Can a Sony STR-7055A be dead quiet?

[szdonat]

Hello,

I have this receiver and it has quite high noise floor. A consant hiss coming from mostly the tweeters which isn't affected by any input, volume, balance, tone, etc... .

I read about a few circuits has this thing by factory. Anyone who own one can confirm that, this isn't the case?

I want it to be dead quiet by restoring it, but worth it? The receiver is untouched, completely original.

 

[absolon]

I have one in my workshop that I've used for many years. It is still dead quiet and it is a very nice piece of equipment.

 

[ivandezande]

It’ll always be noisy. I’ve worked on and restored plenty in that series and the noise floor is not great. But that’s true of all early solid state.

 

[szdonat]

It’ll always be noisy. I’ve worked on and restored plenty in that series and the noise floor is not great. But that’s true of all early solid state.

Sad to hear this. I've heard a 6055 which was dead quiet, even with headphones. But this has better sound I think.

 

[spicer]

Hello,

I have this receiver and it has quite high noise floor. A consant hiss coming from mostly the tweeters which isn't affected by any input, volume, balance, tone, etc... .

I read about a few circuits has this thing by factory. Anyone who own one can confirm that, this isn't the case?

I want it to be dead quiet by restoring it, but worth it? The receiver is untouched, completely original.

Something wrong with it. Working correctly you'd be hard pressed to hear anything from it from any driver with volume turned down. I've had a number of them on the bench and at home. They are dead quiet. I will add they are not the easiest unit to work on.

 

[szdonat]

Something wrong with it. Working correctly you'd be hard pressed to hear anything from it from any driver with volume turned down. I've had a number of them on the bench and at home. They are dead quiet. I will add they are not the easiest unit to work on.

It comes from the pre amp, the power amp dead quiet. My guess is something in the power line of the pre amp.

 

[absolon]

I've also got a Sony 6200F at my desk that I've used for 19 years. It required a bit of work on the PS board due to blackleg transistors but since that was done in 2007, it has been dead quiet and still is. Sony made some very high quality receivers in the '70s.

 

[spicer]

It comes from the pre amp, the power amp dead quiet. My guess is something in the power line of the pre amp.

From your first post I assume it is after the volume control which is, most likely, after tone board. You should have the schematic available to break it down. A scope would be very helpful but might not be necessary owing to it being common to both channels. What ever you do do it one channel at a time and take many pictures. If you make a mistake and lose function you'll have a working channel for comparison, looking for errors. Would be nice to have a scope.

 

[szdonat]

From your first post I assume it is after the volume control which is, most likely, after tone board. You should have the schematic available to break it down. A scope would be very helpful but might not be necessary owing to it being common to both channels. What ever you do do it one channel at a time and take many pictures. If you make a mistake and lose function you'll have a working channel for comparison, looking for errors. Would be nice to have a scope.

I have a scope and already did measures, but it seems, the signal levels are too low to see anyting in the pre amp other than scopes noise. I measured -82db in the speaker output in normal case, and -88db with the power amp alone with fft. In other case, i had a weird volume dependent buzz in the right channel. Barely, but I could measure that with a scope and tracked back to the right volume pot. I can't imagine, what can cause this within the pot. It still has this problem too, but at least I know, what causes that.

 

[Semanon]

isn't affected by any input, volume, balance, tone, etc... .

It comes from the pre amp, the power amp dead quiet. My guess is something in the power line of the pre amp.

This confuses me. If it is not affected by the volume control, it’s most likely the amp. You should be able to check this by separating the amp and the pre with the switch.

Lots of things could do this. I guess making the amp quiet would be the first step, then work your way through the tone board and flat amp, then the phono pre. Of course this is after a good cleaning and lube.

 

[szdonat]

This confuses me. If it is not affected by the volume control, it’s most likely the amp. You should be able to check this by separating the amp and the pre with the switch.

Lots of things could do this. I guess making the amp quiet would be the first step, then work your way through the tone board and flat amp, then the phono pre. Of course this is after a good cleaning and lube.

I separated, that's why I know, it's the pre amp alone. And thought to the pre amp power line, because nothing changes it. Yes, the cleaning would be a very good start...

 

[ET16]

I've also got a Sony 6200F at my desk that I've used for 19 years. It required a bit of work on the PS board due to blackleg transistors but since that was done in 2007, it has been dead quiet and still is. Sony made some very high quality receivers in the '70s.

What are the "blackleg" transistors?

 

[absolon]

What are the "blackleg" transistors?

The legs turn black as a consequence of corrosion and eventually rot through breaking contact with the board. In my case, I cut back the corroded legs to good metal and reinstalled them. Worked a charm, that was back around 2007.

 

[ET16]

The legs turn black as a consequence of corrosion and eventually rot through breaking contact with the board. In my case, I cut back the corroded legs to good metal and reinstalled them. Worked a charm, that was back around 2007.

Good to know.