[AMPS] Filament circuit design

[Chris W Tran]

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)   I would never ever monitor the current on
the HV+ side !

I seem to remember a circuit which overcame this problem - maybe
in an old RSGB or ARRL Handbook ?

Thanks - 73
Chris  GM3WOJ/GM8V
<chris.tran@zetnet.co.uk>


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