Hi Allan,
The bridge rectifier that you are asking about is usually used to make DC output out of an AC input. I have drawn you a diagram of how it works.
I would have thought that they will already have one in each PSU anyway. Besides a single diode on the output rail should be enough to stop any problem.
Wow! Nice drawing......
.....Yeah, .... already got this far but apparently , can't trust the on-board Diode on the + rail ..... having the same PSU amp-age / voltage feeding down the Positive rail wasn't factored into most designs
......so yes....sort of right ....but have to beef-up the safety substantially .... I think I know what to do but always open to ideas..... please, keep the information coming in please!
Have included how I think I'll proceed but nowhere near the drawing quality as......well maybe I need better pencils
Aussie Allan