Windy noise in R-900

Aspen

Active Member
It seems my recently repaired R-900 (new right STK, few burnt resistors) has a new issue. The right channel has a noise that sounds like wind blowing. It's only on the right side and volume has no effect. At zero volume it is about 5 or 6db of noise vs the left which is dead quiet. It can be heard in the headphones on right side only. It was louder when I first noticed it and made the music on the right sound distorted with no bass.
I powered off for 10 minutes and it was inaudible when I switched on. Came back after 20 minutes or so. No effect if I change input sources, switch the coupler, or any other control.
Any ideas?:scratch2:
Bad capacitor?
Cold solder?

All input kindly appreciated. I was planning to get the tuner aligned, maybe I will have the tech go through it and recap some of it.
 
Most "wind" sounds I've found that in gear is a bad transistor.
Hopefully someone with experience with that model and familiar with the parts compliment can narrow the target down a bit.
 
Most "wind" sounds I've found that in gear is a bad transistor.
Hopefully someone with experience with that model and familiar with the parts compliment can narrow the target down a bit.

Thats what I was thinking..transistor noise.
 
Thanks guys. I searched some threads here and bad transistor seems to be the usually culprit.
 
Thanks guys. I searched some threads here and bad transistor seems to be the usually culprit.

Where did the STK come from? Most likely suspect.
 
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Hi,
The STK came from the shop that did the repair. A long time, 3 decades, Yamaha authorized shop. He happened to have both an amp and a voltage amp in stock, but I only needed the amp. STK1070II. I assume it was old stock, but I noticed that it is cosmetically different from the left side; maybe a later Yamaha issue, Sanyo generic or a reproduction.
I used the receiver every day for about six weeks and all was good. I then left the unit powered up at idle for a day (at the suggestion of an audio guy who claimed it would be better to leave it at idle then to switch on and off). That's when the noise started.
The unit is in for repair at a different shop because I wished to have the FM tuner aligned and the first shop doesn't do those. Only parts warranty is still in effect, not labour and since I was billed $40 for the STK there wasn't much to be gained. If the STK turns out to be the problem I may be stuck and need to return it to the first shop or give up on it. We will see.

Are there any reliable sources of the old STK's? I have seen some for sale from multiple suppliers but don't know if the parts are good quality.

I figured that since the noise level did not change when I turned up the volume that it was not an amp issue. Also it was still noisy with the pre-main coupler switched off. So I was surmising that the amp section was OK and that my problem is in the front end?
 
Also it was still noisy with the pre-main coupler switched off.
If it was noisy when the pre-amp was disconnected from the power amp.Its definitely the power amp thats noisy.
 
I meant, the noise continued in the headphones with pre main coupler off.
Makes no difference ! Head phones or loud speakers both get there signal from the power amp, not the pre-amp. Look over the schematic . Theres a free service manual at HiFiEngine.com.
 
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I have the schematic, but it might as well be in Dutch, I can't read that as I am no tech.

I hope it's not the "new" STK then.

Thanks.
 
I have the schematic, but it might as well be in Dutch, I can't read that as I am no tech.

I hope it's not the "new" STK then.

Thanks.

Can you make a video or audio track of the noise. "Windy noise" is a rather vague description. Windy as in a spring zeypher or tropical hurricane.:D

Its probably going to be one of the STK's is noisy.
 
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The unit is in the shop now so I can't record it.
The noise sounds like someone gently blowing into a microphone. When I first noticed it was very bad, easily heard and made the right side sound distorted with no bass when music was playing. After I powered off and back on 1/2 hour later it was much quieter and not noticeable when playing a source.
I measured it at each speaker about 2" in front of the woofer when it was fairly quiet, with no source the left channel measures about 22 dB on my cell phone SPL app, the right with the noise measured 27dB. The faintness noise can be heard on the left as well, just slightly more audible than dead quiet. If I turned up the volume it didn't get louder, I just get some crosstalk from the FM tuner which was there before this issue.
 
Update,
I got the receiver back from service. The tech ran it for a week and he couldn't hear the noise I had described and it never went completely bad on the right channel. Sure enough I got it home and hooked up and I can still hear the noise. Granted it is very faint, but it is there.
He did align the tuner section for me, so that was good. Pulls in strongly and right away with no warm up period required. Quartz lock works on the first try.
I guess it will stay the way it is until it A) gets worse or B) go for a whole recap or C)dies completely.
 
I have got funky feed back on tone controls before on R series. Does setting them flat cause it to go away. My try deoxit of pots or leaving tones flat one at a time to find if culprit. I have a R900 in shop now I killed running too low of impedance speakers. The R700 an R900 have warm tube sound. Opposed to neutral R1000 and R2000. But they are all good.
 
I did give it a thorough cleaning with Deoxit at least twice, vacuumed, air blast and alcohol swabs of the boards. The volume and input sector cleaned up well. All the controls are quiet now.
I don't recall the tone controls changing my issue, but I will check it out to be sure. Thanks.
 
Ok, I tried a number of things. The faint noise is only on the right through the speaker, mostly treble. Not present in head phones. No control has any effect. My theory is that the replacement STK amp on the right has a floor level of noise. It is different and doesn't have "Yamaha" printed on it so may be an inferior chip.
Oh well.
I guess someday I could swap left and right to see if the noise moves.
 
Have you tried all RCA connections. What inputs provide noise? All or TT? Do you have a florescent lamp or Fan nearby? Something is differebt betwee your home and repair shop. Thus try to rule those out.
 
Have you tried all RCA connections. What inputs provide noise? All or TT? Do you have a florescent lamp or Fan nearby? Something is differebt betwee your home and repair shop. Thus try to rule those out.

Yes all RCA and inputs. Can't tell with the tuner because it is always on a station. The phone input is a whole lot of noisy, but it is more a hum
in both channels equally and gets louder with the volume. I don't have a tt so it doesn't matter to me. I suspect there are out of spec parts in that section.
There is indeed some RF in the house because I tried a cheap 25ft cable from my laptop and it buzzes like mad when connected to the receiver. There is a dimmer switch in the room that is noisy too, but doesn't affect this issue. The furnace is below about 20 feet away which may be my rf source.
I think it made the noise at the shop too but it is faint enough that the tech couldn't hear it. I am just being very fussy.
It is weird though, I would think that turning up the volume would make it louder but it doesn't.
 
Yes all RCA and inputs. Can't tell with the tuner because it is always on a station. The phone input is a whole lot of noisy, but it is more a hum
in both channels equally and gets louder with the volume. I don't have a tt so it doesn't matter to me. I suspect there are out of spec parts in that section.
There is indeed some RF in the house because I tried a cheap 25ft cable from my laptop and it buzzes like mad when connected to the receiver. There is a dimmer switch in the room that is noisy too, but doesn't affect this issue. The furnace is below about 20 feet away which may be my rf source.
I think it made the noise at the shop too but it is faint enough that the tech couldn't hear it. I am just being very fussy.
It is weird though, I would think that turning up the volume would make it louder but it doesn't.

I can't recall since my R900 is in the shop. But can you decouple the Preamp from the amp on R900 with a switch like the R1000 and R2000? That would isolate the section with wind. Also if spatial expander has switch. Switch it out and check. Even at dial to zero it will massage the signal on the TOTL receiver.

Without RCA on TT should not hum unless you have power wire going in front of jacks. Run power and signal wires separated.
 
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