Dom

so you're telling me that I can have a pair of grey ones and a pair of red ones ?
No troubles ?

 

[domct203]

The color codes are simply to group the tubes into pairs/quads. I do not hear any difference between color sets.

Dom

so you're telling me that I can have a pair of grey ones and a pair of red ones ?
No troubles ?

Yes that is correct.

Dom

 

[shytfayse]

The color codes Mesa uses is to match the output tubes by how much quiescent cathode current flows with a fixed grid bias, which all Mesa's have. The red tubes are the coldest tubes Mesa offers. The grey is in the middle.

Mesa uses a small slice of possible output tubes that are available by their current manufacturer that will work in their fixed-biased amps and their color coding divides that small slice into ever littler slices. There is a very subtle difference between the colors, but, there may be a substantial difference between a red (coldest) and a white (hotest).

Maybe I'm a dummy - doesn't Mesa ship to europe? If so, can't they get some greys to you?

My recomendation, if you can't get any more grey tubes, is to get two reds and use them in positions 1 and 4 and leave the two greys in position 2 and 3. That will at least keep your power section balanced.

- Pat.

 

[Mariocò]

Thank you for your answer, too....

at the end of this story I've done something unexpected...I've bought two pairs of blue ones....I'll replace them all ! Don't want troubles in any way and it's always a good thing to have some replacements....I'll keep the grey just in case of tube glowing.


I'll post here the eventual tonal differences..

 

[shytfayse]

I think you did the right thing - not knowing the number of hours on the original output tubes.

The blue is one step below white, or, the fifth hottest tubes mesa sells. I think you will be happy.

- Pat.

 

[Mariocò]

guys I've swapped old tubes and I've replaced them with the blue ones...

honestly, it was a little bit difficult to change them, but making LOT of pressure I did it

about the sound..well, sincerely, I can't do a comparison because I didn't A/B'd them...I've just played with greys a week ago, and now I play with blues..surely the volume it's insane, but I think is because of the amp itself. Grail tone, however.

Just one thing I've noticed...these blue lights really a lot...surely more than grey...possible ? Any thoughts about that ?

 

[shytfayse]

Decribe the light. Blue, orange, red? Blue glow is OK. The only other part of the tube that should glow orange or red is the heater filament. Try this: turn the amp on with the stand-by off, watch the tubes and turn the stand-by on. Besides a blue glow in the vacuum, there should be no other part of the tube that starts to glow or change color. Post another picture of the amp on stand-by and the amp off standby if you think there is an issue.

- Pat.

 

[Mariocò]

guys sorry if I didn't take the grill out, but I was hurry


V1 - V2
V3 - V4
Recto tube

I just think everything it's ok and tubes light up correctly. The sound still incredible, grail tone for sure.
Just one thing..I use the output and solo knobs..( effects loop on )...on hard bypass, with indipendent volumes for each channel I see that master knobs are way more responsive...the volume ACTUALLY works a lot, and helps to saturate more...with effects loop on and output knob, the masters seem to be less responsive and the volume increase seems to be less..( especially for channel 3 )...is it just me ? What do you usually do ? What do you suggest ? It's just me again, or on hard bypass you can get more gain out of ch.3 ?

thank you all, guys