Subwoofer has stopped working - help

PiKe

PiKe

PiKe

Caporegime
Joined
18 Oct 2002
Posts
25,287
Location
Lake District
I first noticed a week or so ago that my sound was a little tinny and found that the subwoofer wasn't working, I turned it off and then back on it was fine but the issue has occured again and turning it off and on isn't fixing it this time.

I took the phono cable out the amp ends and touched the end (which should cause feedback to the sub I've read) but it's deafly silent.

What is in an active sub that can go wrong?

I have the Pioneer SHS100 speaker set with a Pioneer VSX-920
 
Taken the subwoofer apart, I'm missing 32v it seems, I have 3.3v and 5v which presumably drives the led and standby mode circuits.

I will need to take the power board out once it's discharged and see if I can trace where the 32v comes from.
 
Can't figure it out, I can only trace continuity so far, is there anyone that I can send the board to in order for it to be fixed?
 
It's worth having a look at the big capacitor(s) on the amp board. They can go faulty gradually. Usually it's swelling due to being too close to a heat sink, but sometimes it hard to spot the symptom.

As long as the cap isn't completely dead then there's a little trick with a hair drying which can help with fault-finding.

Switch off the sub. Warm the capacitors. Try switching on. If you get the sub come back to life then change the caps. Go for the exact same voltage. Always 'up' the microFarad rating if you can't find an exact match, but never go smaller. If there's an opportunity to choose a higher temperature value then take it. Most caps used in circuits are 85 degree C for cost reasons. There are 105 deg C caps too. Choose one of those.
 
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