Luxman L-116A left channel buzz

[Hepokatti]

Hey.

I got this amp, and it has a small problem that bugs me, but it doesn't affect listening;

There is a very faint buzzing sound in the left channel which is barely audible through both headphones and speakers. I can only hear it when putting my ear very close to the speaker, but its there nevertheless. The sound doesn't get louder as I put more volume.

What this could be? I have checked the caps and they are intact, I have cleaned the potentiometers, I have tried different sockets in my apartment (I don't think its a grounding problem - at least not a normal one. And I don't have this problem with other amplifiers.) etc.

Also the PSU of the amp is buzzing when listened closely.

Some pictures (newest post): http://cheapanaloguehifi.blogspot.fi/

Any ideas?

[rhomanski]

Are you saying the PSU is buzzing by itself? That could mean the coil of the main transformer has come loose. Try tightening the bolts and nuts that hold it together. If that doesn't help then you can try to disassemble it and try to reglue it. Best thing to use for that is corona dope. If the two aren't stabilized then the coil will move because of the magnetic field and chatter against the iron core. You'll hear a sixty or fifty cycle buzz.

The hum could be a capacitor going bad and not filtering the AC signal as well as it once did. Since it's in only one channel the problem will be a cap in that channel. I rebuilt a preamp recently that had a loud hum in both channels and found one of the new capacitors I put in was bad. After replacing it again I still had a hum in only one channel. I waited and that capacitor finally reformed itself and now the hum is gone. A new capacitor sometimes needs to be run a while to operate properly. Same for a unit that has been put up for a long time.

Regards,

Ron.

[Hepokatti]

Are you saying the PSU is buzzing by itself?

Yup! Thanks for the tips.

The hum could be a capacitor going bad and not filtering the AC signal as well as it once did. Since it's in only one channel the problem will be a cap in that channel. I rebuilt a preamp recently that had a loud hum in both channels and found one of the new capacitors I put in was bad. After replacing it again I still had a hum in only one channel. I waited and that capacitor finally reformed itself and now the hum is gone. A new capacitor sometimes needs to be run a while to operate properly. Same for a unit that has been put up for a long time.

Alrighty. I suspected this, but then I was told in another forum that a "tired" (For the lack of a better term, since the caps are not exactly broken.) capacitor wouldn't do something so little - it will do a noticeable hum. Maybe they were just guessing, as your suspicion made more sense in the first place.

http://1.bp.blogspot.com/-1S5WQngFEXI/T ... +cap+3.jpg

Is the gooey stuff at the bottom of the capacitors glue, or could it be leaking electrolyte?

Thanks again Ron!

[rhomanski]

I have never seen a Luxman, let alone worked on one. Other manufacturers used glue to hold the large capacitors on the board while it was soldered. Luxman may have as well. The glue I have seen is beige in color when still moist and turns brown after it's cooked by the heat in a unit. From your picture, I would say that's glue.

I would also say, it looks old enough to be ready for a recap. It's not absolutely necessary but would be good to do. If you can solder, I might be able to help if you wish. All of mine are from the mid to late seventies and I can tell you it makes a big difference. I have no scientific evidence but I suspect the charge rate may slow down as they age, causing the sound to get muddy. After recapping all my gear I have noticed a huge difference in the clarity of the music. When I bought it my gear sounded good. After recapping, they sound beautiful.

Regards,

Ron.

[donpipo]

I've been taken to your post by a Google search, but I'd like to resurrect this thread to know whether your have made some progress or someone could be of any help regarding this issue...

Just to say that I have the exact same issue with the same amp.
Your words are correct: "a faint buzz in the left channel you can hear with headphones or by listening closely to the speakers".
The volume control doesn't affect it, however tone controls have effect on its tonality.

The noise character is clearly is transformer buzz, like the one you can hear coming from a halogen lamp foot slider, for instance.

So, it's clearly coming from the amplifier part, since the tone controls are located on the negative feedback loop. And only on the left channel.

I've recapped all the electrolytics even the big filtering ones and the faint buzz is still there
I've tried for hours to find where the problem is coming from, testing all components, resolder everything, exchanging suspicious parts between channels, tightening the transformer bolts, pulling the transformer out of the chassis (since it's close to the left channel circuitry on the PCB)... Nothing changed.

I've abandoned since a while but interestingly, I've found some posts like yours regarding the same issue.
Here are my posts (in French ) regarding the still-not-solved issue:
http://www.abcelectronique.com/forum/sh ... hp?t=64039
http://www.audiovintage.fr/leforum/view ... =11&t=2075
I've put myself again in it since I have to replace the volume potentiometer.

That said, every people who came to my topics said they gave up, even helped with skills of a skilled professional technician
I've contacted even OP of old topics saying "buzz on the left channel on my L-116A". Nobody has never found the origin of the problem.
People always describe the same problem and say that it has appeared over time.

So, here is my small and humble contribution...
Hope someone could help us!

Alex.