[samosali]

In first amplifier the basses had a strong buzzing noise. The professional repaired it and it worked for several months. Then the right front channel had a noise and I tried to repair it on my own. i did not succeed therefore I bought a remanufactured amplifier on e-bay from USA. It worked for about 5 days and then all channels had strong buzzing noise.

Only to check what is going on, I replaced it with the old one (with one channel damaged) and it worked fine on 6 channels. So my conclusion was that something is wrong with the amplifier from e-bay. The professional repaired my first amplifier (with damaged channel) with parts from amplifier from e-bay. the "Frankenstein amplifier" worked about 10 minutes and here is the strong buzzing on all channels again.

Now i think there must be something wrong with other components. Is it possible or I just do not have a luck with amplifier repair/purchase? So far I spent 500 EUR on all this and I really want to finish this story. I think that my only option is to replace everything (I would like to keep speakers and wires) ... but what if something is wrong with wires or speakers? thanks for your comments.

 

[samosali]

One hour ago I went to the car and I disconnected the CD exchanger/player. then i reconnected it and all is well now.

I do not know if disconnecting the CD player had any influence or not ... the only sure fact is that the amplifier is not burned at all. And most probably the remanufactured amplifier was not toasted as well.

So now the question is slightly different: what can cause so strong buzzing noise on all speakers? can it be CD player itself?

 

[Merc-S600]

Hi Champ
When you reinstall'd the AMP the 1st Time before you hear'd the Noises ,did you make sure that everything was Connected Perfectly at the TUNER in the Boot ,near the AMP that little Box .?
I cant exactly remember ,when i did mine ,but i connected 1 Wire wrong and it made a strange Noise ,I thing it was the Brown one on the Tuner ,it wont make Smoke but makes Noises ,like a high Pitch Sound ,its verry easy to get confused with the Wires at that Box if no Picture or Drawing was made before Disconnecting everything .
Well hopefully you solved the Problem already ,thats why the Champion on the Top ,LOL.

Ciao

 

[samosali]

Hi Night Rider

thanks for your reply. Your idea is not bad however I did not touch anything else except amplifier's connector. But I certainly will check all wires and all boxes near amplifier.

The sound which came on was extremely loud ... like volume knob is almost to the far end and "music" is buzzing only.

I think there are two boxes near amplifier. One is just under the amplifier (not fixed on a car). Another one is slightly more towards the end of the vehicle and a little bit lower, it is fixed on a car and it is slightly bigger than the first one. I think the problem lies in CD player, wires, or in on of the two mentioned boxes. Is here any logic?

(night rider: because you answered when I was asleep).

 

[Merc-S600]

Hi Night Rider

or in on of the two mentioned boxes. Is here any logic?

(night rider: because you answered when I was asleep).

LooooL,Your Car is or should have the same setup like mine ( 93 S500 ,Late July Series ,just after the Badge Switch ) Anyway , I dont recall having seen an additional Smaller Box anywhere near the Amp or Tuner at the Rear .
I imagine that Sound and i'm more than sure that i have hear'd it during my New Radio Installation ,it was a crossed Wire ,even a Speakerwire is inaf to make that Sound as they go trough the Amp wich Ampliefies this Sound even more ,just check all the Wires and if you removed the Radio inside the Car ,maybe the Problem could be there too .
When renewing the AMP it is Recommended to also renew the Tuner ,Both together AMP & Tuner .
Is your System all BOSE' ?
Whats the Weather like over there in Slovenia ,here its Boiling Hot ,tomorowe 42 degrees ,WOW .

