Polk Audio PSW450 no sound

LAP87

Hi, i recently bought a used Polk Audio PSW450 here in sweden.
The speaker isn't working, sadly.

It powers up, gives off a low humming noise but the light shines red in off/on/auto until i connect it to my stereo and start playing something, then it lights up green but still no sound.
I've tried all manners of hook-ups.
Then i thought it was just a broken fuse, so i screwed off the backplate and i instantly saw that on the inside both the Filtered and Unfiltered connectors were covered in a brown mass of hardened goo, it looks as though it was fluid at some point because it had formed droplets on the underside of the PCB.
And the fuse was fine, i believe, didn't look like the string had broken.

Can anyone tell me how i should proceed?

Link to the pictures i took.
https://www.dropbox.com/sc/agmd1pxgs9g8ywq/2CZuU3Gi7_

[Deleted User]

Hello,
Welcome to Polk's forum. The brown material is a sealant applied to the RCA sockets to prevent air leaks. Probably the best thing to do would be to remove the sub's grille cloth and take out the screws that go around the circumference of the woofer. Then use a putty knife to carefully loosen the woofer basket from the cabinet. Then pull the woofer from the cabinet and disconnect the two wires that go to the bass amplifier.
Then turn the woofer upside down on a carpeted area and touch one pair of your speaker wires to the woofer's terminals and see if the woofer operates. Just use a small amount of volume and resist the temptation to increase the playing volume if you don't hear anything coming from the woofer. If the woofer works then the problem is with the bass amplifier.
Regards, Ken

embrown057

The brown goo is nothing to be concerned about. It's used to keep the parts from vibrating loose. Unless your very handy with electronics and know how to work on plate amps your going to have to take it to a technician or replace the plate amp. Some plate amp are just not worth repairing but replacing them is a hit/miss endeavor. In other words you may never get that sub to sound as designed with a aftermarket amp. So if your handy and have some test equipment and knowledge you may be able to tackle the problem with a little help. You could go to the DIY website and see what's available there.

LAP87

Hmm, the bass-element/speaker works just fine.
I guess i'll have to take the whole backplate to some electronics-repairshop.
And i yielded no results when i searched on the web for replacements.. hm

I do have multimeter and such, but since i couldn't find any spreadsheets or anything i don't know what i'm looking for.

embrown057

Very seldom can you find schematics for plate amps. The vendors will NOT hand them out to end users but only to authorized repair shops. You would have to do component level trouble-shooting to find the problem. That also would include a BS or EE in electronics/engineering, although not required would be helpful. Living in Sweden I'm sure there's no shortage of highly skilled technicians.

LAP87

Yeah thanks anyways, i'll have to see if i can get someone to take a look at it.. kinda iffs me that i won't be able to use my woofer until it's fixed, if that's even possible...