Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on October 13, 2022, 05:56:14 am

Title: Back-To-Back Power Transformers
Post by: TIMBO on October 13, 2022, 05:56:14 am

Hey guys,
At the local electronics store an can get some low voltage transformers cheap.
They are versatile with their multi tap secondary's
Putting them back to back I can get a 240v HT or other voltages with connecting the secondary taps of different voltages.
The main power transformer has a 6.3v at 1A which great for one 6V6 and 12AX7 and a bit spare for the HT.
(https://i.imgur.com/2fZjXrM.jpg)
I would usually tie one side of the wiring to ground, works well.
In the above drawing I have added an artificial CT via two 220 ohm resistors.
IS thid OK to do???
Or even better tie the two resistors to the 6V6 cathode.

Title: Re: Back-To-Back Power Transformers
Post by: Willabe on October 16, 2022, 01:52:42 pm

Quote from: TIMBO on October 13, 2022, 05:56:14 am

Hey guys,
At the local electronics store an can get some low voltage transformers cheap.
They are versatile with their multi tap secondary's
Putting them back to back I can get a 240v HT or other voltages with connecting the secondary taps of different voltages.
The main power transformer has a 6.3v at 1A which great for one 6V6 and 12AX7 and a bit spare for the HT.
(https://i.imgur.com/2fZjXrM.jpg)
I would usually tie one side of the wiring to ground, works well.
In the above drawing I have added an artificial CT via two 220 ohm resistors.
IS thid OK to do???
Or even better tie the two resistors to the 6V6 cathode.

.

Title: Re: Back-To-Back Power Transformers
Post by: TIMBO on October 16, 2022, 02:14:48 pm

.



Toilet paper shortage now ink  :l2:
Thanks Willabe

Title: Re: Back-To-Back Power Transformers
Post by: shooter on October 16, 2022, 02:36:05 pm

 :laugh:
it's invisible, just pour lemon juice on your monitor to see it
we have plenty of TP now, it's just 100% more to buy

Title: Re: Back-To-Back Power Transformers
Post by: glass54 on October 16, 2022, 07:35:35 pm

Hi Timbo
Done it many times for small combos but especially for 1RU preamps. In the case of Preamps I've used a 15VA 12.6V tx for input (Heaters) and a 5 to 7VA Tx reversed for HT.
Regards
Mirek

Title: Re: Back-To-Back Power Transformers
Post by: TIMBO on October 17, 2022, 01:35:30 am

Thanks guys, The guys here gave it the nod as well

Title: Re: Back-To-Back Power Transformers
Post by: kagliostro on October 17, 2022, 03:30:19 am

Ciao TIMBO

Back-To-Back Power Transformers is the title of this thread

so, may be you are interested on this (I developed it some time ago with a friend)

Franco

Title: Re: Back-To-Back Power Transformers
Post by: TIMBO on October 17, 2022, 05:20:53 am

Thanks mate, That's good to know.
I like the -30 for a bias supply.
Thanks

Title: Re: Back-To-Back Power Transformers
Post by: Willabe on October 17, 2022, 11:59:12 am

Quote from: TIMBO on October 16, 2022, 02:14:48 pm

.

Toilet paper shortage now ink  :l2:
Thanks Willabe

:laugh:
I was just giving it a  :bump1: