transformers (Tube Driver?)

[Jason D]

I believe I order the wrong transformer to build a Tube Driver. I know the circuit needs +/- 12.6 V, so I ordered a 12.6 center tap. Does this mean that it puts out 12.6 when not using the center tap?

If I did buy the wrong one, can I still make it work?

[smoguzbenjamin]

I think it''l be double that... :? 25.2v across the end terminals. But you could leave one side unconnected and you'd have 12.6v I think.

[R.G.]

You might enjoy "Power Supplies Basics" at GEO. The article explains the subtlties of transformer voltage versus output voltage.

You have the wrong transformer do to it the easy way. You should have gotten a 24Vct to 30Vct transformer. Each side has to make more than 14Vdc to power a regulator to get a stable +12. The article shows how to look at this.

You can still get away with it, by using a dual half-wave rectifier setup and twice-as-large filter caps. It's in the article.

The stuff at GEO is good background. And its... to quote an old friend... FREE.

[Jason D]

Okay, so the voltage on the transformer is right...now, it is rated for 0.1 Amps. Is that enough? I know that most of my 9V effects only pull  a couple of mA. So, I figured that 100mA would be enough for the Tube Driver.


Is this right?

[Jason D]

RG, I cannot find the Power Supplies basics article at GEO...searched and searched.

Where is it?

[Jason D]

I found the Power Supplies Basics article. But, now I see that I need a transformer that can handle the 150-300mA needed for a 12AX7. So, I will have to order a new one. I am going to get a 25.2V CT rated at 1.0A. And use a 7812 and 7912 to get +/-12V.  

Will the transformer handle that? From what I can tell, it will, but I don't have much pratice with power supplies.

I will just use the 12.6V CT transformer to make a power supply for my breadboard projects.