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Author Topic: Tube life... wich is better?  (Read 2447 times)
KE4JOY
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Posts: 1381




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« on: July 01, 2013, 02:45:42 PM »

Which is better for vacum tube lifespan... turn it on and leave it on (within reason) or turn it on for a short time and cut it off?

Opinions?  Grin
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K0IZ
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Posts: 737




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« Reply #1 on: July 01, 2013, 02:50:27 PM »

Somewhat is affected by filament circuit.  If inrush protection, turn on is not too much of a shock.  If no protection, the first couple of cycles can result in pretty high current to cold filament.  Also smaller filament transformers will deliver less high current surge.

That being said, my amp uses 3CX800's.  If I plan to use the amp within 3 or 4 hours, I will leave it on.  If longer, I mostly will turn off.
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KE3WD
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Posts: 5689




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« Reply #2 on: July 01, 2013, 05:23:16 PM »

Depends on the tube and the design of the circuit it is in. 

For most ham applications, turn it off when not in use and be happy.


73
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G3RZP
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Posts: 4731




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« Reply #3 on: July 02, 2013, 03:05:11 AM »

'WD,

And save the electricity bill!
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AD4U
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Posts: 2173




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« Reply #4 on: July 02, 2013, 06:41:54 AM »

If you are talking about tube type receivers and transmitters from the boat anchor era, my vote is to turn them off if they will not be used for a couple of hours.  Us old timers who used vacuum tube rigs when that was all that was available can attest that vacuum tubes were not problematic often lasted MANY years. 

For example: I bought a Drake R4C and T4XC brand new in 1974.  This was the only rig I had until 1985.  They saw a LOT of use in those 11 years.  I still have them and they are still used occassionally.  In the 39 years since I bought these rigs, I have only had to replace one tube and that was in the receiver.

Dick  AD4U
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K8AXW
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« Reply #5 on: July 02, 2013, 09:44:16 AM »

4U:  Amen!  My 30+ year old TS-830S is still using the original tubes!  I thought I had a problem with the driver tube recently and pulled the driver and both 6146s..... tested them on my old Hickok tube tester.....great shape.  Found the problem was something else.  Rig putting out full load once again.

My HB linear with 2 Eimac 3-500Zs..... 30 years old and still cranking out full load.....

When no being used, turn 'em off. 
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G3RZP
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« Reply #6 on: July 02, 2013, 01:21:38 PM »

I still have a pair of Sylvania 6L6G that my father paid the equivalent (then - in 1937!) for then of 50 cents each. They are still good.....

They're probably older than many of the posters here.....
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W8AAZ
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Posts: 350




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« Reply #7 on: July 07, 2013, 04:37:40 PM »

Restoring old broadcast radios, you may find receivers with the original tubes installed from back in the day. They were probably turned on and off alot, and have many hours of use.  Alot of old radios that saw years of use still have the original tubes and they are working fine.  Or have maybe a couple or 3 of the original tubes and maybe one or two replacements.  That shows that they apparently do not all age at the same rates.  Almost a random thing.  Maybe one tube croaked in a couple years or more after the set was bought, and the rest soldiered on for decades. Transmitting tubes are a different matter. I would say how hard they are driven and other factors are just as much an effect as how much they are turned on and off. Some data that shows tx tubes run at or just a little below their rated filiment voltages last longer, if you have some way to adjust that and monitor it. As it would be easy to get a bit of extra fil. voltage depending on line variations.
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AC5UP
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« Reply #8 on: July 07, 2013, 08:31:29 PM »

That shows that they apparently do not all age at the same rates.  Almost a random thing.

Not random at all as the life of a tube is affected by usage (on / off cycling), circuit design, and the load it works with.

The next time you have your hands on an all-glass Five Tube All America take a peek through the back cover as you turn it on. Not unusual for one of the tubes to light up faster & hotter, then drop to a lesser glow as the other tubes come up to temperature. That tube will be more prone to a blown heater than the rest but it is possible another tube will go weak (low emissions) before that happens. Change the weak tube and the dynamics of the filament string could change enough to delay the filament failure even further. In a transformer operated radio the tubes most likely to fail usually run the hottest. Rectifier and audio output typically, but low power IF amplifiers like a 6AU6 tend to last almost forever. I have never found a bad 6H6 or 6AL5. That's a dual diode detector (same tube with the 6H6 an 8-pin Octal and the 6AL5 a 7 pin Novar) and operate under almost no load or power dissipation. Which makes a huge difference as they run very cool and have small heaters.

In TV's from the day the tube most likely to fail was the horizontal output. Usually the largest and hottest tube in the set except for the CRT (largest) which tended to be the last tube to fail... And that's a bit of a play on words because a CRT replacement was expensive enough that junking the set usually made more sense. So when the CRT failed that would tend to be " the-last-tube-to-fail ". Why replace the highest dollar part in a set with 10 years on the clock when a new TV with all-new parts and warranty was within a hundred bucks or so?

Which explains why you're more likely to find a Fabulous 50's radio than a TV from the same era.............. The radio could be kept in repair far longer and for less money than the TV.

BTW: Here's a related trivia item: What was the best selling American car in 1957? It was the Ford Fairlane. Which is the most restored car from 1957 and probably the most collected car of all time? That's the 1957 Chevrolet Belair.

Why ?
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KC4MOP
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Posts: 743




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« Reply #9 on: July 08, 2013, 04:23:51 AM »

My R390A does not like Summer time, as I turn it off for short periods of time. A couple of weeks, here and there. Much less time in the shack during the Summer months. It seems like it needs to get the heat back into it's veins before it is totally happy and stable. It loves 24/7 operation. I have an old TV type tube caddy loaded with many tubes, for the table top TX's and my 390A. Antique Electronic Supply in AZ still selling tubes. I do not get flustered over the prices. It may be 2-3 years for any maintenance issues. It is powered by an old TV isolation transformer set for 115 vac. It is not being hit with today's 130 vac electric.
The table top transmitters can be turned on when needed. The consumer type tube receivers should also be turned off when not in use. The military gear was designed for 24/7 use.
« Last Edit: July 08, 2013, 04:28:59 AM by KC4MOP » Logged
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