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#### eduard

Hello,
For my next project i want to use some split bobbin transformer from Triad.
It says on the PDF that
Primary and secondary windings are designed to be connected in series or parallel. Winding are not
intended to be used independently.
Does that mean that if i need 5V 2A i cannot just take one secundairy that can give 5V 3A and not use the other one. If i will have to put the secundairies in parallel i will have 5V 6A and that will mean a higher voltage dropping resistor to get 5V if i wan use it for a 5R4GYB rectifier.
I can imagine a little it that if the two secundairy windings will be used for 2 separate circuits with different current consumption.
Greetings, Eduard

#### Osvaldo de Banfield

From your description, I understand that the traffo is capable to give the voltages and the currents specified, but was not designed to support large voltages across the secondaries, I believe that they are winding simultaneously (Bifilar)), so the isolation between secondaries is only the wire varnish (Say, no m ore that 70-100Vbetween them).

#### eduard

Hello,
The primary and secundairy windings are next to each other so there wl be no need for an electrostatic screen.
I just mailed to Triad in California and will let you now once they answer if they do.
greetings, eduard

#### Attachments

• vpp10-3000.pdf
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#### Osvaldo de Banfield

One winding means 5V @ 3Amper, two in parallel are 5V @ 6Amper, and two in series 10V @ 3 Amper.

#### audiopro

Why would putting the secondaries in parallel change your dropping resistor?. The size of that resistor depends on the current draw of the load and the voltage you need dropped. If you're relying on voltage sag to take some of the drop, then your transformer will have a short life.

#### eduard

Hello,
That is what i know.
BUT it also says:
Primary and secondary windings are designed to be connected in series or parallel. Winding are not
intended to be used independently.
So can i just use one 5V 3A to lit up my rectifier and leave the other 5V 3A unused??
greetings, eduard

#### eduard

Why would putting the secondaries in parallel change your dropping resistor?. The size of that resistor depends on the current draw of the load and the voltage you need dropped. If you're relying on voltage sag to take some of the drop, then your transformer will have a short life.

If the transformer can deliver 6A by putting the two windings in parallel i expect the voltage to be a little higher compared to using one 5V 3A if the current taken by the rectifier remains the same.
Greetings, eduard

#### Osvaldo de Banfield

No, surely the secondaries are bifilar, say, the two wires are coiled simultaneously. The insulation between them is what don't allow to use them separately. But if you want to power the rectifier's heater, use both in parallel and enjoy, no resistor(s) are needed.

#### Bill_P

Accurately measure the resistance of each secondary winding. If they are the exact same resistance, they are bifilar wound. If there is even a small difference in resistance they are not bifilar.

#### eduard

Hello,
I just checked with the two sec. windings in parallel '' feeding '' 5R4GYB ( needs 5V 2A ) . I put one 0,18 ohm in series with the heater . Getting 4,8 at the socket without resistor getting 5,2 volts.
I was expecting a higher voltage. In the end i can use two 0,18 in parallel. But i think both values are close enough.
greetings, eduard

#### mchambin

The data sheet tells wiring in parallel or wiring in series.

It doesn't tell leave some winding unused.
I see no advantage to do so. And the datasheet tells to not use them independently.

Primaries in // for 110V mains, in series for 230V mains.
Secondaries in // for 5 V, in series for 10V ( with center tap 5V 0V -5V )

Silly ? YES, the datasheet is perfectly clear.

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#### eduard

Hello,
Like i have written before i was expecting a higher voltage by creating a 5V that can supply 6A with a load of only 2A.
But problem is solved.
greetings, Eduard

#### gorgon53

I guess it is a core type transformer and therefore both windings must be used.

#### mandu

You ignore the data sheet. It only show the connection possibilities from the terminals. Connect the primary as per data sheet. Series or parallel. This is must. You can have the secondary in series or parallel or use only one or use each of the two secondary windings to different application. No harm. Just do not exceed the current rating of that winding. Regards.

#### wg_ski

Do not exceed the voltage rating either, which implicitly is the end to end voltage of one of the secondaries. Do not get tempted, for instance, to power the heater of the rectifier tube off one and a rectifier and regulator for a DC heater for output or line stage tubes off the other. That puts B+ between adjacent turns and will result in a fireball, eventually. You could power two separate low voltage circuits off of it, provided both never got far above ground and that high isolation (including noise) was not required. The manufacturer still makes no guarantee the two circuits will remain isolated, and if it concerned safety in any way it would not get certification.

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