Craig wrote:
>
>What is "safe" practice in a grounded screen tetrode amplifier where
>the requirement is that the power supply negative rail is left
>"floating" ?
>
>It always makes me nervous poking around a grounded screen amplifier
>when some parts of the circuit is below chasis potential and the
>negative of the power supply is left floating.
>
Me too. I don't think there is any wonderfully safe way, as all three
power supplies - HV, grid and screen - are only connected to chassis
through the G2+ connection. In particular it needs a fully floating HV
supply with a very well insulated negative side.
DC grounded screen isn't a configuration I would ever choose willingly.
The only exception would be in a UHF tetrode amplifier using concentric
coaxial cavities where the screen has to be grounded for reasons of
mechanical construction. (Gerald K5GW is the local expert on that.)
At lower frequencies I would much prefer to tackle the problems of RF
bypassing the screen grid, and operate with the cathode DC grounded in
the normal way.
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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