I remember seeing in QST a primary voltage regulator ( with tyristors )
sensing the secondary high voltage by means of a voltage divider. Much
better than a reostat or a Variac. In a filament stabilizer/adjuster you use
instead the rectified secondary voltage as reference.
If you use this method in a anode supply, your anode voltage will then be
the same if you use a constant or a pulsed tune-up carrier. And your final
tube sees the same anode impedance in both cases. This is usually not the
case with present days condenser input filters - there it is better to use
pulsed tune up. The anode voltage and the anode impedance will then be
almost the same as when you run SSB and better because of less anode
dissipation.
I do not know if this primary regulator sends out any QRM and probably could
transients on the mains be a problem. Anyhow, will try to find this QST
paper and will let you know more later.
Hej daa de Hans / SM5KI
----------
>Fr?n: "G0MJW" <mike@g0mjw.freeserve.co.uk>
>Till: "Jon Ogden" <jono@enteract.com>, "AMPS" <amps@contesting.com>
>?mne: Re: [AMPS] A look underneath the Ugly amp. chassis.
>Datum: tor 4 nov 1999 09.51
>
>
>
>> > A rheostat in the HV transformer primary is bananas.
>>
>>
>> Why? Too much loss?
>>
>
>No, because it will wreck the regulation. Most amp PSUs use capacative
>filters after the rectifier to provide the HV supply. A feature of
>capacative filtering is the high ratio of the peak current supplied from the
>rectifier into the filter capacitor with respect to the mean current
>supplied to the amplifier. The proper thing to use on the HV primary is a
>variac.
>
>Rheostat = device whose resistance to electric current depends on the
>position of some mechanical element or control in the device.
>
>Variac = transformer whose transformation ratio depends on the position of
>some mechanical element or control in the device.
>
>
>
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>
>
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