 

[Merc-S600]

Coming to think about it , Where did you send the AMP too, to do the Rebuild .Leo the Guy in the US, he's done mine & is absolutely working 100% ,Beautifull Sound on all Channels (Left-Right-back-Front-Up & Down ,Musik everywhere ,even in the Petrol Tank,Engine ,Tyres etc. ,LoL. ) .
Leo is cheap he fixes them & Resells some that he has already fixed on Ebay for 300 Dollars i think or around that figure .
I Paid around the 180/90 US Dollars plus Postage ,took 1 Week and i got it Back ,verry fast Service .I cant even say that he send me a different AMP Back that he fixed earlier ,I put a Secret Mark on my AMP before i send it ,so he is honest too .
Ciao :thumbsup:

 

[samosali]

Thanks for your input, I consider crossed or damaged wires seriously now. My car is pretty much in original condition, but because the PO was an electrician we can all imagine that this part of the car is the worse (ironically!). It seems that he put something inside which is not original. The box is ca 10 x 25 x 4 cm and it has two round connectors. Yes my system is BOSE but the CD player is for 6 CDs – Alpine (do not remember exact denotation on it but I could swear that it does not have a MB star on it).

The weather is normal for winter time, we have ca. half of meter (20 inches) of snow and temperatures about freezing point ... I miss Australia

I got amp from Lenny8410; [email protected]

The price was $325 + postage. I will never know if his amp was bad or I just had problems somewhere else ... now it is not important any more because his amp served for spare parts to repair my amp. So ok, if I will need another one I will ask you for leo's address. When the buzzing sound will come again (hopefully not) I will try to locate its cause.
Adios.

 

[samosali]

I found out:

I tried to disconnect all audio connectors (10 poles or so) one by one but the buzzing did not stop. with radio or CD on the only thing which stops buzzing on all speakers is disconnecting of blue/white wire at tuner/amplifier A2/3. alldata says that this wire is control voltage which goes into left/right amplifier N40/3 (so the black box which is located above the tuner/amplifier).

So, I am still not sure which amplifier is damaged:
-tuner/amplifier A2/3 or
-left/right amplifier N40/3?

most probably the bad one is A2/3 I would say because N40/3 was just recently repaired. I assume head unit in the cabin is excluded from the list of culprits? any another idea?

 

[MikeJT]

Hi Somali,
I don't know anything much about car audio systems - I have limited interest in them - but one of the main causes of 50 Hz noise in a domestic hi-fi system is having too many ground connections, which can which cause ground loops. Clearly, you don't have 50 Hz in your car system but I'm sure that the same logic applies and you would pick up voltage differences in the cars 'grounding', which would have a 'noise' content.

One of the ways this can occur is if screened leads have their screens connected to ground at both ends when there is already a ground connection made to the device. This is particularly the case when the screened cable interconnects two devices which both have their own ground connection. The screen can now carry a small noise current - which gets added in to the signal current - when it should just be providing electrostatic screening. Disconnecting the screen at one end of such a lead can overcome such a problem.

I don't think you would normally find such problems with good, professional kit but I do wonder about your PO's box with the round connectors. Also, poor grounding at a unit can cause ground noise and, in principle, all units should be grounded very close together but this is obviously not always possible.

Noise can also be caused through electromagnetic induction if signal cables are run close to amplifier power cables.

Is the noise worse with the engine running or when car electromagnetic devices run, such as the PSE pump?

Mike

 

[samosali]

Hi Somali,
I don't know anything much about car audio systems - I have limited interest in them - but one of the main causes of 50 Hz noise in a domestic hi-fi system is having too many ground connections, which can which cause ground loops. Clearly, you don't have 50 Hz in your car system but I'm sure that the same logic applies and you would pick up voltage differences in the cars 'grounding', which would have a 'noise' content.

One of the ways this can occur is if screened leads have their screens connected to ground at both ends when there is already a ground connection made to the device. This is particularly the case when the screened cable interconnects two devices which both have their own ground connection. The screen can now carry a small noise current - which gets added in to the signal current - when it should just be providing electrostatic screening. Disconnecting the screen at one end of such a lead can overcome such a problem.

