Toroidal center tap, or not to tap that is the ?

I have a toroidal transformer with no center tap. this is a 330 vac primary with dual secondary 60vac in series and 30vac parallel. If I understand this correctly in series the two joined wires will be a ground/center tap? but this doubles my required voltage. I'm looking for the best method for a fix to the issue. Use it without the tap or reduce the voltage and have the tap.
Your thoughts on how to do both are appreciated. Less
Photos below I hope!
 

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Specs. for the transformer are shown in the attachment to post #4. the amplifiers are Naim 140 clones (X2), With the transformer wired in series after after the full wave rectifier and capacitor I have a out put of 43.1 Vdc with no load, that is 3.1 volts more than the maximum recommended input by the manufacture for the Naim 140's. How to and what to use to regulate the 43.1 Vdc to within the required spec?
 
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Wire the primary up to a bulb tester and measure what the secondary voltages really are.
MOOLY, I am not sure what that is, a bulb tester? A 120v lamp wired into the primary before the transformer???? did you mean wire into the secondary for a load? I'm confused, I need a photo or sketch or a clarification. I searched in here for something on it and didn't get much.
 

Bibio

Member
2009-03-08 3:36 am
You are still not making sense. You keep showing manufacturer data for a 117/234vac transformer? Are you mistaking the 300 va rating for the primary voltage? Are you describing no load measured data?

as above.

your transformer is 117vac/234vac primary with 2x30vac or 1x60vac secondary rated at 300va (power). its not a 300vac input voltage. just ignore the 300va.
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Bulb tester. I found this but I don't understand what or how this is going to tell me anything about the output voltage of my secondary's? And also would this not simulate a simple soft start circuit?

The bulb tester is a safe way to power up circuitry (and transformers). If you got a primary connection wrong (trying different tappings or identifying unknown windings) then the worst that happens is that the bulb lights.

Its just a visual current limiter. Its not really a soft start because the bulbs filament resistance is actually lowest when cold.
 
You are still not making sense. You keep showing manufacturer data for a 117/234vac transformer? Are you mistaking the 300 va rating for the primary voltage? Are you describing no load measured data?

MY mains voltage is a constant and consistent 120vac I am the first drop from the transformer so I am blessed with consistant mains voltage.The specs.for the transformer that I purchased are exactly what is posted. If the primary voltage you refer to is the mains voltage it is 120vac if other I would not know how to test or calculate for it. As to the secondary voltage of 43.0 vdc this was taken after full wave rectification thru a 600v 50amp bridge rectifier and one 4700uF capacitor on a bread board with zero load. I assume that there will be a voltage drop on the secondaries with a load applied. What would be a good educated guess as to what this drop would be. My concern is that I am investing a fair amount of time and effort into this project and would very much like to avoid blowing up my amp board, hence my concern for the additional 3 volt secondary voltage, the 40 volt input is the manufacturers spec. for the kit and is the highest voltage that I have encountered in my research of the Naim 140 amp, that is also reason for my concern, is this 40 volts maybe the upper end of the tolerance. Pic is of my first board completed minus a bunch of other stuff.
Thanks, Less
 

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