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PostPosted: Apr Sat 07, 2007 3:34 am 
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The design life of most receiving-sized tubes is between 5000 and 7500 hours. In addition, there are several dozen "10000" hour types that have THAT stated design life.

Of course, the actual life varies considerably with the application.

Regarding RCA's special red tubes..... When RCA introduced the 5692, their 10000 hour 6SN7GT, they solicited Federal Telephone, who used 6SN7GTs in their repeaters. Federal replied that they saw no reason to spen 2.5 times the price of a regular 6SN7GT, since they were getting 70000 to 80000 hours out of regular 6SN7GTs. You see, repeater service is a very gentle service.

Regarding ENIAC (and other tube computers).... Those that used 6SN7GTs had incredibly high failure rates and tube lives as short as two weeks. This was due to the fact that some of the tubes were rarely "used" by the computer, and when they were held in the cutoff condition for long periods of time, they developed a cathode poisening referred to as "sleeping sickness". This was, essentially, the formation of a resistive layer between the cathode sleeve and the coating. "Computer Rated" tubes like, for example, the 5963, are tubes with special cathodes designed to thawrt that problem.

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PostPosted: Apr Sat 07, 2007 4:56 am 
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Leigh wrote:
HuggyBear wrote:
Leigh - are you sure about those tube numbers?
5690 - double rectifier
5691 - heavy duty 6SL7
5692 - heavy duty 6SN7
5693 - metal pentode

Hi Huggy,

Image

The 5690 is a dual rectifier similar to a 5U4, but not exactly like any commercial part. It came out after the other three, so is not mentioned in this brochure.

I have all four types in my collection.


Impressive! I learn something new everyday.

The 5690 is so unique it has a special basing - the 5690 base. It is a dual rectifier, literally - two completely separate diodes with completely separate heaters. I'll have to keep an eye out for them.

Just checked Tubes & More...the red base tubes are expen$ive! 5692 is almost $75.

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PostPosted: Apr Wed 11, 2007 7:55 pm 
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Having some "modern" tube audio equipment, vacuum tube longevity is one of my main concerns, so I have asked several manufacturer's their opinions.

The general concensus is that the power tubes last around 3000 hours (range of 1000 to 5000 hours), and the less demanded tubes last around 10,000 hours. But I just read somewhere about a commercial transmitting tube that ran for 70,000 hours, and was only taken out of service to become a spare!

Try reading "Getting the Most Out of Vacuum Tubes" by Tomer. Informative reading.


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PostPosted: Apr Thu 12, 2007 3:43 am 
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Mullard offered a series of 10,000 hour tubes called "10M". The 5693 is equivalent to the 6SJ7. Have a pair in my Scott 800B as limiters.
Found a 5692 in my CTC-4 as horiz. osc and control. Checked ok, so I left it in.
A good book on the subject is "Getting The Most Out of Vacuum Tubes" by Robert B. Tomer, which was re-printed by Audio Amateur Press, Peterborough, NH in 2000. The original was published by Sams in July 1960.
Kevin

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PostPosted: Apr Thu 12, 2007 4:19 pm 
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I know of one Zenith AM-FM set from around 1960 or so that's been playing 8 hours a day, 40 hours a week for the last 20 years. If my math is correct that's over 40,000 hours of playing time. Before I gave the set to one of the secretaries at work I cleaned the controls and noticed it had all the original tubes in it....still does. I usually got 5 years of service out of the final tubes in the transmitters, we used a pair of 8877's running at half their ratings in intermittent 2 way radio service. Running them this conservatively the most common failure mode was filament failure or internal arcing.


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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Mon 13, 2020 5:02 pm 
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This is a 12 year old old post, but the question was not answered with any truth.
Small signal tubes (not battery type direct filament) last at least 25K hours when operated within manufactures specs. Power audio tubes last less hours use vs small signal tubes. It is well known TV sweep tubes (like audio power tubes but with a high current oversized filament) were operated 16 hours a day for 10 years everyday. That is 58K hours.


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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Mon 13, 2020 11:14 pm 
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Nope. As a professional TV technician, my experience was that the sweep tubes in color TV's like 6JE6 and 6JS6 were doing really well to last a year in daily use. I've probably replaced literally thousands of them. You could count on replacing them on nearly every service call because they had extremely high failure rates. Improved versions like the 6LQ6 were not much better.

The other really horrible color TV tube was the 6GH8 which some sets had 7 of and all 7 of them were likely to be bad (weak, leaky, interelement shorts) at the same time. In fact RCA production 6GH8's were so poor that RCA used a Sylvania 6GH8 in the 3.58MHz osc position as OEM in many of their sets in an attempt to get better life from it.

