Solved! Pioneer sx-316 subwoofer channel fading

[Carlo Cupidon]

Hi Guys, I am new to this forum and would like to get some help with fixing my Pioneer Receiver SX-316. I am not a champion in electronics but can get by with some help, and through step by step to hopefully have it resolved. I have been knocking my head around for the past weeks with this subwoofer issue. The receiver starts fine, but after 1 min or 2 it fades away with a light humming or static noise and not proper sound. All the other output works fine. Once you turn the unit off and on, it works fine for the 1st 2 mins then fades away. I have downloaded the service manual and changed all related capacitors for the subwoofer channel thinking it might help but the issue is still here. I have also gone through testing all the resistors and they all seems fine as per the service manual.

I am so stuck now and frustrated, I thought someone could help me please. Thank you

 

[americanaudiophile]

You did try the subwoofer with another source or another subwoofer on the AVR?
By your brief description I would have guessed that the sub has a problem not the AVR.
There's no amp in the AVR for the sub so if the sub out is "fading" the problem won't be a DIY fix. Something is heating up and cutting out. Could even be a circuit board trace.

 

[Carlo Cupidon]

Hi America, thank you for your reply.
I did try with another speaker and the same thing happens. The sub is a passive unit and it does sound that something is heating up and shutting down. Changed a few capacitors and resistirs but same thing. Perhaps it's the IC itself.

I am trying to figure out where could i get the pre amp output from the drawings and have an external amp hooked up to the sub through the existing cable.

 

[americanaudiophile]

My mistake,
That AVR must have been part of a package system since regular AVRs don't have sub amps built in and have a line level sub output.
In that case there is a problem in the AVR built in sub amp not the speaker. That amp may not be compatible with either passive sub you used. Make sure that the sub is 8 ohms.