Sony Wireless Headphones MDR-RF820

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

I got my caps today. I will take some pictures of the caps for you guys to see how they look like. They truly seem to be genuine Rubycons. I recapped the transmitter base PCB, but unfortunatelly, the problem is still present. Still occasional hiss sounds appear. But there is a slight difference now, they do not get worse when moving around the room. I guess these headphones started exerting some FCC directed behaviour, causing an undesired operation.

Anyway, I only ordered replacement caps for non-Rubycon caps, but maybe some of the Rubycons went bad. Maybe it's not the caps at all. I also recorded the hissing sound with a microphone, but I don't know if it is possible to attach a file type other than image.
I will post some images for you to see the recapping results, but I am getting tired of this malfunction. The recapping went smoothly, but the results were and still are disappointing. I have a bigger fish to fry now, and that is the ongoing PSU problem.

[momaka]

Re: Sony Wireless Headphones MDR-RF820

Well, I suggested this several posts back, but I didn't get an answer from you...
Did you try swapping the power supplies/adapters that power these stations? What about the audio cables between the station and whatever it is getting its signal from?

There is also a BA3308F pre-amplifier IC on the transmitter board. You should verify that it works by inputing a signal into the base and seeing if you get anything on it's output pins (pins 1 and 7, that is).

There are other ICs, but I can't see their numbers. I doubt they would have failed, though, so let's leave those alone for now and focus on the items above.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

Momaka, thanks for your your reply. I did test my base at my sister's, when I wrote about comparing the operation between mine and her headphones. It meant that I connected my base to her adaptor (I didn't bring my adaptor and/or cables because she also has the same model and everything was compatible). My headphones did not hiss when receiving from her base, but her headphones did hiss when receiving from my base - both bases were connected to her adaptor one at a time.
Also, I added that additional 16V220uF capacitor near the DC plug on my base's PCB, but I guess it didn't make too much of a difference. I will include these pictures as soon as I get home and grab some time to do it.

[Moreno83]

Re: Sony Wireless Headphones MDR-RF820

" My headphones did not hiss when receiving from her base, but her headphones did hiss when receiving from my base - both bases were connected to her adaptor one at a time. "

EDIT: I Read to late that you already know the problem is coming from the base.

[momaka]

Re: Sony Wireless Headphones MDR-RF820

Momaka, thanks for your your reply. I did test my base at my sister's, when I wrote about comparing the operation between mine and her headphones. It meant that I connected my base to her adaptor (I didn't bring my adaptor and/or cables because she also has the same model and everything was compatible). My headphones did not hiss when receiving from her base, but her headphones did hiss when receiving from my base - both bases were connected to her adaptor one at a time.

Ah okay, good! That means you isolated the problem to not being the power adapter or audio cable too.

With that said, just to make sure the issue is not the other caps you didn't change... get a hair dryer or a heat gun and heat the entire transmitter base PCB well - no so hot to burn yourself, but close. Then see if that makes a difference. If it does and the transmitter works, then you either have bad caps or a bad solder joint somewhere.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

Here are the replacement caps, the ones I got from egekecu.

I am going to try the hairdryer trick now as it will be an easy access now that the base is apart.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

Nope, heating with the hairdryer had no difference whatsoever...

Here I have attached the hiss sample that I have recorderd by putting a microphone directly against one of the earpads and turning the headphones on, since the hissing is heard identically on both left and right channel. These "spikes" of hiss occur intermitently, sometimes in pulses, sometimes in intervals, and their duration varies - but are quite annoying when listening to music.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

@Momaka

You suggested to check the input. I am not sure what you were referring to, but if you meant the sound input, then yes, there is one. The base turns itself off and stops transmistting automatically if there is no sound input for about 4 minutes. As soon as it senses the sound signal again, it turns itself back on and starts transmitting again. This is a product feature.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

Is the included "hiss record" of any help?

[Moreno83]

Re: Sony Wireless Headphones MDR-RF820

Well there is not much else on the board besides caps and some small ic's.

In this case i would mark the potmeter as it is right now and slightly change it while playing some sound like music.....
Maybe the frequency changed a little.

[momaka]

Re: Sony Wireless Headphones MDR-RF820

Here I have attached the hiss sample that I have recorderd by putting a microphone directly against one of the earpads and turning the headphones on, since the hissing is heard identically on both left and right channel. These "spikes" of hiss occur intermitently, sometimes in pulses, sometimes in intervals, and their duration varies - but are quite annoying when listening to music.

Interesting.

So the transmitter is sort-of working then? As in, you can listen to music and whatnot, but only that there is also a hissing noise on top?

The hissing sounds almost like some high-power computer/digital noise is getting through. If you are listening to music, let's say, does the audio go out when you hear the hiss or does it continue with the music?

You suggested to check the input. I am not sure what you were referring to, but if you meant the sound input, then yes, there is one.

No, I meant trace the audio input on the transmitter board and see if it goes to the BA3308F pre-amplifier IC. If it does, then also see if the audio you get out of the BA3308F IC is the same or noisy.

Is the included "hiss record" of any help?