I don't think you would normally find such problems with good, professional kit but I do wonder about your PO's box with the round connectors. Also, poor grounding at a unit can cause ground noise and, in principle, all units should be grounded very close together but this is obviously not always possible.

Noise can also be caused through electromagnetic induction if signal cables are run close to amplifier power cables.

Is the noise worse with the engine running or when car electromagnetic devices run, such as the PSE pump?

Mike

Hi Mike, thanks for your reply.
I studied parts diagrams for MB (one russian site, proposed by syljua) and I found out that the box for which I thought it is PO's invention, is actually listed among the sound system equipment meant for my car. I also found out that there is many types of sound systems in our cars ... and because my car was made for West germany (in those times it existed) almost nobody from this forum can be familiar wih my particular case.

So, much of your hypothesis is not relevant any more in primary sense but of course what you claim can still be true.

I am 99,99% sure that it is not head unit because if I disconnect the connector HEAD UNIT- TUNER/AMPLIFIER the buzzing is still on.

I took the tuner/amplifier to the repair shop, I still think it has gone and the main cause is broken control voltage which connects pin 19 in amplifier (left/right BOSE amplifier). I wll report very soon about the results.

The point is that buzzing came on slowly and sometimes when I turned head unit OFF and On again, the buzzing went away but then it came on again in few minutes. When I dismounted the tuner/amplifier I noticed that the screw which holds it in a frame (which is on a fender) was loosen .... I hope that is not a reason??????

As for your question: I cannot see any correlation between buzzing and any device or engine.

 

[MikeJT]

As for your question: I cannot see any correlation between buzzing and any device or engine.

It sounds like some kind of non-linear vibration - it comes and goes. Any chance that there is some electro-mechanical coupling somewhere? Have you tried giving every unit, including the speakers, a 'tap' to see if that alters the buzzing at all? Or whether any audible buzzing is coming from a unit other than a louspeaker? - I'm thinking of buzz from a loose winding or core lamination - perhaps in a dc-to-dc convertor?

 

[syljua]

I studied parts diagrams for MB (one russian site, proposed by syljua) and I found out that the box for which I thought it is PO's invention, is actually listed among the sound system equipment meant for my car. I also found out that there is many types of sound systems in our cars ... and because my car was made for West germany (in those times it existed) almost nobody from this forum can be familiar wih my particular case.

Can you identify your boxes from the images on this page?;
Car Stereo Removal and Installation - Mecedes Benz S Class Bose Amplifier Removal - BOSE Car Stereo, Speaker / Amp Repair
or this?;
http://www.carstereohelp.com/mercedes.htm

br,
syljua

 

[samosali]

Can you identify your boxes from the images on this page?;
Car Stereo Removal and Installation - Mecedes Benz S Class Bose Amplifier Removal - BOSE Car Stereo, Speaker / Amp Repair
or this?;
Factory Car Audio Repair For All Makes and Models - Mercedes S/SL/SLK, C/CL/CLK, Car Stereo Repair Estimates and Bose Car Stereo, Speaker / Amp Repair

The first link shows a picture with two visible boxes: tuner/amplifier (A2/3) and amplifier (N40/3). The first one is the lower box. The quality of the picture is not good enough to identify another boxes if they are present at all.

In the second link I can see my head unit becker Mexico 2000 RDS and bose amplifier 140 820 00 89. Maybe the mercedes tuner box under the bose amplifier is like mine but I cannot be sure (Of course I have one tuner box but I think mine is 002 820 32 89).

beside those three boxes I have also Alpine CD player which is not shown in the links.

I attached the picture where my fifth box (CD amplifier) is under position 134.

 

[samosali]

local pro fixed my amp/tuner for 50 EUR. Now I am in the saddle again. I do not have a heart to put original stereo out and put some aftermarket devices in. it seems I am lucky to have good experts near me ... it seems they can repair everything.

by the way, the only critical factor in my system is now a "SEEK" button in head unit. sometimes i must press it twice to get any respond. is a contact spray into the slot around the button a good idea?

one additional question: can listening of radio stations in a car be compared with listening at static location? namely, I have impression that there is too many "ssss" and "hhhhhhhh" sounds during listening ....even when STEREO sign is on a display. is this normal?

