# Need help finding a transformer

#### Jotto

Joined Apr 1, 2011
151
Have looked at digikey, allied, newark, but nothing is close to what I need.

primary 120 vac input 1 amp

secondary 6.3/3.15 center tap 300ma

#### K7GUH

Joined Jan 28, 2011
190
Do you actually need the center tap? If not, see if you can find an inexpensive transformer with a 12 volt center tapped secondary. Connect two diodes across the 12 volt leads, back to back, so to speak. Your 6 volt
fluctuating d.c. across the center tap and the joint of two diodes will give you a reasonable source for a 6 v.a.c. filament. I don't have a working scanner at the moment so can't post a diagram.

#### Jotto

Joined Apr 1, 2011
151
I actually need 3.15vac secondary output. I was thinking of using a 6.3 filament transformer that was center tapped to get the 3.15.

Do you actually need the center tap? If not, see if you can find an inexpensive transformer with a 12 volt center tapped secondary. Connect two diodes across the 12 volt leads, back to back, so to speak. Your 6 volt
fluctuating d.c. across the center tap and the joint of two diodes will give you a reasonable source for a 6 v.a.c. filament. I don't have a working scanner at the moment so can't post a diagram.

#### thatoneguy

Joined Feb 19, 2009
6,359

Filament Transformer
6.3 vct @ 1 amp

However, the price is worse than Radio Shack at $75 (Shipping included) This one looks much better (Down and to the right of the one above in the listing): Filament Transformer 6.3 vct @ 4 amps Primary: 117 vac, 50/60 Hz Secondary: 6.3 vct @ 4 amps Dimensions: 3.675" x 2" x 2-1/4"H$18

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#### MrChips

Joined Oct 2, 2009
22,077

#### Bernard

Joined Aug 7, 2008
5,682
Or how about an old ?-14-X Triad, 117V 60 C.P.S. Fil 6.3C.T.@1.2A, for $5.00, postage paid. Punch up Bernard to send a message. Thread Starter #### Jotto Joined Apr 1, 2011 151 Or how about an old ?-14-X Triad, 117V 60 C.P.S. Fil 6.3C.T.@1.2A, for$ 5.00, postage paid. Punch up Bernard to send a message.
The problem here is that I need 3.15vac. That is why I want a 6.3vac center tap. The best one is with Hammond. 110vac dual primary, dual secondary of 3.15vac courtesy of Mr. Chips.

Thank you for the offer though.

Joined Dec 26, 2010
2,148
If your requirement is for an accurate 3.15V at only 300mA, beware of the possibility that a filament transformer designed to deliver a very much higher current may give more voltage than its rated value. Not all transformers are rated this way, but because filament voltages are fairly critical, it is not uncommon for the turns ratio of a filament transformer to be corrected for the voltage drop on load.

As a matter of interest, what is the 3.15V AC for?

#### Jotto

Joined Apr 1, 2011
151
As a matter of interest, what is the 3.15V AC for?
I am making a curve tracer