Yes. I think we need to define the issue a little better. Try playing a short music sample through the headphones and record that. Also mention/upload the short music sample you used so we can compare.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

@Momaka, thanks. OK, here it is:

The hiss is present whether I play something or not. If I tune the headphones to pick a local radio station, the hiss disappears. As soon as I tune them to receive from the transmitter, the hiss and fuzziness appear. Just like in the recording, if nothing is played and the base is on, that hissing is all you can hear. When music is played, the hiss is also present but is therefore masked by the music sounds. If in the music there is a more slient part, pauses, beats and alike, the hiss is heard more prominently as there is less of music stuff to mask it. Also, if I turn the volume knob up on the headphones, the hiss also becomes louder. Nothing gets cut off, it's just as if the hiss somehow became incorporated into the radio waves sent from the base. I can hear all the tones when listening to anything, its just that there is this random and annoying hiss present all the time.

As for the IC you mentioned, I can try tracing the leads on the PCB, but if tracing would require the use of some specific equipment, I don't have any. If it doesn't, please direct me on how to trace that.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

OK, here is the sample with normal sound (original) and the one through the headphones (recorded):

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

As you can hear, at the very beginning of the recording, there is a rather long hiss sound on top of the background hiss. It appears and re-appears completely arbitrarily throughout the listening to anything, but is always to some degree present. When listening to a beaty, more filled music, it is not so noticable because it gets mixed with the music sounds. But on pieces such as the recorded ones with silent parts and pauses and things alike, it is even more annoynig.

The computer and the headphones base are at the very same place where they have always been from the first installation. I also have a Mackie CR4 monitors and so I thought maybe the base is picking something from the PC motherboard. So I tried the monitors' headphones jack - completely the same thing.
No hardware or spatial changes occuered in the meantime, so the problem started really all of a sudden.

[Moreno83]

Re: Sony Wireless Headphones MDR-RF820

What does that little potmeter do?

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

What does that little potmeter do?

I don't know. I didn't touch that. There is the same one in the headset. It's probably tuning something.

[Moreno83]

Re: Sony Wireless Headphones MDR-RF820

You could just play a sound and use the potmeter and see if it changes anything. For example when you are listening to the radio in your car and the signal is bad. Add a little MHZ up and signal is good again.....

Maybe the hiss is bad frequency

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

I am not quite sure what you think I might achieve by fiddling with that potmeter. The base already has 3 channels selector switch, which are - according to its user manual - ranging in 0.5Hz respectively. The headset has a tune wheel, and no matter which of the three channels is selected, the hiss tunes itself within the signal. Not knowing exactly what that pot does might prevent me from turning the base into its original state. I don't know how sensitive the changes would be, which might make it difficult to return to the exact original state even if I marked the pot position to begin with. Maybe a bit more reassuring information could help.

[momaka]

Re: Sony Wireless Headphones MDR-RF820

As you can hear, at the very beginning of the recording, there is a rather long hiss sound on top of the background hiss. It appears and re-appears completely arbitrarily throughout the listening to anything, but is always to some degree present. When listening to a beaty, more filled music, it is not so noticable because it gets mixed with the music sounds. But on pieces such as the recorded ones with silent parts and pauses and things alike, it is even more annoynig.

Well, thanks for providing the sample. It really gives a lot more insight to what is going on.

Unfortunately, I'm not sure what could cause that slight hiss/noise. It is not constant, so I don't think it's a drifting tunning frequency issue. (Though if someone knows more about radios, please correct me if I am wrong). That said, I imagine a headset like that probably uses a PLL IC to do the FM modulation. Thus, if there is a bad component, probably nothing will work. Most likely, there might be a resistor or a capacitor (non-electrolytic too) somewhere that is drifting only slightly in value due to age, and thus causing the PLL IC to misbehave.

The computer and the headphones base are at the very same place where they have always been from the first installation. I also have a Mackie CR4 monitors and so I thought maybe the base is picking something from the PC motherboard. So I tried the monitors' headphones jack - completely the same thing.
No hardware or spatial changes occuered in the meantime, so the problem started really all of a sudden.

And you also tested at your sister's place, which eliminates all of the above things as possible causes.

Not knowing exactly what that pot does might prevent me from turning the base into its original state. I don't know how sensitive the changes would be, which might make it difficult to return to the exact original state even if I marked the pot position to begin with. Maybe a bit more reassuring information could help.

I agree.
Don't touch it yet if you don't know what it does.

First try to trace to what IC it is connected to. Then get the datasheet for that IC, find what pins the pot connects to, and try to see what its function could be.

I know that is much easier said than done, of course. But with a little bit of patience, you should be able to trace it. Post back what you find, though, so we can try to help you with finding IC datasheets and trying to understand what the pot does.

If bad comes to worse, then we can try to play with the potentiometer. But before doing any of that, do make sure to mark its original position so that we can return it back to what it was. I doubt it would be that sensitive that you can't get it back to what it is originally - that would be a bad design and could make the headset/base not work even from a simple drop, as that can often cause the pots to vary a little.

As for the IC you mentioned, I can try tracing the leads on the PCB, but if tracing would require the use of some specific equipment, I don't have any. If it doesn't, please direct me on how to trace that.

Specific equipment required: a pair of good eyes and a multimeter with resistance test function (set to lowest resistance scale, if using a manual meter). That's it. No other fancy stuff needed.

[UserXP]

Re: Sony Wireless Headphones MDR-RF820

@momaka

I haven't been in for a while, a bunch of stuff came out to be concluded.
Anyway, I recently got an AN8008 multimeter, it has the required measurement capability with auto mode. So now we can test that signal, you'll just have to direct me on what to do exactly.

While playing with the multimeter, I checked the removed caps from the PCB board, the Lelons and Sam Youngs... And according to the multimeter, their capacitance was almost identical to the rated values. So maybe nothing was wrong with them to begin with and I replaced those for nothing. The culprit for the noise must be somehere else.