>A brand new and optimal 8877 (years ago, rarely later) was typically 40-
>50mA for 1.8Kw of output power at VHF (broadcast) with 4Kv HV (loaded).
>As the tube was aging, the RF power decreased and drive was often
>repeatedly increased by guys of the maintenance to obtain again the
>same output and step by step the grid reached levels over 100ma.
>I've also seen 8877 working well over 100ma for different reasons (for
>days, months) without any abrupt failure.
>I'd set with confidence the trip to twice the normal predicted current
>(mostly depend by the applyed HV), beeing aware that some amateur use
>2nd hand tubes that may require high grid to give the desired power.
>Hams have the bad custom to run low HV (or PS with big drops) thinking
>that this is wise not to stress the tube, unluckily this is not always
>true.
>
Indeed. Less anode-V means that more electrons flow through the grid.
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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