How long do tubes last ?

[jnewmark]

Did'nt really see this in the Amps FAQ ( the subject, printed in blue, means it is being edited ), so I wonder if we could get some views. I recently mentioned in the Portaflex thread that I was going to replace the tubes in my '67 B15N, and got some discussion going about why I was even considering it, to the difference in some brands of tubes for the same model. But what I'm really wondering is, how long do tubes in a bass amp usually last, and how do you know when to change them? Should they be changed as a set, or individually as needed? I was told that some guys have tubes in their amps that are 40 years old, and don't see the need to get new ones, or NOS tubes. My guitar player ( Fender Super Reverb ), changes them every 5 years or so. So, what do you think about the life of tubes, when should they be switched out for new, or NOS models, or, are they good until they finally die? What about new as opposed to used, or NOS tubes? Anything else you want to add, feel free.

[korchm]

its just the power tubes that goes bad after a while. IME about every 3-5 years of moderate playing time. Preamp tubes on the other hand lasts forever..unless they break physically or you decide to change them.

[michael_atw]

I bought a '69 Ampeg B25 last summer. It still has tubes that may be 40+ years old in it. As far as I'm concerned, they sound great and need no changing.

I figure, it depends on how much it is used and how it is used. It reminds me of a battery for a computer or Ipod. If one doesn't charge the battery correctly, it wears down faster. However, if one takes care of the battery correctly it may last for far longer than Apple hoped it would.

[liltommyg]

The tube decay is pretty much down to use- a lot of use = heat & will degrade the tubes.

[jokerjkny]

preamp tubes are one thing, but for power amp tubes, it depends on how hot they've been biased in the amp. some prefer a hotter bias resulting in a growlier, quick to overdrive, sizzly tone, but this can also quickly shorten the life of any power amp tube.

[rdwoody1]

When its time to change tubes, you'll just know it. Your amp will start suffering from odd noises or obvious loss of power/volume. You can check preamp tubes by tapping them with a non-metal object with the amp on. I usually use a pencil. If you can hear the tapping coming through the speakers pretty loudly, you've got a microphonic preamp tube and you can just swap another in. Power tubes are not that easy, they generally don't just go microphonic and can't be checked the same way. Also, power tubes can't just be individually switched out. They are sold in matched pairs that are tested to work together, and most of the time, if you're going to change a power tube, you need to go ahead and do a full power section swap. As far as life goes, amount of use plus treatment are the big factors. It is a good idea to let the tubes cool off before moving the amp, they are more prone to damage while warm.

[Walking]

Back in the day we had tube testers which would indicate if a tube was running out of spec. IMHO, its pretty hard to tell nowdays--maybe if you have a way of measuring the tube current and comparing it to bias. One thing is to look for discoloration of the silver 'getter' sprayed on the inside of the tube which captures air molecules to maintain the vacuum.

The only obvious, besides simply a blown tube, is when they become microphonic.

[B-string]

In a well designed, properly running amp, output tubes can last a very long time. 10 years to ??. Average life that I've seen in 40 + years, 25 to 30 years, not convinced that they were even replaced due to being "bad". Ampegs, Fenders, Marshalls, Sunns,Vox..... Just like ANY electronic componet they can fail without any warning or notice or unlike a light bulb can give you warnings.

[JimmyM]

j, how dare you question your portaflex club president!!!



so please ask your guitarist if i can have his old tubes since i also have a super reverb. great amp, btw. amazingly good for recording mic'ed bass as well, i've come to discover.

anyway, yes, the best rule of thumb (and certainly the cheapest) is if it ain't broke, don't fix it.

[T-Bird]

Hi.

From a second to infinity.

Well perhaps not infinity, but still longer than an average musicians lifetime .

Like said previously, after the initial "burn in" period, the use and how it's used determines the life-span of a tube.

For CP quality tubes, I'd say about 2 years with 1 rehearsal, 1 show a week.

Regards
Sam

[jnewmark]

Originally Posted by JimmyM

j, how dare you question your portaflex club president!!!



so please ask your guitarist if i can have his old tubes since i also have a super reverb. great amp, btw. amazingly good for recording mic'ed bass as well, i've come to discover.

anyway, yes, the best rule of thumb (and certainly the cheapest) is if it ain't broke, don't fix it.

Ha Ha, sorry Jimmy, you are the TUBE GURU as far as I am concerned! Just thought I would get a separate thread going on the subject instead of sidetracking the Portaflex thread. I really know nothing about switching out tubes and setting the bias, etc., especially since my portaflex has no bias control on the back ! Just thought that, after the main cap on my B15N blew last week, the tubes were probably going to be next. I almost have a complete set now for spares, so I'm prepared, although this bias thing worries me now ! RE: the Super Reverb, he bought a new one about 10 years ago and has been blowing tubes in it ever since. he finally went back to the old '70's one he's had and has'nt had a problem with it yet !

