Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dwinstonwood on August 22, 2025, 07:57:24 am

Title: Stand-Alone 5V/3A Filament TX W/CT
Post by: dwinstonwood on August 22, 2025, 07:57:24 am: Hello, when using one of these stand-alone 5V/3A filament TX's with a CT, I need to use/ground the CT, yes?

https://www.hammfg.com/files/parts/pdf/166MS.pdf?v=1697661945

I have a nice 360-0-360 PT but with no 5V secondary. I want to use a 5U4GB to bring down the HT a bit. With a solid-state rectifier it would be something like ~509VDC unloaded which is higher than I want.

Thanks!
David
Title: Re: Stand-Alone 5V/3A Filament TX W/CT
Post by: SEL49 on August 22, 2025, 08:08:06 am: Quote from: dwinstonwood on August 22, 2025, 07:57:24 am
Hello, when using one of these stand-alone 5V/3A filament TX's with a CT, I need to use/ground the CT, yes?
NO! Think about it. There will be B+ on the filaments because the cathodes are connected to the filaments. If you connect the CT to ground you will burn something. Just tape that CT and tuck out of the way. Or do like the old guys did... Connect the CT to the filter caps rather than connecting pin 8 to the caps. I'm one of the old guys.
Title: Re: Stand-Alone 5V/3A Filament TX W/CT
Post by: dwinstonwood on August 22, 2025, 10:58:13 am: Thanks SEL49!

And, now that I think about it (which I wasn't) it's all clear. I like the idea of connecting the CT instead of pin 8 to the reservoir.

David
Title: Re: Stand-Alone 5V/3A Filament TX W/CT
Post by: kagliostro on August 22, 2025, 01:16:41 pm: Ciao Dwinstonwood

Hope this can help

Image Is from this link

https://gammaelectronics.xyz/rider_vacuum_5.html (https://gammaelectronics.xyz/rider_vacuum_5.html)

Franco
Title: Re: Stand-Alone 5V/3A Filament TX W/CT
Post by: dwinstonwood on August 22, 2025, 02:04:10 pm: Perfect Franco!

That's how I'll do it.

Thanks!

David