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24.240.33.1
My first post to the Tubes Asylum. I replaced the two 6H30s in my ARC LS25mkII last May. Today, after perhaps 300 hours of running time since the install, I heard an erratic modulated low frequency rushing sound through both channels of my system that did not respond to preamp volume changes or input selection. It was clearly audible and distorted any program material from any source. All cables and connections checked out OK. I had a spare set of new 6H30s and swapped them in. Noise and distortion vanished. The system is now dead quiet and the sonics are fine. So, am I looking at just bad Electro Harmonics tube/tubes? (I did not swap them in, one at a time) Or is there something else that could be haywire in the electronics that caused premature tube failure and needs to be diagnosed? Thanks in advance.
Follow Ups:
I cleaned the pins on the "bad" tubes and the ARC's sockets with DeOxit per Jim's FAQ, and reinstalled them. Noise is gone, distortion is gone, and the overall sonics are great. Thank you Jim, for a valuable lesson. Let's hope the rehabilitated "bad" tubes are good for another 9,700 hours! And I still have the spare set of now tested and known-good 6H30s for future use.
I REALLY appreciate that nice post, and I'm glad the ARC is working well now!Sometimes I think people believe I post about tube/tube socket cleaning just to avoid responsibility for problems that people blame on tubes. I don't - but having your post makes it easier to believe the stuff in my FAQ post. I'm very grateful for the feedback you provided.
Best of luck with the ARC and its tubes!!
Edits: 08/16/17
Did you clean the sockets and retry?
I know that PITA type setup. That was one thing I was trying to "redo" when I redid my setup.
nt
I am FAR from an expert on tubes but I do know one thing. A lot of new gear really pushes those tubes HARD! This may be the case where you need a particular 6H30 that is more durable.
My Conrad Johnson preamp can only take two 6922s being it runs them hard. If I put a nice expensive vintage tube in there it will cook in a matter of weeks. that may be what's happening in your preamp. Much like my dreams of rolling in nice NOS tubes in my CJ will never happen, you may be in the same situation. A limited number of 6H30s to choose from.
Contact Jim McShane and see if what he says and if he has a more durable tube.
The choices for the 6H30 seem to be limited to 2 affordable versions: Sovtek and Electro Harmonix, each selling in the mid 30 buck range. The 6H30-DR super tube prices have shot through the clouds: 300 bucks or more. The usual quote for hours of life for the 6H30 in all of its flavors is 10,000 hours, far less that I achieved with the Electro Harmonix tubes. But, Jim (below) may be right about dirty contacts. I'm going to take his advice and post results in a day or two.
***The usual quote for hours of life for the 6H30 in all of its flavors is 10,000 hours***
This is perhaps the most meaningless and misunderstood number, that gets routinely thrown around without any idea of its true meaning. Just don't worry about it. The life of a good tube in a properly designed equipment is measured in many years, often in decades, not in some "hours".
I am certainly no tube expert - just quoting the standard doctrine about 10,000 hours. I will be very happy if my 6H30s last for decades. They will then be part of my estate, to be passed on to my heirs.
The tube lifetime in hours reflects its suitability to particular application, usually something other, than audio. In case of 6H30 tube it is its HUGE pulse currents that might become affected first. Does your preamp need 6A peak currents? Or will it be perfectly happy with "just" 5A?
So first of all you need to know the test conditions. Unfortunately, these are never disclosed, especially for the "special application" tubes like the 6H30. In most cases these conditions presume one or more parameters being at their maximum allowable level, or even above.
Second - you need to know the acceptance criteria. Usually it is one or more parameters beginning to fall outside the specified limits.
The truth is - those particular parameters might be of no significance for your application.
For REAL tube life other things have far more significance, than the "rated hours". Stress factor is one of them. Running the tube at 50% of its maximum stress will result in a far bigger longevity effect than selecting the tube model with a couple hundred more "rated hours".
The amount of time the unit is on/operating over any given period of time is not irrelevant however. For instance if you use your unit 2 hours a day on average that's 730 hours a year. But leaving it on all the time as some do will rack up 730 hours in just over 30 days. That WILL make a difference in the replacement interval of any tube, no question about it.
It is true that the number of off-on cycles can have some impact on tube life as well. Whether that can prolong tube life long enough to make up for 12 times (in my example) the numbers of hours the tube is in use is uncertain to say the least.
All else being equal - I don't agree at all that the number of hours of use is meaningless. It certainly is not the only factor affecting tube lifespan - but it is a factor.
You may not have had a tube problem - it may have been poor socket contact. Follow the link below to an FAQ post of mine for more info.
FWIW, I have had little to no trouble with the 6H30Pi-EBs I've sold.
I read your FAQ and will clean the pins and sockets and reinstall the "bad" tubes. It may take a couple of days before I post results, because moving the preamp out of its spot in the antique cabinet is a time consuming PITA - lots of inputs to disconnect in a tight spot with a flashlight and mirror. Sometimes moving a couple of components around makes me wish my gear was set up in an open rack with wheels.
Can you reinstall them one side at a time to test your theory? Regardless it sounds like a tube problem, and they should last much much longer. If you do a search of this asylum you will see discussions of that tube and the upgraded variant with the DR suffix. As I said read the old threads to catch up.
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