Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on September 01, 2017, 04:52:29 pm

Title: 6AX5GT
Post by: TIMBO on September 01, 2017, 04:52:29 pm

Hi guys, I'm looking for a 6.3v octal rectifier for a low watt 6V6 SE amp.

Will these work. Thanks

Title: Re: 6AX5GT
Post by: sluckey on September 01, 2017, 05:05:31 pm

Yes. And since the cathode is not connected to the heater you can use the same 6.3v circuit as your other tubes.

     https://frank.pocnet.net/sheets/049/6/6AX5GT.pdf

Title: Re: 6AX5GT
Post by: TIMBO on September 01, 2017, 05:19:32 pm

Thanks sluckey, Don't see it used much, thought I'd better check.
The PT has a separate 6.3v winding.

Thanks

Title: Re: 6AX5GT
Post by: TIMBO on September 01, 2017, 05:22:02 pm

While where on the subject, I found this http://www.angelfire.com/electronic/funwithtubes/rectifiers.html (http://www.angelfire.com/electronic/funwithtubes/rectifiers.html)
A good reference guide.

Title: Re: 6AX5GT
Post by: DummyLoad on September 01, 2017, 05:37:10 pm

bogen favored 6AX5GT in small stuff from their pre SSR days. no need for 5V winding. models k15, CHA-20 etc...

decent recto - still relatively inexpensive and available. i have revamped several, 2 k15 and 2 CHA-20.   

--pete

Title: Re: 6AX5GT
Post by: tubenit on September 01, 2017, 05:54:50 pm

I think on one of the Bogens with that rectifier that the first electrolytic in the B+ rail was only a 10uf in the one I owned?   Then the following one was 20 uf or higher, IIRC?   I think there is a low capacitance rating for that tube.

This schematic doesn't reflect what my Bogen actually had but it's worth noting the electrolytic values in the B+ rail

http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20.pdf (http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20.pdf)

OK, I found a schematic of the one I owned and made a conversion into a Carolina Blues Special.  It did have a 10uf as the first value and then 20uf as the next value.

http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20_conversion.pdf (http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20_conversion.pdf)

Tubenit

Title: Re: 6AX5GT
Post by: DummyLoad on September 01, 2017, 06:39:04 pm

Quote from: tubenit on September 01, 2017, 05:54:50 pm

I think on one of the Bogens with that rectifier that the first electrolytic in the B+ rail was only a 10uf in the one I owned?   Then the following one was 20 uf or higher, IIRC?   I think there is a low capacitance rating for that tube.

This schematic doesn't reflect what my Bogen actually had but it's worth noting the electrolytic values in the B+ rail

http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20.pdf (http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20.pdf)

OK, I found a schematic of the one I owned and made a conversion into a Carolina Blues Special.  It did have a 10uf as the first value and then 20uf as the next value.

http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20_conversion.pdf (http://el34world.com/charts/Schematics/files/bogen/bogen_cha-20_conversion.pdf)

Tubenit

the 6AX5 has a lower plate peak current rating than most rectifiers - average plate current is 125mA, like 5Y3GT but peak is 375mA vs. the 5Y3GE's 450mA - so a small-er filter is in order. 10-22uF is suitable, 33uF would probably be pushing things. IIRC i used 32uF/32uF cans. spec sheets state 10uF filter.


--pete

Title: Re: 6AX5GT
Post by: TIMBO on September 01, 2017, 07:13:01 pm

Thanks guys, My next thought is what the voltage drop will be?
The PT is 280-0-280v and with a EZ81 I might get about 340v after rectifying.

Title: Re: 6AX5GT
Post by: sluckey on September 01, 2017, 07:25:55 pm

Quote

My next thought is what the voltage drop will be?

It's not a fixed value. Depends on the load current.