Thanks, we dont have access to any of the "external" stuff...that is what the customer would put in, and we wouldnt be able to add capacitors there.
As you can see, when we put the bridge in to handle reverse polarity, we then find that the "return" of the 16V line, wont follow the 16V line any more......due to the ground connection inside the unit as shown....this internal ground connection , as shown, unfortunately shorts out the bridge rectifier diode.
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As you can see, there is a connection back to GND inside the unit, (via the return of the 0-24V connection), which unfortunately shorts out the lower rectifier diode of the bridge.
As such, i put in the lower diode in schem 2 to mitigate this...putting it in the 0V return of the 0-24V connection.