Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Leevi on March 07, 2015, 02:47:44 am

Title: Is this a good idea?
Post by: Leevi on March 07, 2015, 02:47:44 am

I have a simple PT that only have 6,3V and 250V secondaries.


I would like to use it with 5Y3 rectifier and I'm thinking a solution how the PT could be adapted for 5Y3.


See the attached picture.


I see at least the following problems:
- High DC voltage on the tube heaters
- 6,3 V filament reference point, the resistors must be big in order to keep current low.


/Leevi

Title: Re: Is this a good idea?
Post by: AZJimC on March 07, 2015, 03:05:59 am

I don't see a way your 6.3vac could be balanced to ground without providing a path to ground for the B+. I'd think about using an EZ81. It has 6v heater, and cathode is not connected to heater. Also could look at other variants in octal if you prefer. Look at a 6AX5GT. It is similar, but in octal basing

Jim

Title: Re: Is this a good idea?
Post by: Leevi on March 07, 2015, 03:09:31 am

Yes I agree, EZ81 is a better alternative for this.
/Leevi

Title: Re: Is this a good idea?
Post by: kagliostro on March 07, 2015, 03:09:48 am

+ 1 for AZJimC

The 5Y3 cathode is directly heated, if you use this kind of tube you'll have B+ on filaments and that is'n a good thing to do

EZ81 is the solution, reserve the 5Y3 for one other project

Franco

Title: Re: Is this a good idea?
Post by: darryl on March 07, 2015, 03:27:10 am

If there is space on or under the chassis, a 2 amp filament transformer could be installed, to provide an electrically isolated supply for the rectifier's heater.