Looking for tube reliability input

[heisthl]

Anyone playing a tube amp professionally should always have an extra set of tubes with them & know how to deal with it. They just go bad. Odd that it showed up in the PI & not a gain stage. I will sure be glad when some of the new 12ax7s wind up bullet proof.

No time to troubleshoot during a show - you just have to swap out the amp. Ditto on bullet proof 12AX7s

[Smoothfingers]

I am seeking input from this forum regarding tube relability. Specifically, Mesa Boogie's recommendation to replace their premium tubes every two years. This guidance is quite unusual to me. I own several vintage amplifiers with RCA tubes dating back to the 1960s—specifically, four amplifiers housing approximately 36 tubes—that continue to function reliably after six decades. I am curious as to when it became standard practice for tubes to have a service life of only two years.

This inquiry is prompted by my experience with my 1983 S.O.B amplifier. In 2019, I replaced its 6L6GC power tubes with units purchased from Mesa Boogie. The amplifier has remained stationary in my studio for seven years and accumulated fewer than 500 hours on these new tubes; nevertheless, one recently failed. Upon contacting Mesa Boogie, I spoke with Kris Dilbeck to discuss this matter. I did not request reimbursement or credit, given the passage of time, but questioned the rationale for repurchasing their tubes. When I specifically asked Kris about this, he reiterated the company's position to replace tubes every two years.

As an amp technician and a recording and performing artist with five decades of experience, I consistently ensure all amplifiers are biased within proper dissipation specifications. Additionally, I play jazz at modest volumes and do not use distortion. Given these circumstances, I would appreciate any insights or reasons from the forum as to why I should consider purchasing another Mesa Boogie tube, based on my experiences.

[nuke]

I think you got Mesa's "business answer" which is to relieve themselves of any financial responsibility for anything, ASAP. That's why they recommend 2 years. That and they can stimulate sales of replacement tubes.

We have to remember, vacuum tubes are no longer mass produced and subject to the scrutiny that happened when millions upon millions of electronic appliances sold to everyone from consumers, to industry, to aviation, to government and military and space exploration.

Back before 1975, *millions* of tubes were sold in millions of TV sets every year, by the likes of RCA, Zenith, Motorola, Sylvania and others. They enforced a lot of quality checks on tubes and all other components used in those products.

Then there was the military and space programs and the nuclear arsenal. They also ran on tubes. If you want a hint at that, then look at the history of the Bendix Red Bank tubes.

For some critical applications, vacuum tubes were subject to individual testing including shock and acceleration. Other applications would include the tests during qualification and sampling in production. You can find the industrial and military type equivalents for tubes of interest and see how they were tested.

in reality, the expectation for most signal-level receiving tubes was a 10,000 hour useful life and 5000 hours for most power tubes. But of course, they used them well within their data sheet numbers to increase the life of the tubes and reduce service intervals for equipment. It is not unusual to find commercial audio equipment that was built in the 50's and 60's, with completely functional tubes in them, even today. You know they were used every day for decades.

[martin manning]

I am seeking input from this forum regarding tube relability. Specifically, Mesa Boogie's recommendation to replace their premium tubes every two years. This guidance is quite unusual to me. I own several vintage amplifiers with RCA tubes dating back to the 1960s—specifically, four amplifiers housing approximately 36 tubes—that continue to function reliably after six decades. I am curious as to when it became standard practice for tubes to have a service life of only two years. ...
I would appreciate any insights or reasons from the forum as to why I should consider purchasing another Mesa Boogie tube, based on my experiences.

Replacing tubes every two years is not a good recommendation, it's just something that is measurable and provides an out for any liability. Hours of operation would be a better yardstick, but few people track that with any accuracy, and the actual operating conditions are beyond their control. They are not the manufacturer, but they may have some role in selection, either through in-house testing or by some agreement with the manufacturer. If you buy your tubes elsewhere, you may or may not have better visibility into the selection criteria.

Tubes can fail at any time, but they will most definitely last longer if the heater voltage and plate dissipation are within spec. "Getting the Most out of Vacuum Tubes," available on-line here: http://www.tubebooks.org/Books/Atwood/T ... 0Tubes.pdf, is the only resource I am aware of that discusses tube failure in any detail.

[xtian]

Mesa also typically DOES NOT PROVIDE BIAS ADJUSTMENT in their amps, another attempt to lock owners into buying MESA branded and graded tubes. Adding a bias adjustment pot and keeping your power tubes cool is a good investment, and then you can use whichever tubes you want.