[AMRadio] Modulator question


Paul Baldock paul at paulbaldock.com
Sun Jan 31 10:38:46 EST 2016


The screen is not tapped on the mod tranny. It is pure DC. at about 
half the plate voltage.

I think however the issue may be related to the screen, because in a 
typical EL34 output the screen is run at the same voltage as the 
plate. I did not do this because my plate voltage is about 660V.  I 
will try upping the screen voltage (and readjusting the bias of course)

Thanks

- Paul

At 04:30 AM 1/31/2016, Jim Tonne wrote:

>If the screen voltage is derived from a tap on the primary
>on the output transformer, NO bypass to ground from the
>screen.   The dead giveaway on that is the triangular
>waveform appearance.   That means the load is capacitive
>and this can be caused by a capacitance somewhere,
>either on the secondary or the primary.
>
>Remove the capacitor from each of the screens to ground.
>
>- Jim Tonne W4ENE
>
>
>
>On 1/31/2016 1:12 AM, Paul Baldock wrote:
>>At 09:15 PM 1/30/2016, Jim Candela wrote:
>>>power. Perhaps try bypassing the screen tap with a bypass 
>>>capacitor, like 50 mfd or so.
>>
>>It's bipased with 390uF
>
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