Pioneer sx-316 subwoofer channel fading

C

Carlo Cupidon

Audiophyte
Hi Guys, I am new to this forum and would like to get some help with fixing my Pioneer Receiver SX-316. Hopefully I am in the right forum. 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
 
C

Carlo Cupidon

Audiophyte
Sounds more like a sub amp issue...
Thanks for the reply. Where should I look around in the amp section? Not sure if I am allowed to put screenshots, but these are the schematics I have been looking at. Perhaps I have missed something out.

I am not too good at measuring voltage while the unit is live. But measured all component offline.

Thank you

1599621001263.png


Pre AMP section
1599621123483.png


1599621423796.png
 
XEagleDriver

XEagleDriver

Audioholic Chief
Thanks for the reply. Where should I look around in the amp section? Not sure if I am allowed to put screenshots, but these are the schematics I have been looking at. Perhaps I have missed something out.

I am not too good at measuring voltage while the unit is live. But measured all component offline.

Thank you

View attachment 39639

Pre AMP section
View attachment 39640

View attachment 39641
Carlo,
Previous response was saying you maybe looking at the wrong piece of equipment. Probably not a receiver problem , but rather a problem in your subwoofer itself.
- What brand and model of sub do you have?
Cheers,
XEagleDriver

Sent from my SM-G975U using Tapatalk
 
TLS Guy

TLS Guy

Seriously, I have no life.
I to would bet that this is a fault in the Sub.

You need to test it with another sub. Or else you need a signal generator and O-scope. Sub amps are basically not serviceable.
 
C

Carlo Cupidon

Audiophyte
Carlo,
Previous response was saying you maybe looking at the wrong piece of equipment. Probably not a receiver problem , but rather a problem in your subwoofer itself.
- What brand and model of sub do you have?
Cheers,
XEagleDriver

Sent from my SM-G975U using Tapatalk
Hi XEagleDriver,
Thank you for your help. The sub is a passive speaker which comes with the receiver, which is a Pioneer Multichannel Receiver SX-316. Can the speaker be faulty drawing a lot of power? I have attached a few pictures of the unit.
Thank you
 

Attachments

lovinthehd

lovinthehd

Audioholic Jedi
Thanks for the reply. Where should I look around in the amp section? Not sure if I am allowed to put screenshots, but these are the schematics I have been looking at. Perhaps I have missed something out.

I am not too good at measuring voltage while the unit is live. But measured all component offline.

Thank you

View attachment 39639

Pre AMP section
View attachment 39640

View attachment 39641
Ah, was thinking vsx receiver models which do not provide an amplified sub channel...I can't help analyze...a repair/service center may be more in order.
 
XEagleDriver

XEagleDriver

Audioholic Chief
Carlo,
I looked up the product and you can replace it with a used model for about $70. Many reviews cited the bad cap problem you spoke of.
- If I was you, I would strongly consider abandoning this system and upgrading to a more robust system. Many of us started with a similar surround-sound-in-a-box system. The improvement potential is very high.
- This forum can help make your new selection cost effective.
XEagleDriver

Sent from my SM-G975U using Tapatalk
 
TLS Guy

TLS Guy

Seriously, I have no life.
Thanks for your help
Carlo,
I'm sorry, I did not look at your post close enough and assumed it was an active sub like most. It sounded like a power amp fault and so assumed wrongly that you were servicing the wrong device.

So, now I have looked at the circuit and indeed I'm sure it is a power amp fault. The sub amp uses and integrated circuit power amp.

This IC is STK412-23OC. I suspect this has failed and has DC offset and that the protection device Q505 is shutting things down and protecting the speaker.

Unfortunately this IC is no longer available. This is pretty typical as ICs usually have one manufacture run and when they are done they are done.

You will need more test equipment than you seem to have to analyze this, and confirm my strong suspicion. Failures in these power amp ICs are common and they are only used in low power units at the lower end of the market.
 
TLS Guy

TLS Guy

Seriously, I have no life.
Carlo,
I'm sorry, I did not look at your post close enough and assumed it was an active sub like most. It sounded like a power amp fault and so assumed wrongly that you were servicing the wrong device.

So, now I have looked at the circuit and indeed I'm sure it is a power amp fault. The sub amp uses and integrated circuit power amp.

