Try to fix my sub but got stuck. Advice?

[TheGimp]

If that voltage is when it is disconnected from the amp, then it is normal. The adapter has a high output resistance, which when under load drops the voltage down to the specified 18VDC.

If that measurement is with the amp connected and running, then it is probably too high.

 

[flux55]

Thanks Gimp. That was a no-load reading from the power supply. I'll check that off the list of possible causing problems. Will now focus on those capacitors as the probable problem.

 

[nigelwright7557]

Be careful if you fix your amp before checking the speaker.
Sometimes a blown amp will fry the voice coil.
Then applying power from your fixed amp will blow it again !

 

[flux55]

Thanks Nigel for this extra warning. I'll compare the Ω readings of each speaker and check for shorts.

 

[flux55]

Overheating & Hum FIXED

Thanks to PSHITNIS I fixed this problem for ~$5. First I like to say I know very little regarding electronics. But I'm good at following instructions. Ordered those capacitors from ebay. Over 3-weeks shipping time from Hong Kong. I'm on a tight budget, so this was worthwhile. Kudos to pshitnis.