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Old 2nd March 2007, 07:08 PM   #1
Salas is online now Salas  Greece
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Default KT88 Lifetime estimation

Can you roughly estimate the healthy lifespan of an EH KT88 run on 15W plate, 6V (0.3V less due to drop) heater?
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Old 2nd March 2007, 08:07 PM   #2
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Your likely to be limited by the oxide cathode to a few thousand hours at best.
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Old 2nd March 2007, 08:17 PM   #3
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Thanks, circa 4-5 khours with such a low taxation?
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Old 2nd March 2007, 09:20 PM   #4
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''At current time Svet produces excellent 6550C's and no need to look further......althought I am informed the coke bottle Tungsol version can take a higher B+; i.e closer to the golden oldie A version. I don't know if this is true. Other DIY members could input....reliability etc
I'm currently using Svet 88's with a duration clock sofar accumulated 500hrs at 50mA @ 500V and all are emission stable. (a well made KT88 used under such AB conditions should last 10,000hrs min). ''

This comes from best 6550's thread. Can this be for running at 25W? Imagine me wanting 15W... It will outlive kindergarden.
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Old 3rd March 2007, 01:18 AM   #5
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The tubelab.com site has an interesting bit on tube life somewhere. He contends that running the tubes at a higher voltage but a lower bias current will give a longer life for the same power due to reduced stress on the cathode. IIRC, that means using a higher impedance primary in the output xformer (like 5000 ohms instead of 3500).
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