Oliver Broad wrote...

>I think I see what's going on, maybe...
>
>There's no smoothing capacitor in your diagram. I bet there's a reasonable
>smoothing cap on the input of the regulator circuit though.
>
>When you measure without the regulator you measure the average of the
>rectified waveform, which is still dipping down to zero between each half
>cycle so you measure a lot less than peak, possibly less than RMS even?
>
>When you connect the regulator there's a capacitor present so it
>peak-detects and reads >50% higher. This is the relevant reading. If this is
>too high you have the wrong transformer.

Duh.  Why didn't I think of that...

That's exactly what's going on, I'm sure of it.

Jai, if you are intending to get +5V and +12V out of this power
supply, there is no need for you to be using a transformer which
puts out so much voltage.  Instead of 50 volts center-tapped, I
think 28 volts center-tapped would suffice.  That would give you
around 18-20 VDC at the input to the regulators.

DD

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