>
>Hello all
>
>I'm constructing a tetrode amp. and the filament transformer
>I have has no centre-tap. I do not want to 'earth' one side
>of the filament.,
>
>Any suggestions as to how I can monitor the cathode current ?
>(The HV- would normally be connected to the centre-tap of the
>filament xfmr. and the cathode current metering between this
>point and 'earth') One idea I had was to make an 'artificial'
>centre-tap by connecting a low-value wirewound resistor to
>each side of the filament, and take the HV- to where they join.
>(checking that not too much filament AC current flows through
>these 2 resistors)
The 2-res. artificial CT works ok. Typically, 5-10% of the rated
filament current flows through the artificial CT. Another method is to
wind a 7.5vac or so 60Hz CT autotransformer. The wire size can be quite
small since the current in each wire is half the cathode current.
- later, Chris.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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