Question about tube's life

[nismofreakish]

Hi guys!

I’m running a Mesa Single Rectifier with the same tubes for about 2-3 years (about 3 rehearses/week) and I was wondering if there was a real danger for the amp if I keep them a little while longer. Would it damage my amp if one (poweramp or preamp) dies during a gig?

I have a backup kit, but since it’s not cheap, I’d like to use it only if my actual tubes really need it. I have a gig in about two weeks, nothing big and I'm not planning swapping them for it, but I was wondering if...

Any input?

thx!

 

[Triple Cheeseburger]

potentially. if a tube goes it can sometimes (not often) take out a resistor or two depending on how the tube fails. i think its good maintenance to change tubes semi-regularly, like changing the oil in your car i guess. it can also breathe new life into a "dull" sounding amp if that makes sense.

 

[94Tremoverb]

Bear in mind that the most common time for a tube to fail is *right after you've put a new one in the amp*. Which I know is not what most people expect! Even when they've been tested, manufacturing defects are common and not entirely weeded out. So if your amp isn't actually sounding bad, I would *not* change the tubes just before an important gig. They can of course fail without warning at any other time too, but age has surprisingly little to do with it. When they get old they will start to sound dull and lose power before the risk of failure really increases again right at the end-of-life.

Preamp tubes can't really damage the amp if they fail. Power tubes can take out a screen resistor, although as Cheeseburger said it's fairly rare. Just make sure you carry at least a couple of the correct fuses as well as spare tubes, or the spare tubes probably won't help! And never, ever, for any reason, replace the fuse with a higher value or wrap it in foil or anything else like that to 'get you through' - you'll just fry your amp much more seriously and it still won't get you through.

 

[thunda1216]

+1

I've got one amp that is over 30 years old that still has the tubes that came in it, and it has a lot of hours on them. All my amps have lots of hours on the tubes. My Heartbreaker has 7 year old winged c power tubes, and it gets about 40 hours a week. Every now and then a tube fails. Don't lose sleep over it. Play the amp and carry a couple of spares. My spares have dust on them, by the way.

 

[nismofreakish]

Thx for your input!

But if a tube fails, would it be that much obvious? My concern is mostly about damaging the amp if a tube dies... 'Cause I don't have any spare fuse and I don't know if I'll be able to get one before the show.

 

[94Tremoverb]

Power tubes fail in three general ways - either they just stop working (least common) in which case you will certainly notice in a two-tube amp (you'll get a drastic loss of power and headroom, and bad tone) but possibly not much in a four-tube amp, unless it's really cranked - and this won't blow the fuse; or (fairly common) they become microphonic, which with power tubes is usually a rattling or rumbling noise that comes out through the speaker, and won't blow the fuse; or they short (most common), which *will* blow the fuse and you will certainly notice because the amp will stop working! So it really isn't much use to have spare tubes and not spare fuses - the chances are more than even that if you need one you'll need the other. They can also become physically rattly, which is annoying when playing quietly but isn't normally loud enough to be a problem at gig volume.

Preamp tubes generally fail in three ways too - but none of them blow fuses, so as long as you carry a spare preamp tube of each type the amp uses (or even just a 12AX7, which is pretty much usable temporarily in any preamp position even in those amps which are supposed to use others) you're covered. They either lose gain/sound bad, become microphonic, which with preamps is usually a whistling or 'ringing' feedback-type noise, or stop working altogether. All these about the same probability, and in all cases if you can't easily identify which tube it is from the channel or functions that are affected, or by tapping on the tubes to identify a microphonic one, simply change each in turn for the known good one until the problem stops.

If you're in an emergency situation at a gig, don't turn the amp fully off to change tubes - but you must put it onto standby. After you've put in a new tube, make certain the orange filament glow is visible before you flip the standby off - to check the tube is in its socket properly, as well as that it's warmed up. And make sure you carry some sort of glove, cloth or something to change power tubes... they get hot enough to burn your hands.

 

[nismofreakish]

The thing I forgot mentionning is that I might have to higher the volume since we're not gonna be miked this time. So I've been playing at the same volume level for years, do you think that may shorten my powertubes' life?

 

[thunda1216]

No. Carry a couple of spares, and some fuses and play. People have anxiety attacks over their tubes. Stop it. Play. Have some fun. You have a spare tire for your auto, right? Do you lose sleep worrying about flats? Play, Dammit!

 

[Shadow.Se7en]

I’m taking Thunda’s advice and playing dammit! But I’m also going to carry spares! :twisted:

I do have a question though, are all the tubes suppose to glow at the same intensity? I noticed that I have one that was glowing slightly less than the others. Is this common?

Thanks in advance!

 

[nismofreakish]

Thx guys!

For the different glowing tubes, mine have never shown the same light intensity and never had problem so far.

I went yesterday to buy a spare fuse for my single recto, I had printed the pdf back panel of the manual of my amp via the boogie website, but still, the guys asked me the length of the fuse since he had two, one about a inch long and the other half of it.

