Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: isaac_teller on October 31, 2023, 12:47:54 pm

Title: National Deluxe schematic
Post by: isaac_teller on October 31, 2023, 12:47:54 pm
Hello. Is it reasonable that the volume and tone potentiometers would have such relatively low values? wouldn't 500K be about right? I'm building a clone with a few additions(master volume, grid stops on input and screen grids, capacitor and cap on input triode).


https://el34world.com/charts/Schematics/files/Valco/National_deluxe.jpg (https://el34world.com/charts/Schematics/files/Valco/National_deluxe.jpg)
Title: Re: National Deluxe schematic
Post by: PRR on October 31, 2023, 02:10:28 pm
It's odd. It's not broken.
Title: Re: National Deluxe schematic
Post by: sluckey on October 31, 2023, 02:26:27 pm
Quote from: isaac_teller on October 31, 2023, 12:47:54 pm
capacitor and cap on input triode
Huh? Did you mean cap and resistor? That .05 cap and 6.8M resistor are necessary for proper grid leak bias. I think adding a grid stopper on the input triode is not worth the effort.
Title: Re: National Deluxe schematic
Post by: isaac_teller on October 31, 2023, 04:27:34 pm
My mistake. I meant cap and resistor on the cathode of the first triode and removing the .05 cap and 6M8 resistor.
Title: Re: National Deluxe schematic
Post by: ALBATROS1234 on November 30, 2023, 10:14:43 am
Man, you must have some sag on those 6L6's with a 6X5. I wonder why they used that rectifier? I get maybe they wanted to skip out of the extra 5v winding but there are better 6V rectifiers that supply more ample current.
Title: Re: National Deluxe schematic
Post by: ALBATROS1234 on November 30, 2023, 10:20:13 am
I just saw you are building a clone. If you have the current available try a 6AX5, same pin out as the 6X5 but a much more robust rectifier. My latest build the PT and chassis came from a 1954 Revere R2R which used a 6X5 I was a little worried the PT might get hot with a 6AX5 so I bought a $15, 6.3v @ 1.5a trannie and let the PT just power the filaments for everything but the 6AX5 and used the small filament transformer just for the 6AX5. Works like a charm.