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 12:29 am 
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Mr. Detrola wrote:
Nope. As a professional TV technician, my experience was that the sweep tubes in color TV's like 6JE6 and 6JS6 were doing really well to last a year in daily use. I've probably replaced literally thousands of them. You could count on replacing them on nearly every service call because they had extremely high failure rates. Improved versions like the 6LQ6 were not much better.

The other really horrible color TV tube was the 6GH8 which some sets had 7 of and all 7 of them were likely to be bad (weak, leaky, interelement shorts) at the same time. In fact RCA production 6GH8's were so poor that RCA used a Sylvania 6GH8 in the 3.58MHz osc position as OEM in many of their sets in an attempt to get better life from it.

Tube TV BW 10 years no service. On all the time. TV repair person at everyone house once per year? Not.


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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 12:48 am 
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Having worked in the industry in a number of different shops since the early 60's, that seemed to be the average on service calls. Once a year. Color sets required service more often than the black and white sets, but not that much different than most brands of black and white sets. The exception was Zenith black and white sets, if you had one of those it might go a few years between service calls. They were indeed built better than the competition and had a better picture as well.

Eventually most people would carry their black and white sets into the shop, except for senior citizens, to save the cost of a home service call, and those who were handy would test their own tubes and replace them without having to get someone to service the black and white set. Very few people tried to service their own color sets.

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 1:26 am 
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When I was little we had one of the BW Zenith jobs with the metal case, not a console. I guess it was reliable and even survived a lightning hit to play again I have been told. I can remember seeing some kind of Mercury launch on it when I was little but I don't know which one it was. My folks had a thing for Zenith electronics which apparently was a good decision. All they got left is the 1964ish console stereo that I repaired in the last couple years. The old caps were pretty much good, it was the transistors that were failing.

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 3:41 am 
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My Philco B569 after re-cap and new 100ma. tubes ran 24/7 for over 5 years
until I got bored with it. Still worked as good or better than it started.

Rob

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 5:42 am 
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Usually 24/7 operation is easier than cycling. Heating and cooling stresses the glass-to-metal seals and the filament material.

Rich


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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 2:49 pm 
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I have a warehouse full of equipment that emphatically states "tubes can last over 70 years ;-). Isn't that the TRUE life determination?

I'd also imagine that a lot of this gear WAS operated continuously, or nearly so.... although that is just a guess of course.

Heat is a tube killer ... more than hours, from my experience. Probably why the higher power tubes fail sooner in most cases. Of course there were those design blunders where a given tube by a given manufacturer was just a dud until replaced by an "upgraded" version.

Bottom line in my book... there is no such thing as tube life expressed in hours, in the real world.

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 3:52 pm 
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Mr. Detrola wrote:
Nope. As a professional TV technician, ...

The other really horrible color TV tube was the 6GH8 which some sets had 7 of and all 7 of them were likely to be bad (weak, leaky, interelement shorts) at the same time. In fact RCA production 6GH8's were so poor that RCA used a Sylvania 6GH8 in the 3.58MHz osc position as OEM in many of their sets in an attempt to get better life from it.


Agreed. I have three sleeves of "RCA" branded 6GH8 tubes that are manufactured by Sylvania (Obvious by the font and "ink" used to label the tubes.) Somewhere, I took a picture of these tubes to illustrate that but (as usual) can't put my finger on it at this minute. However, I think you understand...

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 6:45 pm 
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Don Cavey wrote:
Mr. Detrola wrote:
Nope. As a professional TV technician, ...

The other really horrible color TV tube was the 6GH8 which some sets had 7 of and all 7 of them were likely to be bad (weak, leaky, interelement shorts) at the same time. In fact RCA production 6GH8's were so poor that RCA used a Sylvania 6GH8 in the 3.58MHz osc position as OEM in many of their sets in an attempt to get better life from it.


Agreed. I have three sleeves of "RCA" branded 6GH8 tubes that are manufactured by Sylvania (Obvious by the font and "ink" used to label the tubes.) Somewhere, I took a picture of these tubes to illustrate that but (as usual) can't put my finger on it at this minute. However, I think you understand...

Japanize made quality 6GH8. Raytheon imported a lot of Japanize tubes in the 1960s.


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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Tue 14, 2020 9:41 pm 
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jimbenedict wrote:
...
Japanize made quality 6GH8. Raytheon imported a lot of Japanize tubes in the 1960s.


I would agree also that the tubes made in Japan seem to be top notch also. I have several 7591 tubes made by Toshiba and some by Hitachi.

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Wed 15, 2020 1:17 am 
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I was in the TV repair business for five years. We did not get called back to replace the same tubes for the same customers every year. Not even sweep tubes. Three to five years was typical for customers who used their TVs for several hours a day. For bedroom and spare room TVs that saw less use, it was not unusual to get 10-15 year old sets which still had the same tubes they left the factory with. Of course the reason they came to the shop was typically because two or three of those tubes were finally ready for replacement!

