Subwoofer DC polarity riddle

[DWI116]

I have a B&W ASW2500 Subwoofer that stopped working. I opened it up to take a look and found a couple of dead capacitors with an ESR meter, which I have replaced. I took pictures of everything as I disassembled and was just checking against the pictures as I buttoned it up. See the two attached pictures. DC power connection was reversed from 1st circuit board to the 2nd (Pic 1). It was this way on the working Sub, before I dissembled it. Red wire clearly soldered to the positive input on the 2nd board (Pic2) and Black to negative (not pictured). Power inputs to the first board were not reversed. What I know about electronics is self-taught, so I'm looking for some help. I know that sometimes circuit boards get mislabeled in production. That's a possibility here, but seems unlikely in a B&W product where I would expect a high standard of quality control. On the other hand, I'm hesitant to just reverse it and try it. Getting the polarity wrong usually results in instant destruction. Absent a better idea, my plan is to disconnect the reversed power leads and test with a multi-meter if the power output from the 1st board is correct or reversed. If it is reversed then I'll just go with that and assume the circuit board was labeled wrong. If not, is there a way to test on the input side on the 2nd board? Is it possible this sub was thumping away for years with polarity reversed, inadvertently, in production? From what I know, that seems unlikely in a DC circuit.

[DWI116]

May be a coincidence, but I just noticed in posting that the capacitors in the 1st picture, 3 large and 2 small, are the ones that went bad and that I just replaced. Hmmm...

[g1]

If it was working that way and no caps blew up, I'd suspect the labeling is wrong. You should be able to check resistance from the caps + and -'s to the DC lugs.

[Greg Robinson]

Sure looks like the labelling is wrong - the side with the faston connectors it's obvious the connector labelled + is connected to the ground plane.

[Tom Phillips]

Does the B&W ASW2500 Subwoofer use both positive and negative supply voltages? Maybe that would explain the apparent grounding.
Is there a schematic available?

[Tom Phillips]

No joy trying to find a Service Manual or schematic for the ASW 2500.
I did find a discussion post at https://forums.audioholics.com/forum...ly-died.88329/ that included a users comment that he received the following from B&W support way back in 2013.
"To determine if the problem is the amp or the woofer the woofer should be removed and tested. you can connect one of your speaker wires direct to the woofer to test to see if it is still operating. you can also bring it to a local repair shop to have them test the woofer as well. if the problem is the woofer we do have replacements available for purchase at the link below. if the woofer is still good and the problem is the amp then you will want to find a local electronics repair shop to have them try to repair the unit. we are unfortunately unable to service this model as we are no longer able to get parts but we do have one shop we typically recommend that has worked with these amps before." Sounds like it was always difficult to get support for the unit.

[g1]

No joy trying to find a Service Manual or schematic for the ASW 2500.

I wonder if the 2000 would be close enough:

https://www.manualslib.com/manual/10...s-Asw2000.html

[Tom Phillips]

I wonder if the 2000 would be close enough: https://www.manualslib.com/manual/10...s-Asw2000.html

Nice find g1. That ASW2000 schematic is probably close enough to tell us that the B&W approach is to use a bipolar power supply design for the output stage and that would explain the connections that DWI116 is seeing in his unit. Therefore, if the unit is put back together with the new capacitors in their original positions, it should be safe to turn the unit on without the speaker connected. Then the power amp supply voltages can be measured to verify that they are of opposite polarity and equal value. If there is no DC voltage reaching the output connections, then the speaker can be connected and, hopefully, the unit will be fully operative.

Hopefully, this new information explains the initial confusion.
Other newsgroup discussions indicated that no-one has found service information for the ASW 2500 model.