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Author Topic: 572b Reasonable Life Expectancy  (Read 2369 times)
N4JTE
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« on: January 25, 2013, 04:08:44 PM »

I use an 811h amp with the W8JI, 572b conversion. My usual time on air with amp on is 3 to 4 hours a day almost every day.
How many hours can one expect before the tubes will show some deteriation in output or other type problems?
Bob
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KE3WD
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« Reply #1 on: January 25, 2013, 04:12:29 PM »

Nobody can give you an answer that will be meaningful. 

For one thing, you don't even bother to identify the manufacturer of your tube. 

73
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W8JX
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« Reply #2 on: January 25, 2013, 05:09:54 PM »

I use an 811h amp with the W8JI, 572b conversion. My usual time on air with amp on is 3 to 4 hours a day almost every day.
How many hours can one expect before the tubes will show some deteriation in output or other type problems?
Bob
 

Most likely the tube will fail from gas in tubes before you "wear" them out. A 811H amp lacks the power supply to properly utilize 572b's and the result is the plates/anodes may never get warm enough to properly getter. This is important because modern Chinese tubes tend to leak a bit more and than older counter parts. The 811 and 811H use same power supply. In a 3 tube version there is the ability to run them a bit harder than normal 811 levels to heat plates more but no reserve left on 4 tube model.
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K0ZN
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« Reply #3 on: January 25, 2013, 05:51:36 PM »

Extremely difficult to quantify. There are just too many variables, including quality of manufacture, tuning techniques, operator errors, even extraneous stuff like lightning hits in your area. IF you are careful in how you tune up, reasonably conservative in operation, and you are lucky enough to not have a tube seal failure, they likely will last years....maybe.... or one tube may die in two weeks and others last much longer.

73
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N4JTE
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« Reply #4 on: January 26, 2013, 04:52:56 PM »

Okay tnx.
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AD4U
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« Reply #5 on: January 26, 2013, 06:14:04 PM »

My Heathkit SB-200 is still running the original Cetron 572B's after 41 years.  They still give 600 watts out.

Dick  AD4U
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N9AOP
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« Reply #6 on: January 27, 2013, 01:32:12 PM »

Hard to say.  I have an 811H with 572b's that runs about 2hrs a day and the tubes will be 10 years old in April.
Art
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N6AJR
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« Reply #7 on: January 27, 2013, 02:32:34 PM »

With a bit of luck you could have the tubes out last you !!!  don't push them too hard,  give a little time for warm up and cool down, get the dust out of the amp now and then, and they could go for a long time, or one of them could have a defect and blow tomorrow, reguardless of hou you treat them. ut using them every day is actually good for them.
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W8JX
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« Reply #8 on: January 27, 2013, 02:46:10 PM »

don't push them too hard,  give a little time for warm up and cool down

It is not really possible in a 811 amp and tubes are basically instant on and only need a few seconds.   
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G4FUT
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« Reply #9 on: January 27, 2013, 02:58:39 PM »

Mt Heathkit with 572bs lasted from new for about 35 years.  What gave out first was a smoothing capacitor in the PA stages.
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N2CJ
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« Reply #10 on: January 27, 2013, 05:44:18 PM »

My Heathkit SB-200 is still running the original Cetron 572B's after 41 years.  They still give 600 watts out.

Dick  AD4U

Mine too. I think they are a little soft on ten meters, though.
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G3RZP
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« Reply #11 on: January 29, 2013, 03:30:42 AM »

There's a lot of difference between Cetron and Chinese. I'd rather have Cetron myself.
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