Toroidal Tranformer Question *PIC*

[hongrn]

Hello all,

I am interested in this buyout for a LM4780 kit I'm building. Load capacity is 350VA, secondary voltage is 55V + 55V. However, I only need 25V + 25V for my kit. Is there an easy way to bring down the voltage from 55 to 25? Or should I go ahead and buy the 25V + 25V instead? Thanks.

Hong

[cjd]

> Or should I go ahead and buy the 25V
> + 25V instead? Thanks.

Just get what you need. Unless you run some pretty well heat-sinked regulators, which is the other way. But unless you already had plans for regulation, it won't save you any money.

C

[wg_ski]

> Hello all,

> I am interested in this buyout for a LM4780
> kit I'm building. Load capacity is 350VA,
> secondary voltage is 55V + 55V. However, I
> only need 25V + 25V for my kit. Is there an
> easy way to bring down the voltage from 55
> to 25? Or should I go ahead and buy the 25V
> + 25V instead? Thanks.

> Hong

A 25-0-25 will give you +/-35V or thereabouts. If you need +/-25VDC, you need an 18-0-18 tranny.

It can't be done with this particular one, but if you need half the AC volts, you can wire the primaries in series for 220/240V if it's a dual. They run quieter that way, too.

[rudyjakubin]

> A 25-0-25 will give you +/-35V or
> thereabouts. If you need +/-25VDC, you need
> an 18-0-18 tranny.

> It can't be done with this particular one,
> but if you need half the AC volts, you can
> wire the primaries in series for 220/240V if
> it's a dual. They run quieter that way, too.

25 x 1.414 = 35 volts.
18 x 1.414 = 25.5 volts.
The Caps bring up the rms voltage to peak voltage.

[jaudio]

> Hello all,

> I am interested in this buyout for a LM4780
> kit I'm building. Load capacity is 350VA,
> secondary voltage is 55V + 55V. However, I
> only need 25V + 25V for my kit. Is there an
> easy way to bring down the voltage from 55
> to 25? Or should I go ahead and buy the 25V
> + 25V instead? Thanks.

> Hong
Why not use the 16.2volt secondries

[hongrn]

After rectification, I need to end up with 35VDC, so the best thing is to buy a new toroid. I was hoping to save some money with the buyout, but in the end, I still need to shell out $50 for a new toroid. :-(

[jaudio]

> After rectification, I need to end up with
> 35VDC, so the best thing is to buy a new
> toroid. I was hoping to save some money with
> the buyout, but in the end, I still need to
> shell out $50 for a new toroid. :-(

Buy two 129-084 25v. That 35volt after rec.

[jonpike]

> Why not use the 16.2volt secondries

Wish there were real specs available on those things. Odds are, the 16V ones are lower power
thin gauge secondaries for powering some low level electronics, while the 50V-0-50V winding would be heavier, and supply the majority of the 350VA total power.

Or not... since we have no idea what it was originally for.. price is the blessing, and lack of knowlege is sometimes the curse of these buyout things.

[colby]

Provided Link: Surplus Transformer


Almost 600 VA and 44VCT tranny for $25.