RE: [CAD_CAM_EDM_DRO] Power supply

A buck transformer would be the simplest way to go.

Your jump from 65 to 90 is because the capacitor "floats" up to the peak
waveform voltage while the voltmeter measures the average. Take the
lower number and multiply by 1.4 to get an approximation.

Another option is to use the transformer from an old microwave oven.
These are rated for several hundred watts and due to the high voltage of
the secondary, the primary and secondary windings are separate so it is
easy to take a cold chisel and remove the secondary and wind your own.
(about one turn per volt)

I still have a number of transformers which I sell for $20/smaller and
$30/larger.
Shipping to any USA address is included in the price.

Dave

> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of David Speck
> Sent: Saturday, June 24, 2006 6:37 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Power supply
>
>
> Mina,
>
> A simple solution would be to find a 12 volt transformer with
> a 10 amp
> or so output rating, and wire its output winding in series with the
> primary of your original transformer so that the 12 volt
> output of the
> new transformer opposes the line voltage going onto the original
> transformer. This will reduce the primary voltage by 10%
> (assuming that
> the original transformer runs on 120 VAC), and thus lower the output
> voltage by the same proportion. No winding cutting or
> removal required
> that way.
>
> This arrangement is called a buck transformer in industrial parlance,
> and you can find boost/buck transformers on eBay easily.
> Depending on
> the polarity of the wiring, they can boost or buck the line
> voltage by a
> certain amount.
>
> You have a 50/50 chance of connecting the setup right the
> first time.
> If you have the wrong relative polarity, then the supplemental
> transformer will raise the voltage by 10%. Just reverse the
> polarity of
> any pair of the transformer primary leads to change things around.
>
> HTH,
> Dave
> >>>
> >>> I'm trying to rebuild the power supply that came with an
> old lathe,
> >>> the Transformer is good I took 65 AC from the output fed it to a
> >>> bridge to get the DC and then on to a Capacitor.
> >>> The thing is the DC voltage after the bridge is stable at
> 65 VDC but
> >>> after the Capacitor it grows up to 90 VDC which is too
> high for my
> >>> Geckos 320.
> >>>
> >>> Any advise?
> >>>
> >>> Mina F.
> >>>
> >
>
>
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