Hello

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Thanks Alek for resuming the dialogue. You are the only one who has reported this risk of non-degassing to me. Like me, you are faced with a reduced regulatory RF power

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You had told me

/g/ham-amplifiers/message/40898

that the gettering was done by the anodes.

If you run 500W PEP only, your tubes will quickly become gassy. They have no separate getters. The gettering is done by the anodes and so they must become red during operation to keep them healthy.

This happens in Australia as well where we have 400W PEP limit. At that level, the anodes never get red, so the tubes fail very quickly.

You will need to exercise your amplifier at full power regularly to ensure healthy tubes.

This risk does not seem to worry the other participants at all.

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Your point is confirmed in this document

https://www.w8ji.com/Amplifiers.htm

The fastest way to ruin a 3-500Z or other glass electric grid tube is to never expose the anode color for an extended period of time! Storing a 3-500Z tube for many years without using it almost guarantees that a breakdown will occur the first time a high peak voltage is applied to the anode.

Since the tubes had not been used for 15 or 20 years, I did not want to expose them to the risk of arcing due to imperfect degassing. So I came up with a solution, which I have outlined, to make the plates glow under a relatively low anode voltage by applying a positive voltage to the grid (actually positive to the cathode).

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I proposed

·???????? To use the SSB position 2500 V 220 mA only to periodically degas the tubes and this without RF

·???????? To use the CW position 1700 V 175 mA during real SSB traffic with RF=500W

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Eventually, I can find a solution so that in CW position the anode current is lower.