 

[MikeJT]

local pro fixed my amp/tuner for 50 EUR. Now I am in the saddle again. I do not have a heart to put original stereo out and put some aftermarket devices in. it seems I am lucky to have good experts near me ... it seems they can repair everything.

by the way, the only critical factor in my system is now a "SEEK" button in head unit. sometimes i must press it twice to get any respond. is a contact spray into the slot around the button a good idea?

one additional question: can listening of radio stations in a car be compared with listening at static location? namely, I have impression that there is too many "ssss" and "hhhhhhhh" sounds during listening ....even when STEREO sign is on a display. is this normal?

Hi Samosali,

Out of curiosity, did your 'fixer' tell you what had been wrong previously?

As for spraying contact cleaner into the 'SEEK' button, while I'm a great proponent of these products, I believe you had a bad experience previously when using it on your a/c controller. So I don't know what your product contained. Secondly, the buttons on some of these types of units use conducting rubber pads to bridge a pair of contacts. I think this provides a fairly high impedance input to the microprocessor rather than being a traditional switch. I don't think contact cleaner would make much difference in this case. Some others use miniature, sealed switches mounted on the pcb immediately behind the button and I doubt whether you would get any cleaner in there without absolutely flooding it - which is probably a bad idea.

As for your radio interference, I would guess that it's down to signal strength. Have you tried it statically at a location where you know that you can normally get good reception, e.g. outside where you live?

Mike

 

[samosali]

Out of curiosity, did your 'fixer' tell you what had been wrong previously?

As for spraying contact cleaner into the 'SEEK' button, while I'm a great proponent of these products, I believe you had a bad experience previously when using it on your a/c controller. So I don't know what your product contained. Secondly, the buttons on some of these types of units use conducting rubber pads to bridge a pair of contacts. I think this provides a fairly high impedance input to the microprocessor rather than being a traditional switch. I don't think contact cleaner would make much difference in this case. Some others use miniature, sealed switches mounted on the pcb immediately behind the button and I doubt whether you would get any cleaner in there without absolutely flooding it - which is probably a bad idea.

As for your radio interference, I would guess that it's down to signal strength. Have you tried it statically at a location where you know that you can normally get good reception, e.g. outside where you live?

Hi Mike,

no, the fixer did not tell me anything. I just know that they tried for several days to find a mistake. Maybe it is not true ... maybe "some days" means "some minutes" every day.

Ok for contact cleaner , thanks for your suggestions. i will not use it. when some more serious mistake will occur in my head unit (burned bulb or something) I will get it out and give it to professionals to fix also the button.

as for radio; statically the sound is good, no problems at all. I must admit that I did not make a deep analysis of the problem; so which stations have noisy moments ... what is a position of a car in that moment, etc. I just realized that listening to my radio during a drive is not a joy for a person who cares about the sound. beside that I think in my wife's car with radio for about 100 EUR the radio stations are more clear. So, what are your experiences with this (do you also have better signal when staying on a place than when driving)? thanks and best regards.

 

[MikeJT]

I would say that exaggerated sibilant sounds - like 'ssss' - is usually a sign of poor fm signal strength - I don't know what the technical reason is but, in my experience, it's the high frequencies that get affected most . I only experience it when driving 80 km, say, from London as I need to retune to another transmitter (can happen automatically), or when driving in a hilly area listening to a weaker station.

I don't know where you are in Slovenia but I believe it's quite a hilly country, so maybe the signal strength varies a lot as you drive around (I did actually drive in your country as a student and it must be nearly 50 years ago - ah, me, vita brevis!). And maybe your wife's car has a better aerial!

Mike