The problem with trying to quantify tube life is there are simply too many variables to pin it down to a simple number or set of numbers. Exactly how a tube is operated in a piece of equipment makes a tremendous difference. Voltages, currents, waveforms, and frequencies all have an impact, as does bulb temperature, vibration, heating and cooling cycles, and other factors. We saw situations where tubes would last a couple thousand hours in some TVs before they would weaken, but easily last two or three times as long in other brands of TVs. Or among TVs of the same make and model, the the tube in the low level sync separator/AGC circuit would last forever, but the three tubes of the same type in the color demodulator circuit would always be weak and failing if they were more than a few years old.

Another problem is, how do you quantify end of life for a tube? When it fails so completely and catastrophically that it cannot be used in anything any more? When it gets weak enough that it doesn't work in one circuit but may still work in some others? Under low or high line voltage conditions? Add to that the fact that tubes are manufactured products which are subject to normal variations in processing and fabrication, so they will not all last the same length of time even if operated under identical conditions. Then on top of that, not all tubes were created with equal lives to begin with. The hairpin 50-mA filament in a battery portable tube simply does not have the surface area for more than a tiny bit of emissive coating material. So its life expectancy will be shorter by an order of magnitude or more compared to bigger tubes with larger cathode sleeves.

About the best one can do is take averages of large numbers of tubes of a given type, but averages are averages, not ratings or specifications. They cannot be used to predict how long any particular tube will last even if all the factors involved can be accounted for.

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Wed 15, 2020 2:01 am 
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Chris108 wrote:
I was in the TV repair business for five years. We did not get called back to replace the same tubes for the same customers every year. Not even sweep tubes. Three to five years was typical for customers who used their TVs for several hours a day. For bedroom and spare room TVs that saw less use, it was not unusual to get 10-15 year old sets which still had the same tubes they left the factory with. Of course the reason they came to the shop was typically because two or three of those tubes were finally ready for replacement!

The problem with trying to quantify tube life is there are simply too many variables to pin it down to a simple number or set of numbers. Exactly how a tube is operated in a piece of equipment makes a tremendous difference. Voltages, currents, waveforms, and frequencies all have an impact, as does bulb temperature, vibration, heating and cooling cycles, and other factors. We saw situations where tubes would last a couple thousand hours in some TVs before they would weaken, but easily last two or three times as long in other brands of TVs. Or among TVs of the same make and model, the the tube in the low level sync separator/AGC circuit would last forever, but the three tubes of the same type in the color demodulator circuit would always be weak and failing if they were more than a few years old.

Another problem is, how do you quantify end of life for a tube? When it fails so completely and catastrophically that it cannot be used in anything any more? When it gets weak enough that it doesn't work in one circuit but may still work in some others? Under low or high line voltage conditions? Add to that the fact that tubes are manufactured products which are subject to normal variations in processing and fabrication, so they will not all last the same length of time even if operated under identical conditions. Then on top of that, not all tubes were created with equal lives to begin with. The hairpin 50-mA filament in a battery portable tube simply does not have the surface area for more than a tiny bit of emissive coating material. So its life expectancy will be shorter by an order of magnitude or more compared to bigger tubes with larger cathode sleeves.

About the best one can do is take averages of large numbers of tubes of a given type, but averages are averages, not ratings or specifications. They cannot be used to predict how long any particular tube will last even if all the factors involved can be accounted for.

Thanks for truth about TV service intervals and others just did not remember correctly. Most tubes lasts way longer than manufactures stated too. I read 1.5 volt 50ma filament battery radio tubes may only last 1000 hours.


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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Wed 15, 2020 3:16 am 
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Hmm. I would say an ideal testing ground would be maybe industrial test equipment, where high quality parts and design are prominant. Like old scopes and signal gens etc. that were on in labs all day 5 or 6 days a week. Like someone could recall how many months or years Tek scopes would play in the lab without needing tube replacement. Or even, in the old early vacuum tube computers. I bet that was an application where tube life was of interest! And maybe documented.

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 Post subject: Re: Average life of vacuum tube in hours?
PostPosted: Jan Wed 15, 2020 4:48 am 
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wazz wrote:
Hmm. I would say an ideal testing ground would be maybe industrial test equipment, where high quality parts and design are prominant. Like old scopes and signal gens etc. that were on in labs all day 5 or 6 days a week. Like someone could recall how many months or years Tek scopes would play in the lab without needing tube replacement. Or even, in the old early vacuum tube computers. I bet that was an application where tube life was of interest! And maybe documented.

Owners of FM police tube scanners are very good info. These ran 24 hours a day for years.


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