Filament Wiring

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DMOD:
The Filament supply schematic below should suffice for a grid-driven 807 Linear Amplifier.

No need to complicate things.


Phil - AC0OB

WZ1M:
Is the filament transformer a "REAL" 120 vac primary? If its a 110, 115 or a 117 vac primary, your going to be running closer to 7 vac on the filaments. Not to worry on the filament side but if the transformer is not heavy enough, it will saturate and cause high current draw on the primary. If your house line voltage is running near 124 vac, which many now do, your looking at close to 7.5 vac filament.
Just my confusing two cents.
Regards,
Gary...WZ1M

W9ZSL:
Hey Fred. Stay asleep. I guess you missed the point or didn't comprehend the question. I've seen diagrams where the filament transformer for an amp was wired so that the secondary center tap was grounded and both sides were run to the final. I've also seen (and used) ONE wire to the filament with the other grounded to the chassis. My question was IS THERE AN ADVANTAGE TO USING ONE METHOD RATHER THAN THE OTHER? Case-in-point: NOTE THE DIAGRAM BELOW.

W9ZSL:
Gary. It's 117.

KA2DZT:
Quote from: W9ZSL on September 22, 2018, 12:05:51 PM

Hey Fred. Stay asleep. I guess you missed the point or didn't comprehend the question. I've seen diagrams where the filament transformer for an amp was wired so that the secondary center tap was grounded and both sides were run to the final. I've also seen (and used) ONE wire to the filament with the other grounded to the chassis. My question was IS THERE AN ADVANTAGE TO USING ONE METHOD RATHER THAN THE OTHER? Case-in-point: NOTE THE DIAGRAM BELOW.


Mike,

The schematic you posted with the 4-250s is correct for those tubes because they are directly heated cathode tubes.  Those tubes do not have separate cathodes so you must use a filament xfmr with a CT.  Your amp is using 807s which do have a separate cathode so you would normally ground one side of the filament xfmr and run only one wire to the filament just like what is shown on your 807 amp schematic.

I'm going back to sleep,
Fred

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