[JimmyM]

oh please, j! i am no tube guru at all. thanks that you think so, but the only thing i know about tubes is how not to get ripped off by buying into this "change your tubes regularly" nonsense.

[jnewmark]

Originally Posted by JimmyM

oh please, j! i am no tube guru at all. thanks that you think so, but the only thing i know about tubes is how not to get ripped off by buying into this "change your tubes regularly" nonsense.

Maybe so, but I still look to you for all things concerning Ampeg Portaflex ! BTW, I looked at my tubes this morning for the first time since I got my B15 about two years ago, and saw a mismatch of tubes in there: one power tube is larger than the other and is a Tung Sol, the other is the "Ampeg " Sylvania. The three Sl7's are Ampeg Sylvanias, two of them have a 739 number, the other one a 726. The 5ar4 is a no-name, as far as I can tell. The amp sounds fine to me, but , obviously the tubes are not a matched set.

[JimmyM]

not necessarily. i mean it's kind of unlikely they're matched, but they could still test as matching. still, it is better feng shui if they're the same brand and size

[Goodlawdy]

I'm dealing with the power tube situation right now. I have an intermittent noise happening (about 2 seconds, once a practice) where my VB-2 makes a high pitched sound. Peavey told me it was a power tube on its way out. I can't tell which one. None are glowing brighter or have a discoloration. There are six, so a retube ain't cheap!

I just know the one festival gig we have this summer will be the time when the noise happens and won't stop. I don't want to sell it. Guess I'm going to have to bite the bullet, or take it to be serviced.

Originally Posted by rdwoody1

When its time to change tubes, you'll just know it. Your amp will start suffering from odd noises or obvious loss of power/volume. You can check preamp tubes by tapping them with a non-metal object with the amp on. I usually use a pencil. If you can hear the tapping coming through the speakers pretty loudly, you've got a microphonic preamp tube and you can just swap another in. Power tubes are not that easy, they generally don't just go microphonic and can't be checked the same way. Also, power tubes can't just be individually switched out. They are sold in matched pairs that are tested to work together, and most of the time, if you're going to change a power tube, you need to go ahead and do a full power section swap. As far as life goes, amount of use plus treatment are the big factors. It is a good idea to let the tubes cool off before moving the amp, they are more prone to damage while warm.

[jnewmark]

Originally Posted by JimmyM

not necessarily. i mean it's kind of unlikely they're matched, but they could still test as matching. still, it is better feng shui if they're the same brand and size

What exactly do you mean by " matched " anyway? Is it that they test the same strength ?

[Bassmec]

Well it means that for a given level of grid bias the same quiescent current may be passed from anode to cathode by a tube that is matched.
News Flash!!! "Tubes should be changed at least as often as your underwear"
Quote: Chairman of global tube retailers, Cryogenic Resources Association Producers.

C.R.A.P.
Nah mate! if you have a new old stock quality set, matched and biased for 75% of total emission power tubes, we might expect have >25 years of daily use out of them.
But thats the old vacuum electron tube, now we have progressed to the all newly designed partial vacuum tubes that turn white and milky after a month and fail in only a few months, this is progress chaps no longer a need to just fill your amp with reliable tubes and confidently use it, No, no its the all new accountancy lead engineering way forward chaps!.

[B-string]

Originally Posted by jnewmark

{snip} RE: the Super Reverb, he bought a new one about 10 years ago and has been blowing tubes in it ever since. he finally went back to the old '70's one he's had and has'nt had a problem with it yet !

His previous amp is an example of an amp that has a problem, not the fault of the tubes. If your Portaflex is original it is probably "self-bias" no adjustment required.

Originally Posted by Goodlawdy

I'm dealing with the power tube situation right now. I have an intermittent noise happening (about 2 seconds, once a practice) where my VB-2 makes a high pitched sound. Peavey told me it was a power tube on its way out. I can't tell which one. None are glowing brighter or have a discoloration. There are six, so a retube ain't cheap!

I just know the one festival gig we have this summer will be the time when the noise happens and won't stop. I don't want to sell it. Guess I'm going to have to bite the bullet, or take it to be serviced.

Cold solder joints, leaky signal caps and poor wire dress can cause this as well as a preamp tube. Have it checked out and provide a complete discription of the trouble as well as how long and how you are using it. May not be output tubes at all.

[stiles72]

As a rule of thumb, I wouldnt replace a tube unless something wrong with it or unless you want to experiment with a different sound. There's nothing wrong with a tube just because it old. In fact, odds are - the older tubes are probably better built.

When I bouth my Portaflex, it had a modern set of JJ's for power tubes and a hodgepodge of brands for the preamp tubes. Just for kicks, I scrounged Ebay and other places looking for Ampeg Branded Sylvanias like what would have been stock in the amp. I eventually found some, and I swapped them out. Even though they are all "old tubes" and certainly weren't NOS, they sound excellent.

[akaTRENT]

To put it simply, once it sounds bad is when its time to change the tubes, though thats different for every person.