Heat causing buzzing?

[mud3342]

This is a question about a buzzing that my receiver makes that I've been ignoring for a long time. I've done a moderate amount of looking for a solution from other threads here, and there are ones about buzzing, but I don't think they apply to my problem, and I need something specific.
I have a SONY STR-K750P which sits on a shelf, and I think theres plenty of breathing space around it, and about 2 inches above it. I am pretty sure the problem causing the buzzing is coming from there. What happens is when I have it on for around an hour, regardless of input, there is a very audible buzz, that come from the speakers, which is about the same level regardless of volume. Before that time it sounds fine though. I only recently realized from putting my hand over it during the buzzing that the receiver it is very warm. After I leave it off for about 30 minutes, and it cools down, I can turn it on and the buzzing is gone until its been on long enough.
In one thread I read something about buzzing being caused by the power outlet, so the other day I unplugged it from the wall and into another outlet on the other side of the room, testing under the same amount of time, but the same buzzing happened, so I'm doubtful its the power.
I'd like to know what I should do or get to make this stop, please help, and thanks.

 

[Exit]

It sounds to me like a cooling fan kicking in after the unit warms up enough. I have a small six-pack refridgerator where the cooling fan makes a buzzing noise. I clean the dust out and spray WD40 in the fan assembly and it quits making noise for about 6 months. You may just need to get a can of electronics/computer spray dust cleaner and clean out the fan and circuit boards. Just my best guess, but it is a cheap fix to try. I wouldn't use WD40 in a receiver though. If it is more than dust, the fan may need replacing. The fan is the only mechanical moving part I can think of thats ini a receiver that would make a noise.

 

[Midcow2]

... What happens is when I have it on for around an hour, regardless of input, there is a very audible buzz, that come from the speakers, which is about the same level regardless of volume.

How old is the AVR? Are you willing to have it serviced? It could be a capacitor in the power supply on the verge of going bad.

 

[mud3342]

How old is the AVR? Are you willing to have it serviced? It could be a capacitor in the power supply on the verge of going bad.

It's about 6 or 7 years old. And I would be willing if its the only way to fix it, and I knew for sure theres a good chance, cause I pretty much use it every day.

To Exit: I'm not able to open it up or do any of that kind of stuff. Also, I don't think the buzzing comes from any fan in there, because like I said, the buzzing is heard through the speakers, not out of the receiver, thats always silent. I was sure it isn't the speakers, however, cause they are quiet if it hasn't been on that long.

 

[TLS Guy]

It sounds to me like a cooling fan kicking in after the unit warms up enough. I have a small six-pack refridgerator where the cooling fan makes a buzzing noise. I clean the dust out and spray WD40 in the fan assembly and it quits making noise for about 6 months. You may just need to get a can of electronics/computer spray dust cleaner and clean out the fan and circuit boards. Just my best guess, but it is a cheap fix to try. I wouldn't use WD40 in a receiver though. If it is more than dust, the fan may need replacing. The fan is the only mechanical moving part I can think of thats ini a receiver that would make a noise.

He says the buzz comes from the speakers and not the unit. It is not a fan. This unit's power supply is going down and it is loosing smoothing as it heats up. Continuing to use the unit in this condition will almost certainly result in further damage.

With a unit of this age, you will have to set a sensible limit on service costs.
Power supplies in modern equipment can be very complex.

 

[mud3342]

With a unit of this age, you will have to set a sensible limit on service costs.
Power supplies in modern equipment can be very complex.

I haven't ever had something serviced before, could somebody give me an idea of what to do? Does Sony do it themselves, or do I take it somewhere? I'm not the one that handles costs, but all I know is I wouldn't want to spend more than it would cost to just replace it...

Something I forgot to mention, if it makes a difference, is that alot of the time I will use the headphone jack with it (which is why the problem is something I always am bugged by but easily overlook), and buzzing doesn't come from the headphones, it still comes from the speakers with the same amount of time.

 

[TLS Guy]

I haven't ever had something serviced before, could somebody give me an idea of what to do? Does Sony do it themselves, or do I take it somewhere? I'm not the one that handles costs, but all I know is I wouldn't want to spend more than it would cost to just replace it...

Something I forgot to mention, if it makes a difference, is that alot of the time I will use the headphone jack with it (which is why the problem is something I always am bugged by but easily overlook), and buzzing doesn't come from the headphones, it still comes from the speakers with the same amount of time.

Your last piece of information tells is the problem is in the high voltage supply to the output devices.

You need to look in your local yellow pages and look for electronic service shops. Ask them if they repair Sony products. Get an estimate. If the fault is unusual, the cost of the estimate may be almost the cost of the repair. Chances are an experienced tech has seen the fault before. Identical models have a habit of failing in identical ways. If yours has a problem this unit is known for, that makes it easier and cheaper.

After you get it back, you need more ventilation. The unit should not get that hot. Heat = increased rate of failure.

 

[mtrycrafts]

It's about 6 or 7 years old. And I would be willing if its the only way to fix it, and I knew for sure theres a good chance, cause I pretty much use it every day.

To Exit: I'm not able to open it up or do any of that kind of stuff. Also, I don't think the buzzing comes from any fan in there, because like I said, the buzzing is heard through the speakers, not out of the receiver, thats always silent. I was sure it isn't the speakers, however, cause they are quiet if it hasn't been on that long.

One way to test if it is the speakers causing this hum is to turn the volume down for a while and back up and see if the hum is there and a second experiment is when the volume is down or if you have a mute feature to disconnect the speakers for some time while the unit is on so it won't cool off, reconnect the speakers and see if it hums. If it does, your receiver has some issues.

 

[TLS Guy]

One way to test if it is the speakers causing this hum is to turn the volume down for a while and back up and see if the hum is there and a second experiment is when the volume is down or if you have a mute feature to disconnect the speakers for some time while the unit is on so it won't cool off, reconnect the speakers and see if it hums. If it does, your receiver has some issues.

Speakers can't cause hum, only reproduce it. There is no buzz in the headphone socket, so there has to be problems with the power to the amp section.