Got my hands on another board long enough to get enough pictures to reverse engineer it.

Just want to throw this out there and see what the knowledge base here thinks... look at C2 and C3. It sure looks like they are hooked up in opposing polarities?

Also attached is the schematic i've worked out of the board - it's a power supply / relay board for a load control receiver.

 

Do you have the capacitors C3 and C5? Or you got the board like that?
Because I don't think they are electrolyte capacitors.

 

I suspect C3 is a bypass capacitor. Why they show a "+" on the silkscreen may be some artifact left over from the design software. C2 is the only electrolytic cap, and its "+" sign is much bigger than the rest.
If this turns out to be an AC supply (no rectifier diodes), then C2 and C3 would not be installed. Output would be on AC1 and AC2, there would be no "DC" output

 

I think sagor's reasoning might be the closest to what I'm seeing.

This board could be populated in a few different ways depending on the specific application... there are other boards within this system that had parts or pads thereof that were normally unpopulated, but the boards were never redone to remove options that nobody ever ordered.

My guess is that the capacitors and diode bridge only saw use in 'remote relay box' applications and the resistor vs jumper allowed the use of 5V relays instead of standard 12V relays.

 

You CAN use two electrolytic caps back to back to form a non-polarity specific capacitor. Here's a picture.
Image deleted.

 

Math ?

 

You CAN use two electrolytic caps back to back to form a non-polarity specific capacitor. Here's a picture.
View attachment 356287

Wouldn't that be 5uF total??

 

C2 and C3 are parallel. I'm now of the belief C3-C5 are intended to be axial ceramic.

 

You CAN use two electrolytic caps back to back to form a non-polarity specific capacitor. Here's a picture.

As is comonly done with motor Start capacitors to pass AC via dry electrolyte caps.

 

Wouldn't that be 5uF total??

I might have that backwards. In fact, yeah, I think so.

 

Corrected image.
View attachment 356347