Since I'd like to go buy one before my rehease this afternoon, do you guys knows the exact length I need?

THX

 

[RussB]

Thx for your input!

But if a tube fails, would it be that much obvious? My concern is mostly about damaging the amp if a tube dies... 'Cause I don't have any spare fuse and I don't know if I'll be able to get one before the show.

Get some proper spare fuses, and take them with you to gigs along with a pair of power tubes. That's how I roll, YMMV and all that.

 

[RussB]

Thx guys!

For the different glowing tubes, mine have never shown the same light intensity and never had problem so far.

I went yesterday to buy a spare fuse for my single recto, I had printed the pdf back panel of the manual of my amp via the boogie website, but still, the guys asked me the length of the fuse since he had two, one about a inch long and the other half of it.

Since I'd like to go buy one before my rehease this afternoon, do you guys knows the exact length I need?

THX

Take the fuse from the amp with you...

 

[RussB]

If you're in an emergency situation at a gig, don't turn the amp fully off to change tubes - but you must put it onto standby. After you've put in a new tube, make certain the orange filament glow is visible before you flip the standby off - to check the tube is in its socket properly, as well as that it's warmed up. And make sure you carry some sort of glove, cloth or something to change power tubes... they get hot enough to burn your hands.

Good info, except for the bit about swapping tubes at a gig with the amp powered up. If you are skilled in aligning the tube's pins, then swapping the 12AX7's might be OK with the amp on "Standby" (might is the key word)

But please DO NOT try swapping power tubes with the amp on! Can you imagine what would happen if you managed to break the glass while removing or installing the tube? Death isn't worth the extra 60 seconds it takes to power down the amp.

 

[BostonRedSox]

If you're in an emergency situation at a gig, don't turn the amp fully off to change tubes - but you must put it onto standby. After you've put in a new tube, make certain the orange filament glow is visible before you flip the standby off - to check the tube is in its socket properly, as well as that it's warmed up. And make sure you carry some sort of glove, cloth or something to change power tubes... they get hot enough to burn your hands.

Good info, except for the bit about swapping tubes at a gig with the amp powered up. If you are skilled in aligning the tube's pins, then swapping the 12AX7's might be OK with the amp on "Standby" (might is the key word)

But please DO NOT try swapping power tubes with the amp on! Can you imagine what would happen if you managed to break the glass while removing or installing the tube? Death isn't worth the extra 60 seconds it takes to power down the amp.

Very true! A year ago I was swapping power tubes and one broke in my hands! I was even being pretty careful. Had I kept the amp on, yikes, my wife would've found me dead!

Don't mess around. Just turn the **** amp off and then go about swapping tubes. Patience in this case is more than a virtue -- it can be a matter of life or death!

 

[RussB]

Here's a pic from the bias mod thread...

 

[Shadow.Se7en]

Thx guys!

For the different glowing tubes, mine have never shown the same light intensity and never had problem so far.

THX

Although the one is slightly less in intensity, the amp seems to be working fine......so I guess no biggie!!

 

[94Tremoverb]

If you're in an emergency situation at a gig, don't turn the amp fully off to change tubes - but you must put it onto standby. After you've put in a new tube, make certain the orange filament glow is visible before you flip the standby off - to check the tube is in its socket properly, as well as that it's warmed up. And make sure you carry some sort of glove, cloth or something to change power tubes... they get hot enough to burn your hands.

Good info, except for the bit about swapping tubes at a gig with the amp powered up. If you are skilled in aligning the tube's pins, then swapping the 12AX7's might be OK with the amp on "Standby" (might is the key word)

But please DO NOT try swapping power tubes with the amp on! Can you imagine what would happen if you managed to break the glass while removing or installing the tube? Death isn't worth the extra 60 seconds it takes to power down the amp.

Not so. When the amp is on standby, the B+ (high voltage) is turned off. That's the whole point.

I would never have recommended doing this otherwise.

The filaments (6.3VAC) and the bias (~50VDC) remain on, but neither of these are enough to do you any harm.

There are *some* amps where this is not true - a lot of Peaveys, for example - but on all Mesas, the standby works this way. The only tubes that you must not change with the amp on standby are the rectifiers.

 

[KH Guitar Freak]

Pardon me, but I still don't get why you would change poweramp valves when the amp is turned on... :?

 

[fluff191]

Pardon me, but I still don't get why you would change poweramp valves when the amp is turned on... :?

+1

Preamp tubes sure. I do that all the time. But power tubes? That isn't a good habit to get into.

 

[94Tremoverb]

Pardon me, but I still don't get why you would change poweramp valves when the amp is turned on... :?

+1

Preamp tubes sure. I do that all the time. But power tubes? That isn't a good habit to get into.

Why not? If you understand what the standby switch does, you will know that it's just the same. There is no more risk from changing a power tube with the amp on standby than a preamp tube.

The reason for doing so is purely to save time backstage in an emergency situation. You will know immediately that you've got the new tube in the right way because the filament will light up without needing to flip the power switch.