Bench PS regulation

[brandes.cm]

I have a 20 amp fixed voltage supply that started life at 12Vdc. It has since started regulating at 15.8Vdc. This is a magnetic supply I believe and no regulation anywhere. What is the best way to add a voltage adjustment on the output of it.

Thanks,
Cory

[Perry Babin]

I'm not sure what a magnetic supply is but for a standard, unregulated power supply, you'd use an LM723 and several high-current pass transistors. There is a sample of a regulated circuit in the following manual.
http://www.bellscb.com/products/test...ps-52kx_om.pdf

One problem that you may have is that there is very little headroom unless the supply can produce more than 15.8v.

Do you simply want to reduce the voltage or do you want true regulation?

[brandes.cm]

I simply want to reduce the voltage with some adjustment.

The supply internals are nothing more than a transformer and some caps. No semiconductors at all.

[Perry Babin]

The simplest thing may be to wire a light dimmer in-between the mains and the supply. There are many different ways to do it after the rectifiers but it wouldn't be as easy as the dimmer.

[brandes.cm]

I will give that a try.