This IC is STK412-23OC. I suspect this has failed and has DC offset and that the protection device Q505 is shutting things down and protecting the speaker.

Unfortunately this IC is no longer available. This is pretty typical as ICs usually have one manufacture run and when they are done they are done.

You will need more test equipment than you seem to have to analyze this, and confirm my strong suspicion. Failures in these power amp ICs are common and they are only used in low power units at the lower end of the market.
There are a couple of things you could do to salvage most of your system.

You could lift the power to the sub woofer power amp. Then break the connection to the sub woofer power amp from the sub preamp. Carefully mount an an RCA socket on the back of your unit, connected to the sub preamp output.

Then you could either purchase a powered sub woofer or get an external amp to power your current sub. It would not need to be a powerful amp, those IC power amps are only in the 10 to 20 watt range.
 
C

Carlo Cupidon

Audiophyte
Carlo,
I'm sorry, I did not look at your post close enough and assumed it was an active sub like most. It sounded like a power amp fault and so assumed wrongly that you were servicing the wrong device.

So, now I have looked at the circuit and indeed I'm sure it is a power amp fault. The sub amp uses and integrated circuit power amp.

This IC is STK412-23OC. I suspect this has failed and has DC offset and that the protection device Q505 is shutting things down and protecting the speaker.

Unfortunately this IC is no longer available. This is pretty typical as ICs usually have one manufacture run and when they are done they are done.

You will need more test equipment than you seem to have to analyze this, and confirm my strong suspicion. Failures in these power amp ICs are common and they are only used in low power units at the lower end of the market.
Thank you for looking into it again. I have looked everywhere online but couldn't find anything about this receiver. You must have some secret location. i thought Q505 would be faulty, but now looking at it again it is protection device in the circuit. Thanks for the input
 
C

Carlo Cupidon

Audiophyte
There are a couple of things you could do to salvage most of your system.

You could lift the power to the sub woofer power amp. Then break the connection to the sub woofer power amp from the sub preamp. Carefully mount an an RCA socket on the back of your unit, connected to the sub preamp output.

Then you could either purchase a powered sub woofer or get an external amp to power your current sub. It would not need to be a powerful amp, those IC power amps are only in the 10 to 20 watt range.
I have thought of doing this if I couldn't fix the issue but not sure where to pick up the signal from.

Could I please get a bit of a help from you based on the drawing? Where should I lift the power from and where to pick up the sub preamp output?

Instead of the RCA connection I was thinking to use the existing out via cable. Is that doable or will there be some sort of voltage drop?

Thank you for your help.
 
TLS Guy

TLS Guy

Seriously, I have no life.
I have thought of doing this if I couldn't fix the issue but not sure where to pick up the signal from.

Could I please get a bit of a help from you based on the drawing? Where should I lift the power from and where to pick up the sub preamp output?

Instead of the RCA connection I was thinking to use the existing out via cable. Is that doable or will there be some sort of voltage drop?

Thank you for your help.
It is clear to me now, that you are not experienced enough to carry this out safely. When it becomes clear that there is a safety issue involved I always advise to leave well alone. We don't want to be responsible for injury, or in a worst case a fatality.

If you need to ask the questions you have you NEED TO STAY OUT of that unit.

My advice is to recycle that unit and start from scratch. That unit I am sure is not repairable.
 
C

Carlo Cupidon

Audiophyte
It is clear to me now, that you are not experienced enough to carry this out safely. When it becomes clear that there is a safety issue involved I always advise to leave well alone. We don't want to be responsible for injury, or in a worst case a fatality.

If you need to ask the questions you have you NEED TO STAY OUT of that unit.

My advice is to recycle that unit and start from scratch. That unit I am sure is not repairable.
Thank you for your time.

As mentioned previously, i'm not a champion in electronics but can get by with some help. Tossing the unit and getting a new is not a problem at all, it's just a sentimental piece of equipment that i would like to keep and get it going.

Thank you again
 
mazersteven

mazersteven

Audioholic Warlord
Sorry to see your having issues with your gear.

You could put a nice little 5.1 system together w/ Receiver, Speakers, and Subwoofer for about $1200.
 
newsletter

  • RBHsound.com
  • BlueJeansCable.com
  • SVS Sound Subwoofers
  • Experience the Martin Logan Montis
Top